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SAO/NASA ADS Astronomy Abstract Service

Title:
The Hinode X-Ray Telescope (XRT): Camera Design, Performance and Operations
Authors:
Kano, R.; Sakao, T.; Hara, H.; Tsuneta, S.; Matsuzaki, K.; Kumagai, K.; Shimojo, M.; Minesugi, K.; Shibasaki, K.; Deluca, E. E.; Golub, L.; Bookbinder, J.; Caldwell, D.; Cheimets, P.; Cirtain, J.; Dennis, E.; Kent, T.; Weber, M.
Affiliation:
AA(National Astronomical Observatory of Japan), AB(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), AC(National Astronomical Observatory of Japan), AD(National Astronomical Observatory of Japan), AE(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), AF(National Astronomical Observatory of Japan), AG(Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan), AH(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), AI(Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan), AJ(Smithsonian Astrophysical Observatory), AK(Smithsonian Astrophysical Observatory), AL(Smithsonian Astrophysical Observatory), AM(Smithsonian Astrophysical Observatory), AN(Smithsonian Astrophysical Observatory), AO(Smithsonian Astrophysical Observatory), AP(Smithsonian Astrophysical Observatory), AQ(Smithsonian Astrophysical Observatory), AR(Smithsonian Astrophysical Observatory)
Publication:
Solar Physics, Volume 249, Issue 2, pp.263-279 (SoPh Homepage)
Publication Date:
06/2008
Origin:
SPRINGER
Keywords:
Sun: corona, Sun: X-rays
Abstract Copyright:
(c) 2008: Springer Science+Business Media B.V.
DOI:
10.1007/s11207-007-9058-7
Bibliographic Code:
2008SoPh..249..263K

Abstract

The X-ray Telescope (XRT) aboard the Hinode satellite is a grazing incidence X-ray imager equipped with a 2048×2048 CCD. The XRT has 1 arcsec pixels with a wide field of view of 34×34 arcmin. It is sensitive to plasmas with a wide temperature range from < 1 to 30 MK, allowing us to obtain TRACE-like low-temperature images as well as Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data Processor (MDP) controls the XRT through sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection, and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field of view for a given telemetry bandwidth. With a focus adjust mechanism, a higher resolution of Gaussian focus may be available on-axis. This paper follows the first instrument paper for the XRT (Golub et al., Solar Phys. 243, 63, <CitationRef CitationID="CR4">2007</CitationRef>) and discusses the design and measured performance of the X-ray CCD camera for the XRT and its control system with the MDP.

Title:
Modeling Nonpotential Magnetic Fields in Solar Active Regions
Authors:
Bobra, M. G.; van Ballegooijen, A. A.; DeLuca, E. E.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138)
Publication:
The Astrophysical Journal, Volume 672, Issue 2, pp. 1209-1220. (ApJ Homepage)
Publication Date:
01/2008
Origin:
UCP
ApJ Keywords:
Sun: Corona, Sun: Magnetic Fields
Abstract Copyright:
(c) 2008: The American Astronomical Society
DOI:
10.1086/523927
Bibliographic Code:
2008ApJ...672.1209B

Abstract

Electric currents are present in the coronae above solar active regions, producing nonpotential magnetic fields that can be approximated as nonlinear force-free fields (NLFFFs). In this paper NLFFF models for two active regions observed in 2002 June are presented. The models are based on magnetograms from SOHO MDI and are constrained by nonpotential structures seen in BBSO Hα images and TRACE EUV images. The models are constructed using the flux rope insertion method. We find that the axial fluxes of the flux ropes are well constrained by the observations. The flux ropes are only weakly twisted, and electric currents flow mainly at the interface between the flux rope and its surroundings. In one case, the flux rope is anchored with both ends in the active region; in the other case, the flux rope extends to the neighboring quiet Sun. We find that the magnetic fields in these active regions are close to an eruptive state: the axial flux in the flux ropes is close to the upper limit for eruption. We also derive estimates for magnetic free energy and helicity in these regions.

Title:
Slipping Magnetic Reconnection in Coronal Loops
Authors:
Aulanier, Guillaume; Golub, Leon; DeLuca, Edward E.; Cirtain, Jonathan W.; Kano, Ryouhei; Lundquist, Loraine L.; Narukage, Noriyuki; Sakao, Taro; Weber, Mark A.
Affiliation:
AA(Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie (UPMC), Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France.), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AD(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AE(National Astronomical Observatory of Japan (NAOJ), Mitaka, Tokyo 181–8588, Japan.), AF(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AG(Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607–8471, Japan.), AH(Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.), AI(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.)
Publication:
Science, Volume 318, Issue 5856, pp. 1588- (2007).
Publication Date:
12/2007
Category:
ASTRONOMY
Origin:
SCIENCE
Abstract Copyright:
(c) 2007: Science
DOI:
10.1126/science.1146143
Bibliographic Code:
2007Sci...318.1588A

Abstract

Magnetic reconnection of solar coronal loops is the main process that causes solar flares and possibly coronal heating. In the standard model, magnetic field lines break and reconnect instantaneously at places where the field mapping is discontinuous. However, another mode may operate where the magnetic field mapping is continuous but shows steep gradients: The field lines may slip across each other. Soft x-ray observations of fast bidirectional motions of coronal loops, observed by the Hinode spacecraft, support the existence of this slipping magnetic reconnection regime in the Sun’s corona. This basic process should be considered when interpreting reconnection, both on the Sun and in laboratory-based plasma experiments.

Title:
Continuous Plasma Outflows from the Edge of a Solar Active Region as a Possible Source of Solar Wind
Authors:
Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku, Jun'ichi; Bando, Takamasa; DeLuca, Edward E.; Lundquist, Loraine L.; Tsuneta, Saku; Harra, Louise K.; Katsukawa, Yukio; Kubo, Masahito; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay A.; Golub, Leon; Korreck, Kelly E.; Su, Yingna; Shibasaki, Kiyoto; Shimizu, Toshifumi; Nakatani, Ichiro
Affiliation:
AA(Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.), AB(National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.), AC(Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.), AD(National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.), AE(National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.), AF(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.), AG(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.), AH(National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.), AI(University College London (UCL)–Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK.), AJ(National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.), AK(High Altitude Observatory, National Center for Atmospheric Research (NCAR), Post Office Box 3000, Boulder, CO 80307–3000, USA.), AL(National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan.), AM(Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.), AN(Nobeyama Radio Observatory, NAOJ, 462-2 Nobeyama, Minamimaki, Minamisaku, Nagano 384–1305, Japan.), AO(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.), AP(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.), AQ(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.), AR(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 58, Cambridge, MA 02138, USA.), AS(Nobeyama Radio Observatory, NAOJ, 462-2 Nobeyama, Minamimaki, Minamisaku, Nagano 384–1305, Japan.), AT(Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.), AU(Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229–8510, Japan.)
Publication:
Science, Volume 318, Issue 5856, pp. 1585- (2007).
Publication Date:
12/2007
Category:
ASTRONOMY
Origin:
SCIENCE
Abstract Copyright:
(c) 2007: Science
DOI:
10.1126/science.1147292
Bibliographic Code:
2007Sci...318.1585S

Abstract

The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to ~1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.

Title:
Evidence for Alfvén Waves in Solar X-ray Jets
Authors:
Cirtain, J. W.; Golub, L.; Lundquist, L.; van Ballegooijen, A.; Savcheva, A.; Shimojo, M.; DeLuca, E.; Tsuneta, S.; Sakao, T.; Reeves, K.; Weber, M.; Kano, R.; Narukage, N.; Shibasaki, K.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.; Marshall Space Flight Center, National Aeronautics and Space Administration (NASA) VP62, Huntsville, AL 35812, USA.), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AD(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AE(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AF(Nobeyama Solar Radio Observatory, Nobeyama, Nagano 384–1305, Japan.), AG(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AH(National Astronomical Observatory of Japan (NAOJ), Mitaka, Tokyo 181–8588, Japan.), AI(Institute of Space and Astronautical Science, (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa 229–8510, Japan.), AJ(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AK(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.), AL(National Astronomical Observatory of Japan (NAOJ), Mitaka, Tokyo 181–8588, Japan.), AM(Institute of Space and Astronautical Science, (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa 229–8510, Japan.), AN(Nobeyama Solar Radio Observatory, Nobeyama, Nagano 384–1305, Japan.)
Publication:
Science, Volume 318, Issue 5856, pp. 1580- (2007).
Publication Date:
12/2007
Category:
ASTRONOMY
Origin:
SCIENCE
Abstract Copyright:
(c) 2007: Science
DOI:
10.1126/science.1147050
Bibliographic Code:
2007Sci...318.1580C

Abstract

Coronal magnetic fields are dynamic, and field lines may misalign, reassemble, and release energy by means of magnetic reconnection. Giant releases may generate solar flares and coronal mass ejections and, on a smaller scale, produce x-ray jets. Hinode observations of polar coronal holes reveal that x-ray jets have two distinct velocities: one near the Alfvén speed (~800 kilometers per second) and another near the sound speed (200 kilometers per second). Many more jets were seen than have been reported previously; we detected an average of 10 events per hour up to these speeds, whereas previous observations documented only a handful per day with lower average speeds of 200 kilometers per second. The x-ray jets are about 2 × 103 to 2 × 104 kilometers wide and 1 × 105 kilometers long and last from 100 to 2500 seconds. The large number of events, coupled with the high velocities of the apparent outflows, indicates that the jets may contribute to the high-speed solar wind.

Title:
An On-Orbit Determination of the On-Axis Point Spread Function of the Hinode X-Ray Telescope
Authors:
Weber, M.; Deluca, E. E.; Golub, L.; Cirtain, J.; Kano, R.; Sakao, T.; Shibasaki, K.; Narukage, N.
Publication:
Publications of the Astronomical Society of Japan, Vol.59, No.s3, pp.S853--S855 (PASJ Homepage)
Publication Date:
11/2007
Origin:
PASJ
Abstract Copyright:
(c) 2007: Astronomical Society of Japan
Bibliographic Code:
2007PASJ...59S.853W

Abstract

Not Available

Title:
Hinode Calibration for Precise Image Co-Alignment between SOT and XRT (2006 November-2007 April)
Authors:
Shimizu, T.; Katsukawa, Y.; Matsuzaki, K.; Ichimoto, K.; Kano, R.; Deluca, E. E.; Lundquist, L. L.; Weber, M.; Tarbell, T. D.; Shine, R. A.; Sôma, M.; Tsuneta, S.; Sakao, T.; Minesugi, K.
Publication:
Publications of the Astronomical Society of Japan, Vol.59, No.s3, pp.S845--S852 (PASJ Homepage)
Publication Date:
11/2007
Origin:
PASJ
Abstract Copyright:
(c) 2007: Astronomical Society of Japan
Bibliographic Code:
2007PASJ...59S.845S

Abstract

To understand the physical mechanisms for activity and heating in the solar atmosphere, the magnetic coupling from the photosphere to the corona is an important piece of information from the Hinode observations, and therefore precise positional alignment is required among the data acquired by different telescopes. The Hinode spacecraft and its onboard telescopes were developed to allow us to investigate magnetic coupling with co-alignment accuracy better than 1 arcsec. Using the Mercury transit observed on 8 November 2006 and co-alignment measurements regularly performed on a weekly basis, we have determined the information necessary for precise image co-alignment and have confirmed that co-alignment better than 1 arcsec can be realized between Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our baseline co-alignment method. This paper presents results from the calibration for precise co-alignment of CCD images from SOT and XRT.

Title:
Evolution of the Sheared Magnetic Fields of Two X-Class Flares Observed by Hinode/XRT
Authors:
Su, Y.; Golub, L.; van Ballegooijen, A.; Deluca, E. E.; Reeves, K. K.; Sakao, T.; Kano, R.; Narukage, N.; Shibasaki, K.
Publication:
Publications of the Astronomical Society of Japan, Vol.59, No.s3, pp.S785--S791 (PASJ Homepage)
Publication Date:
11/2007
Origin:
PASJ
Abstract Copyright:
(c) 2007: Astronomical Society of Japan
Bibliographic Code:
2007PASJ...59S.785S

Abstract

Not Available

Title:
A Study of Polar Jet Parameters Based on Hinode XRT Observations
Authors:
Savcheva, A.; Cirtain, J.; Deluca, E. E.; Lundquist, L. L.; Golub, L.; Weber, M.; Shimojo, M.; Shibasaki, K.; Sakao, T.; Narukage, N.; Tsuneta, S.; Kano, R.
Publication:
Publications of the Astronomical Society of Japan, Vol.59, No.s3, pp.S771--S778 (PASJ Homepage)
Publication Date:
11/2007
Origin:
PASJ
Abstract Copyright:
(c) 2007: Astronomical Society of Japan
Bibliographic Code:
2007PASJ...59S.771S

Abstract

Not Available

Title:
Magnetic Feature and Morphological Study of X-Ray Bright Points with Hinode
Authors:
Kotoku, J.; Kano, R.; Tsuneta, S.; Katsukawa, Y.; Shimizu, T.; Sakao, T.; Shibasaki, K.; Deluca, E. E.; Korreck, K. E.; Golub, L.; Bobra, M.
Publication:
Publications of the Astronomical Society of Japan, Vol.59, No.s3, pp.S735--S743 (PASJ Homepage)
Publication Date:
11/2007
Origin:
PASJ
Abstract Copyright:
(c) 2007: Astronomical Society of Japan
Bibliographic Code:
2007PASJ...59S.735K

Abstract

Not Available

Title:
What Determines the Intensity of Solar Flare/CME Events?
Authors:
Su, Yingna; Van Ballegooijen, Adriaan; McCaughey, James; Deluca, Edward; Reeves, Katharine K.; Golub, Leon
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138.; Purple Mountain Observatory, Nanjing, 210008, China; and Graduate University of Chinese Academy of Sciences, China.), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138.), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138.), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138.), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138.), AF(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138.)
Publication:
The Astrophysical Journal, Volume 665, Issue 2, pp. 1448-1459. (ApJ Homepage)
Publication Date:
08/2007
Origin:
UCP
ApJ Keywords:
Sun: Corona, Sun: Coronal Mass Ejections (CMEs), Sun: Flares, Sun: Magnetic Fields, Sun: Photosphere
Abstract Copyright:
(c) 2007: The American Astronomical Society
DOI:
10.1086/519679
Bibliographic Code:
2007ApJ...665.1448S

Abstract

We present a comprehensive statistical study addressing the question of what determines the intensity of a solar flare and associated coronal mass ejection (CME). For a sample of 18 two-ribbon flares associated with CMEs, we have examined the correlations between the GOES soft X-ray peak flare flux (PFF), the CME speed (VCME) obtained from SOHO LASCO observations, and six magnetic parameters of the flaring active region. These six parameters measured from both TRACE and SOHO MDI observations are: the average background magnetic field strength (B), the area of the region where B is counted (S), the magnetic flux of this region (Φ), the initial shear angle (θ1, measured at the flare onset), the final shear angle (θ2, measured at the time when the shear change stops), and the change of shear angle (θ12=θ1-θ2) of the footpoints. We have found no correlation between θ1 and the intensity of flare/CME events, while the other five parameters are either positively or negatively correlated with both log10(PFF) and VCME. Among these five parameters, Φ and θ12 show the most significant correlations with log10(PFF) and VCME. The fact that both log10(PFF) and VCME are highly correlated with θ12 rather than with θ1 indicates that the intensity of flare/CME events may depend on the released magnetic free energy rather than the total free energy stored prior to the flare. We have also found that a linear combination of a subset of these six parameters shows a much better correlation with the intensity of flare/CME events than each parameter itself, and the combination of log10Φ, θ1, and θ12 is the top-ranked combination.

Title:
Data Archive of the Hinode Mission
Authors:
Matsuzaki, K.; Shimojo, M.; Tarbell, T. D.; Harra, L. K.; Deluca, E. E.
Affiliation:
AA(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), AB(Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan), AC(Lockheed Martin Solar and Astrophysics Laboratory), AD(UCL Mullard Space Science Laboratory, Holmbury St. Mary), AE(Smithsonian Astrophysical Observatory)
Publication:
Solar Physics, Volume 243, Issue 1, pp.87-92 (SoPh Homepage)
Publication Date:
06/2007
Origin:
SPRINGER
Abstract Copyright:
(c) 2007: Springer
DOI:
10.1007/s11207-006-0303-2
Bibliographic Code:
2007SoPh..243...87M

Abstract

All of the Hinode telemetry data are to be reformatted and archived in the DARTS system at ISAS and mirrored to data centers around the word. The archived data are distributed to users through the Internet. This paper gives an overview of the files in the archive, including the file formats. All formats are portable and have heritage from the previous missions. From the reformatted files, index information is created for faster data search. Users can perform queries based on information contained in the index. This allows for searches to return observations that conform to particular observing conditions.

Title:
The X-Ray Telescope (XRT) for the Hinode Mission
Authors:
Golub, L.; Deluca, E.; Austin, G.; Bookbinder, J.; Caldwell, D.; Cheimets, P.; Cirtain, J.; Cosmo, M.; Reid, P.; Sette, A.; Weber, M.; Sakao, T.; Kano, R.; Shibasaki, K.; Hara, H.; Tsuneta, S.; Kumagai, K.; Tamura, T.; Shimojo, M.; McCracken, J.; Carpenter, J.; Haight, H.; Siler, R.; Wright, E.; Tucker, J.; Rutledge, H.; Barbera, M.; Peres, G.; Varisco, S.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics), AB(Harvard-Smithsonian Center for Astrophysics), AC(Harvard-Smithsonian Center for Astrophysics), AD(Harvard-Smithsonian Center for Astrophysics), AE(Harvard-Smithsonian Center for Astrophysics), AF(Harvard-Smithsonian Center for Astrophysics), AG(Harvard-Smithsonian Center for Astrophysics), AH(Harvard-Smithsonian Center for Astrophysics), AI(Harvard-Smithsonian Center for Astrophysics), AJ(Harvard-Smithsonian Center for Astrophysics), AK(Harvard-Smithsonian Center for Astrophysics), AL(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), AM(National Astronomical Observatory), AN(Nobeyama Solar Radio Observatory, National Astronomical Observatory), AO(National Astronomical Observatory), AP(National Astronomical Observatory), AQ(National Astronomical Observatory), AR(National Astronomical Observatory), AS(Nobeyama Solar Radio Observatory, National Astronomical Observatory), AT(NASA/Marshall Space Flight Center), AU(NASA/Marshall Space Flight Center), AV(NASA/Marshall Space Flight Center), AW(NASA/Marshall Space Flight Center), AX(NASA/Marshall Space Flight Center), AY(NASA/Marshall Space Flight Center), AZ(NASA/Marshall Space Flight Center), BA(Osservatorio Astronomico di Palermo “G.S. Vaiana”), BB(Osservatorio Astronomico di Palermo “G.S. Vaiana”), BC(Osservatorio Astronomico di Palermo “G.S. Vaiana”)
Publication:
Solar Physics, Volume 243, Issue 1, pp.63-86 (SoPh Homepage)
Publication Date:
06/2007
Origin:
SPRINGER
Abstract Copyright:
(c) 2007: Springer
DOI:
10.1007/s11207-007-0182-1
Bibliographic Code:
2007SoPh..243...63G

Abstract

The X-ray Telescope (XRT) of the Hinode mission provides an unprecedented combination of spatial and temporal resolution in solar coronal studies. The high sensitivity and broad dynamic range of XRT, coupled with the spacecraft’s onboard memory capacity and the planned downlink capability will permit a broad range of coronal studies over an extended period of time, for targets ranging from quiet Sun to X-flares. This paper discusses in detail the design, calibration, and measured performance of the XRT instrument up to the focal plane. The CCD camera and data handling are discussed separately in a companion paper.

Title:
Coronal Diagnostic Spectrometer Observations of Isothermal and Multithermal Coronal Loops
Authors:
Schmelz, J. T.; Nasraoui, K.; Del Zanna, G.; Cirtain, J. W.; DeLuca, E. E.; Mason, H. E.
Affiliation:
AA(Physics Department, University of Memphis, Memphis, TN 38152; ), AB(Physics Department, University of Memphis, Memphis, TN 38152; ), AC(Physics Department, University of Memphis, Memphis, TN 38152; University of College London, Department of Space and Climate Physics, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT UK; .), AD(Physics Department, University of Memphis, Memphis, TN 38152; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; ), AE(Physics Department, University of Memphis, Memphis, TN 38152; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; .), AF(Physics Department, University of Memphis, Memphis, TN 38152)
Publication:
The Astrophysical Journal, Volume 658, Issue 2, pp. L119-L122. (ApJ Homepage)
Publication Date:
04/2007
Origin:
UCP
ApJ Keywords:
Sun: Corona, Sun: Fundamental Parameters, Sun: UV Radiation
Abstract Copyright:
(c) 2007: The American Astronomical Society
DOI:
10.1086/514815
Bibliographic Code:
2007ApJ...658L.119S

Abstract

A data set obtained on 2003 January 17 with the Coronal Diagnostic Spectrometer (CDS) shows two loops sitting side by side on the solar disk. These loops are oriented along the CDS slit, so all pixels in each loop were observed simultaneously. So, although the instrument has a relatively slow time cadence, changes as a function of time that may occur during the CDS raster buildup will not affect the loop temperature results. Differential emission measure (DEM) analysis using a forward-folding technique shows different results for the two loops. For the first loop, the intensities of the lines that remain after background subtraction are well fit with a DEM curve that collapses to a single spike. In other words, the loop plasma at this location is isothermal. This analysis is confirmed with an emission measure loci method and agrees with the results obtained recently by other authors that show that the moderate spatial resolution of CDS can detect isothermal structures. For the second loop, the background-subtracted line intensities require a broad DEM, not consistent with isothermal plasma. This conclusion is confirmed with an automatic-inversion DEM method. In this Letter, we specifically address some of the concerns raised about CDS temperature analysis: the slow CDS temporal resolution, the moderate CDS spatial resolution, the inherent smoothing associated with DEM inversion, and line-of-sight effects on the DEM distribution.

Title:
Active Region Loops: Temperature Measurements as a Function of Time from Joint TRACE and SOHO CDS Observations
Authors:
Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.; Martens, P. C. H.; Schmelz, J. T.
Affiliation:
AA(University College London, Department of Space and Climate Physics, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, UK; ), AB(University College London, Department of Space and Climate Physics, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, UK), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; DAMTP, Centre for Mathematical Sciences, Cambridge, UK.), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; Montana State University, Department of Physics, Bozeman, MT.), AF(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Publication:
The Astrophysical Journal, Volume 655, Issue 1, pp. 598-605. (ApJ Homepage)
Publication Date:
01/2007
Origin:
UCP
ApJ Keywords:
Sun: Corona, Sun: UV Radiation
Abstract Copyright:
(c) 2007: The American Astronomical Society
DOI:
10.1086/509769
Bibliographic Code:
2007ApJ...655..598C

Abstract

In this paper, we aim to quantitatively investigate the structure and time variation of quiescent active region loop structures. We coordinated a joint program of observations (JOP 146) using TRACE, to obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic data. Loop intensities are used to determine temperature as a function of time for a single loop, taking full account of the background emission. In many locations, the emission measure loci are consistent with an isothermal structure. However, the results indicate significant changes in the loop temperature (between 1 and 2 MK) over the 6 hr observing period. It is possible that the loop structures are composed of multiple, independently heated strands with sizes less than the resolution of the imager and spectrometer.

Title:
Companion Event and Precursor of the X17 Flare on 28 October 2003
Authors:
Mandrini, C. H.; Demoulin, P.; Schmieder, B.; Deluca, E. E.; Pariat, E.; Uddin, W.
Affiliation:
AA(Instituto de Astronomía y Física del Espacio (IAFE), CONICET-UBA), AB(Observatoire de Paris, LESIA, FRE 2461 (CNRS)), AC(Observatoire de Paris, LESIA, FRE 2461 (CNRS)), AD(Smithsonian Astrophysical Observatory (SAO)), AE(Observatoire de Paris, LESIA, FRE 2461 (CNRS)), AF(Aryabhatta Research Institute of Observational Sciences (ARIES))
Publication:
Solar Physics, Volume 238, Issue 2, pp.293-312 (SoPh Homepage)
Publication Date:
11/2006
Origin:
SPRINGER
Abstract Copyright:
(c) 2006: Springer Science + Business Media, Inc.
DOI:
10.1007/s11207-006-0205-3
Bibliographic Code:
2006SoPh..238..293M

Abstract

A major two-ribbon X17 flare occurred on 28 October 2003, starting at 11:01 UT in active region NOAA 10486. This flare was accompanied by the eruption of a filament and by one of the fastest halo coronal mass ejections registered during the October November 2003 strong activity period. We focus on the analysis of magnetic field (SOHO/MDI), chromospheric (NainiTal observatory and TRACE), and coronal (TRACE) data obtained before and during the 28 October event. By combining our data analysis with a model of the coronal magnetic field, we concentrate on the study of two events starting before the main flare. One of these events, evident in TRACE images around one hour prior to the main flare, involves a localized magnetic reconnection process associated with the presence of a coronal magnetic null point. This event extends as long as the major flare and we conclude that it is independent from it. A second event, visible in Hα and TRACE images, simultaneous with the previous one, involves a large-scale quadrupolar reconnection process that contributes to decrease the magnetic field tension in the overlaying field configuration; this allows the filament to erupt in a way similar to that proposed by the breakout model, but with magnetic reconnection occurring at Quasi-Separatrix Layers (QSLs) rather than at a magnetic null point.

Title:
Magnetic reconfiguration before the X 17 Solar flare of October 28 2003
Authors:
Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Pariat, E.; Berlicki, A.; Deluca, E.
Affiliation:
AA(Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon Cedex, France; ITA, P.O. Box 1029, Blindern, N-0315 Oslo, Norway), AB(IAFE, CONICET-UBA, CC67, Suc 28, 1428 Buenos Aires, Argentina), AC(Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon Cedex, France), AD(Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon Cedex, France), AE(Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique (LESIA), Observatoire de Paris, 5 place Jules Janssen, F-92195 Meudon Cedex, France), AF(Smithsonian Astrophysical Observatory, 60 Garden Street, MS58, Cambridge, MA 02138, USA)
Publication:
Advances in Space Research, Volume 37, Issue 7, p. 1313-1316. (AdSpR Homepage)
Publication Date:
00/2006
Origin:
ELSEVIER
Abstract Copyright:
COSPAR
DOI:
10.1016/j.asr.2004.12.051
Bibliographic Code:
2006AdSpR..37.1313S

Abstract

An active region (AR) NOAA 10486, which produced a large number of X-ray flares during October November 2003, was observed during a multi-wavelength campaign with ground based and space instruments. We focus our analysis on the observations of October 28, 2003. The magnetic field was observed with THEMIS (Na D1) and MDI (Ni I), the chromosphere with THEMIS (Ca II 8542 Å) and with the Meudon heliograph in Hα, the EUV images with SOHO/EIT and TRACE. Two pre-events started just before the major X 17 flare. One was related to localized flux emergence and lasted until the decay phase of the X flare; while the second one involved a large scale quadrupolar reconnection, that we infer by modeling the AR magnetic field. Extended dimming areas across the equator (EIT), large arcades of post-flare loops (TRACE 195 Å) and a halo CME (LASCO) were observed consequently after the flare. We perform an extrapolation of the magnetic field above the photosphere using a linear force-free-field approximation that allows us to find the connectivity among the four polarities that would be involved in the quadrupolar reconnection event. The X 17 flare is plausibly due to the destabilisation of a twisted flux tube, the bottom part of this magnetic structure can be visualized by the presence of a filament. The destabilization is caused by converging and shearing photospheric motions towards the main magnetic inversion line. The large scale quadrupolar reconnection related to the second pre-event would favour the opening of the field above the twisted flux tube and, consequently, the coronal mass ejection.

Title:
Isothermal Bias of the ``Filter Ratio'' Method for Observations of Multithermal Plasma
Authors:
Weber, M. A.; Schmelz, J. T.; DeLuca, E. E.; Roames, J. K.
Affiliation:
AA(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138; , .), AB(Physics Department, University of Memphis, Memphis, TN 38152; , .), AC(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138; , .), AD(Physics Department, University of Memphis, Memphis, TN 38152; , .)
Publication:
The Astrophysical Journal, Volume 635, Issue 1, pp. L101-L104. (ApJ Homepage)
Publication Date:
12/2005
Origin:
UCP
ApJ Keywords:
Methods: Data Analysis, Sun: Corona, Sun: UV Radiation
Abstract Copyright:
(c) 2005: The American Astronomical Society
DOI:
10.1086/499125
Bibliographic Code:
2005ApJ...635L.101W

Abstract

An early result from the Transition Region and Coronal Explorer (TRACE) was that the EUV filter ratios for many narrow coronal loops (widths of a few arcseconds) were found to cluster within the small range 0.50-1.70, as functions of position along loop length. The most common interpretation is that the temperature along the loop is in fact nearly constant with a value between 1.1 and 1.3 MK. This interpretation has resulted in a class of TRACE loop models with heating close to the footpoints. We analyze the filter ratio method to show that the constant TRACE 195 Å/173 Å ratios can be reproduced by multithermal differential emission measures (DEMs) along the line of sight over a wide range of peak temperatures, so long as the distribution is relatively flat and spans the temperature response of both channels. Furthermore, in the limit of flat (i.e., very multithermal) DEMs, the filter ratio method is biased toward the ratio of the integrals of the temperature response functions. This result is general to any measurement of intensity ratios that are formed over a nonzero temperature range (e.g., narrow passbands and ion emission lines).

Title:
Science of the X-ray Sun: The X-ray telescope on Solar-B
Authors:
Deluca, E. E.; Weber, M. A.; Sette, A. L.; Golub, L.; Shibasaki, K.; Sakao, T.; Kano, R.
Affiliation:
AA(High Energy Astrophysics, Harvard-Smithsonian Center for Astrophysics, MS 58, 60 Garden St., Cambridge, MA 02138, USA), AB(High Energy Astrophysics, Harvard-Smithsonian Center for Astrophysics, MS 58, 60 Garden St., Cambridge, MA 02138, USA; Tel.: +1 1617 495 7139.), AC(High Energy Astrophysics, Harvard-Smithsonian Center for Astrophysics, MS 58, 60 Garden St., Cambridge, MA 02138, USA), AD(High Energy Astrophysics, Harvard-Smithsonian Center for Astrophysics, MS 58, 60 Garden St., Cambridge, MA 02138, USA), AE(Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Nagano 384-1305, Japan), AF(National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan), AG(National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan)
Publication:
Advances in Space Research, Volume 36, Issue 8, p. 1489-1493. (AdSpR Homepage)
Publication Date:
00/2005
Origin:
ELSEVIER
Abstract Copyright:
COSPAR
DOI:
10.1016/j.asr.2004.12.073
Bibliographic Code:
2005AdSpR..36.1489D

Abstract

The X-Ray Telescope (XRT) on Solar-B is designed to provide high resolution, high cadence observations of the X-ray corona through a wide range of filters. The XRT science team has identified four general problems in coronal physics as the primary science goals for our instrument. Each of these goals will require collaborative observations from the other Solar-B instruments: EUV Imaging Spectrograph (EIS) and Solar Optical Telescope Focal Plane Package (SOT). We will discuss the science goals and observations needed to address those goals.

Title:
Magnetic changes observed in the formation of two filaments in a complex active region: TRACE and MSDP observations
Authors:
Schmieder, Brigitte; Mein, Nicole; Deng, Yuanyong; Dumitrache, Cristiana; Malherbe, Jean-Marie; Staiger, Joachim; Deluca, E. E.
Affiliation:
AA(Observatoire de Paris; Institute of Theoretical Astrophysics, University of Oslo), AB(Observatoire de Paris), AC(Beijing Astronomical Observatory, Chinese Academy of Sciences), AD(Astronomical Institut of Romanian Academy), AE(Observatoire de Paris), AF(Kiepenheuer Institut für Sonnenphysik), AG(Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics)
Publication:
Solar Physics, Volume 223, Issue 1-2, pp. 119-141 (SoPh Homepage)
Publication Date:
09/2004
Origin:
SPRINGER
Abstract Copyright:
(c) 2004: Kluwer Academic Publishers
DOI:
10.1007/s11207-004-1107-x
Bibliographic Code:
2004SoPh..223..119S

Abstract

This paper is focused on the formation of two filaments in a complex center of decaying active regions (AR 8329 and AR 8326), located in the northern hemisphere. The observations were obtained in Hα by the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted on the German telescope VTT in Tenerife) and EUV lines with TRACE (Transition Region And Corona Explorer). High Doppler shifts are found to be related to the ends of filament segments where canceling magnetic fields are also located (as seen on magnetograms from Big Bear Solar Observatory). At these locations, velocities along the line of sight, derived by using a cloud model method reach ‑20 km s‑1, the segments of filaments merge and frequently a time-related sub-flare is observed by TRACE. The chirality of the filament segments has been determined by different methods: the segments of dextral chirality join together and form a long dextral filament, and a single filament of sinistral chirality forms end to end with the dextral filament but does not merge with it. Assuming a model of twisted flux tube for filament material, we suggest that the dextral filament has negative helicity and a relationship between its formation and the close by sunspot with the same sign of helicity.

Title:
Characteristics of transverse oscillations in a coronal loop arcade
Authors:
Verwichte, E.; Nakariakov, V. M.; Ofman, L.; Deluca, E. E.
Affiliation:
AA(Department of Physics, University of Warwick), AB(Department of Physics, University of Warwick), AC(Catholic University of America/NASA Goddard Space Flight Center, Code 682), AD(Harvard-Smithsonian Center for Astrophysics)
Publication:
Solar Physics, Volume 223, Issue 1-2, pp. 77-94 (SoPh Homepage)
Publication Date:
09/2004
Origin:
SPRINGER
Abstract Copyright:
(c) 2004: Kluwer Academic Publishers
DOI:
10.1007/s11207-004-0807-6
Bibliographic Code:
2004SoPh..223...77V

Abstract

TRACE observations from 15 April 2001 of transverse oscillations in coronal loops of a post-flare loop arcade are investigated. They are considered to be standing fast kink oscillations. Oscillation signatures such as displacement amplitude, period, phase and damping time are deduced from 9 loops as a function of distance along the loop length. Multiple oscillation modes are found with different amplitude profile along the loop length, suggesting the presence of a second harmonic. The damping times are consistent with the hypothesis of phase mixing and resonant absorption, although there is a clear bias towards longer damping times compared with previous studies. The coronal magnetic field strength and coronal shear viscosity in the loop arcade are derived.

Title:
Detection of X-Ray Resonance Scattering in Active Stellar Coronae
Authors:
Testa, Paola; Drake, Jeremy J.; Peres, Giovanni; DeLuca, Edward E.
Affiliation:
AA(Smithsonian Astrophysical Observatory (SAO), MS 3, 60 Garden Street, Cambridge, MA 02138; .; SAO Predoctoral Fellow.; Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo Piazza del Parlamento 1, 90134 Palermo, Italy.), AB(Smithsonian Astrophysical Observatory (SAO), MS 3, 60 Garden Street, Cambridge, MA 02138; .), AC(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo Piazza del Parlamento 1, 90134 Palermo, Italy.), AD(Smithsonian Astrophysical Observatory (SAO), MS 3, 60 Garden Street, Cambridge, MA 02138; .)
Publication:
The Astrophysical Journal, Volume 609, Issue 2, pp. L79-L82. (ApJ Homepage)
Publication Date:
07/2004
Origin:
UCP
ApJ Keywords:
Radiative Transfer, Stars: Coronae, Stars: Late-Type, X-Rays: Stars
Abstract Copyright:
(c) 2004: The American Astronomical Society
DOI:
10.1086/422747
Bibliographic Code:
2004ApJ...609L..79T

Abstract

An analysis of Lyman series lines arising from hydrogen-like oxygen and neon ions in the coronae of the active RS CVn-type binaries II Peg and IM Peg, observed using the Chandra High Resolution Transmission Grating Spectrograph, shows significant decrements in the Lyα/Lyβ ratios as compared with theoretical predictions and with the same ratios observed in similar active binaries. We interpret these decrements in terms of resonance scattering of line photons out of the line of sight; these observations present the first strong evidence of this effect in active stellar coronae. The net line photon loss implies a nonuniform and asymmetric surface distribution of emitting structures on these stars. Escape probability arguments, together with the observed line ratios and estimates of the emitting plasma density, imply typical line-of-sight sizes of the coronal structures that dominate the X-ray emission of 1010 cm at temperatures of 3×106 K and of 108 cm at 107 K. These sizes are an order of magnitude larger than predicted by simple quasi-static coronal loops models but are still very small compared to the several 1011 cm radii of the underlying stars.

Title:
Constraints on Active Region Coronal Heating
Authors:
Antiochos, S. K.; Karpen, J. T.; DeLuca, E. E.; Golub, L.; Hamilton, P.
Affiliation:
AA(E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC 20375; ), AB(E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC 20375; ), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138), AD(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138), AE(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138)
Publication:
The Astrophysical Journal, Volume 590, Issue 1, pp. 547-553. (ApJ Homepage)
Publication Date:
06/2003
Origin:
UCP
ApJ Keywords:
Sun: Corona, Sun: Transition Region, Sun: UV Radiation
Abstract Copyright:
(c) 2003: The American Astronomical Society
DOI:
10.1086/375003
Bibliographic Code:
2003ApJ...590..547A

Abstract

We derive constraints on the time variability of coronal heating from observations of the so-called active region moss by the Transition Region and Coronal Explorer (TRACE). The moss is believed to be due to million-degree emission from the transition regions at the footpoints of coronal loops whose maximum temperatures are several million degrees. The two key results from the TRACE observations discussed in this paper are that in the moss regions one generally sees only moss, not million-degree loops, and that the moss emission exhibits only weak intensity variations, ~10% over periods of hours. TRACE movies showing these results are presented. We demonstrate, using both analytic and numerical calculations, that the lack of observable million-degree loops in the moss regions places severe constraints on the possible time variability of coronal heating in the loops overlying the moss. In particular, the heating in the hot moss loops cannot be truly flarelike with a sharp cutoff, but instead must be quasi-steady to an excellent approximation. Furthermore, the lack of significant variations in the moss intensity implies that the heating magnitude is only weakly varying. The implications of these conclusions for coronal heating models will be discussed.

Title:
Propagating EUV disturbances in the Solar corona: Two-wavelength observations
Authors:
King, D. B.; Nakariakov, V. M.; Deluca, E. E.; Golub, L.; McClements, K. G.
Affiliation:
AA(Physics Department, University of Warwick, Coventry, CV4 7AL, UK ), AB(Physics Department, University of Warwick, Coventry, CV4 7AL, UK ), AC(Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA02138, USA ), AD(Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA02138, USA ), AE(UKAEA Culham Division, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, USA )
Publication:
Astronomy and Astrophysics, v.404, p.L1-L4 (2003) (A&A Homepage)
Publication Date:
06/2003
Origin:
A&A
A&A Keywords:
magnetohydrodynamics (MHD), waves, Sun: activity, Sun: corona, Sun: oscillations, Sun: UV radiation
DOI:
10.1051/0004-6361:20030763
Bibliographic Code:
2003A&A...404L...1K

Abstract

Quasi-periodic EUV disturbances simultaneously observed in 171 Å and 195 Å TRACE bandpasses propagating outwardly in a fan-like magnetic structure of a coronal active region are analysed. Time series of disturbances observed in the different bandpasses have a relatively high correlation coefficient (up to about 0.7). The correlation has a tendency to decrease with distance along the structure: this is consistent with an interpretation of the disturbances in terms of parallel-propagating slow magnetoacoustic waves. The wavelet analysis does not show a significant difference between waves observed in different bandpasses. Periodic patterns of two distinct periods: 2-3 min and 5-8 min are detected in both bandpasses, existing simultaneously and at the same distance along the loop, suggesting the nonlinear generation of the second harmonics.

Title:
The Timing of Flares Associated with the Two Dynamical Types of Solar Coronal Mass Ejections
Authors:
Zhang, M.; Golub, L.; DeLuca, E.; Burkepile, J.
Affiliation:
AA(High Altitude Observatory, National Center for Atmospheric Research, 3450 Mitchell Lane, P.O. Box 3000, Boulder, CO 80307-3000.), AB(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138.), AC(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138.), AD(High Altitude Observatory, National Center for Atmospheric Research, 3450 Mitchell Lane, P.O. Box 3000, Boulder, CO 80307-3000.)
Publication:
The Astrophysical Journal, Volume 574, Issue 1, pp. L97-L100. (ApJ Homepage)
Publication Date:
07/2002
Origin:
UCP
ApJ Keywords:
Magnetohydrodynamics: MHD, Sun: Corona, Sun: Coronal Mass Ejections (CMEs), Sun: Flares
Abstract Copyright:
(c) 2002: The American Astronomical Society
DOI:
10.1086/342275
Bibliographic Code:
2002ApJ...574L..97Z

Abstract

In this Letter, we consider a sample of Transition Region and Coronal Explorer flare-associated solar coronal mass ejections (CMEs) and study the timing behavior of the flares associated with fast or slow CMEs. We find that flares associated with fast CMEs tend to happen within half an hour of the CME onsets, while the timing of flares associated with slow CMEs is only loosely related to the CME onsets. This suggests that the occurrence of flares may be integral to the early development of fast CMEs but is not crucial for slow CMEs. This observational result supports a recent qualitative theory of the initiation and expulsion mechanism of the two dynamical types of CMEs.

Title:
Steady Flows Detected in Extreme-Ultraviolet Loops
Authors:
Winebarger, Amy R.; Warren, Harry; van Ballegooijen, Adriaan; DeLuca, Edward E.; Golub, Leon
Affiliation:
AA(Current address: US Naval Research Laboratory, Code 7673W, Washington, DC 20375; .), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AD(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AE(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , )
Publication:
The Astrophysical Journal, Volume 567, Issue 1, pp. L89-L92. (ApJ Homepage)
Publication Date:
03/2002
Origin:
UCP
ApJ Keywords:
Sun: Corona
Abstract Copyright:
(c) 2002: The American Astronomical Society
DOI:
10.1086/339796
Bibliographic Code:
2002ApJ...567L..89W

Abstract

Recent Transition Region and Coronal Explorer (TRACE) observations have detected a class of active region loops whose physical properties are inconsistent with previous hydrostatic loop models. In this Letter we present the first co-aligned TRACE and the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) observations of these loops. Although these loops appear static in the TRACE images, SUMER detects line-of-sight flows along the loops of up to 40 km s-1. The presence of flows could imply an asymmetric heating function; such a heating function would be expected for heating that is proportional to (often asymmetric) footpoint field strength. We compare a steady flow solution resulting from an asymmetric heating function to a static solution resulting from a uniform heating function in a hypothetical coronal loop. We find that the characteristics associated with the asymmetrically heated loop better compare with the characteristics of the loops observed in the TRACE data.

Title:
Magnetic structure and reconnection of x-ray bright points in the solar corona
Authors:
Brown, D. S.; Parnell, C. E.; Deluca, E. E.; McMullen, R. A.; Golub, L.; Priest, E. R.
Affiliation:
AA(Mathematical Institute, University of St Andrews, St Andrews, KY16 9SS, UK), AB(Mathematical Institute, University of St Andrews, St Andrews, KY16 9SS, UK), AC(Mathematical Institute, University of St Andrews, St Andrews, KY16 9SS, UK), AD(Mathematical Institute, University of St Andrews, St Andrews, KY16 9SS, UK), AE(Mathematical Institute, University of St Andrews, St Andrews, KY16 9SS, UK), AF(Mathematical Institute, University of St Andrews, St Andrews, KY16 9SS, UK)
Publication:
Advances in Space Research, Volume 29, Issue 7, p. 1093-1099. (AdSpR Homepage)
Publication Date:
00/2002
Origin:
ELSEVIER
Abstract Copyright:
(c) 2002 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
2002AdSpR..29.1093B

Abstract

The three-dimensional magnetic topology of the solar corona is incredibly complex and its effect on the nature of 3D reconnection is profound. We study the supposedly simple topology of a small scale X-ray bright point observed by TRACE and SOHO/MDI, and how it is driven by reconnection when it forms and during the early stages of its lifetime.

Title:
Active Region Transient Events Observed with TRACE
Authors:
Seaton, Daniel B.; Winebarger, Amy R.; DeLuca, Edward E.; Golub, Leon; Reeves, Katharine K.; Gallagher, Peter T.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AD(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AE(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; , , , , ), AF(Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314; )
Publication:
The Astrophysical Journal, Volume 563, Issue 2, pp. L173-L177. (ApJ Homepage)
Publication Date:
12/2001
Origin:
UCP
ApJ Keywords:
Sun: Activity, Sun: Corona
Abstract Copyright:
(c) 2001: American Astronomical Society
DOI:
10.1086/338737
Bibliographic Code:
2001ApJ...563L.173S

Abstract

Nearly all active region observations made by the Transition Region and Coronal Explorer (TRACE) contain seemingly spontaneous, short-lived brightenings in small-scale loops. In this paper, we present an analysis of these brightenings using high-cadence TRACE observations of Active Region 9506 on 2001 June 21 from 15:17:00 to 15:46:00 UT. During this time frame, several brightenings were observed over a neutral line in a region of emerging flux that had intensity signatures in both the 171 Å (logTe~6.0) and 1600 Å (logTe~4.0-5.0) channels. The events had a cross-sectional diameter of approximately 2" and a length of 25". We interpret these as reconnection events associated with flux emergence, possible EUV counterparts to active region transient brightenings.

Title:
The Magnetic Structure of a Coronal X-Ray Bright Point
Authors:
Brown, D. S.; Parnell, C. E.; Deluca, E. E.; Golub, L.; McMullen, R. A.
Affiliation:
AA(Institute of Mathematics, University of St Andrews, St Andrews, KY16 9SS, U.K.), AB(Institute of Mathematics, University of St Andrews, St Andrews, KY16 9SS, U.K.), AC(Smithsonian Astrophysical Observatory, Cambridge, MA 02188, U.S.A.), AD(Smithsonian Astrophysical Observatory, Cambridge, MA 02188, U.S.A.), AE(Department of Physics, Montana State University, Bozeman, MT 59717, U.S.A.)
Publication:
Solar Physics, v. 201, Issue 2, p. 305-321 (2001). (SoPh Homepage)
Publication Date:
07/2001
Origin:
KLUWER; SPRINGER
Abstract Copyright:
(c) 2001: Kluwer Academic Publishers
DOI:
10.1023/A:1017907406350
Bibliographic Code:
2001SoPh..201..305B

Abstract

X-ray bright points are small dynamic loop structures that are observed all over the solar corona. The high spatial and temporal resolution of the TRACE instrument allows bright points to be studied in much greater detail than previously possible. This paper focuses on a specific bright point which occurred for about 20 hours on 13 14 June 1998 and examines its dynamic structure in detail. This example suggests that the mechanisms that cause bright points to form and evolve are more complex than previously thought. In this case, reconnection probably plays a major part during the formation and brightening of the loop structure. However, later on the foot points rotate injecting twist into the bright point which may cause an instability to occur with dynamic results.

Title:
A Study of Hydrogen Density in Emerging Flux Loops from a Coordinated Transition Region and Coronal Explorer and Canary Islands Observation Campaign
Authors:
Mein, N.; Schmieder, B.; DeLuca, E. E.; Heinzel, P.; Mein, P.; Malherbe, J. M.; Staiger, J.
Affiliation:
AA(Observatoire de Paris, Section Meudon, 92195 Meudon Principal Cedex, France), AB(Observatoire de Paris, Section Meudon, 92195 Meudon Principal Cedex, France; and Institute of Theoretical Astrophysics, P.O. Box 1029, Blindern, N0315 Oslo, Norway), AC(Smithsonian Astrophysical Observatory, 60 Garden Street, MS 58, Cambridge, MA 02138), AD(Astronomical Institute, Academy of Sciences of the Czech Republic, CZ 25165 Ondřejov, Czech Republic), AE(Observatoire de Paris, Section Meudon, 92195 Meudon Principal Cedex, France), AF(Observatoire de Paris, Section Meudon, 92195 Meudon Principal Cedex, France), AG(Kiepenheuer Institute für Sonnenphysics, D-79104 Freiburg, Germany)
Publication:
The Astrophysical Journal, Volume 556, Issue 1, pp. 438-451. (ApJ Homepage)
Publication Date:
07/2001
Origin:
UCP
ApJ Keywords:
Sun: Activity, Sun: Chromosphere, Sun: Corona, Sun: Magnetic Fields, Sun: UV Radiation
Abstract Copyright:
(c) 2001: The American Astronomical Society
DOI:
10.1086/321488
Bibliographic Code:
2001ApJ...556..438M

Abstract

During an international ground-based campaign in the Canary Islands coordinated with space instruments (i.e., Transition Region and Coronal Explorer [TRACE]), we observed an active region on 1998 September 10 with high spatial and temporal resolution. New emerging flux in the central part of the active region was observed in magnetograms of the Swedish Vacuum Solar Telescope, La Palma. Emerging loops (arch-filament systems [AFSs]) are well developed in Hα and Ca II according to the observations made at the Vacuum Tower Telescope (VTT) and THEMIS telescope in Tenerife with the Multichannel Subtractive Double Pass (MSDP) spectrographs. The TRACE images obtained at 171 and 195 Å show low-emission regions that are easily identified as the individual AFS. They are due to absorption by hydrogen and helium continua in the cool filament plasma. We compare two techniques of measuring the hydrogen density in the cool dense fibrils of AFSs. The first method based on TRACE observations derived the neutral hydrogen column density of the plasma absorbing coronal lines. The second one using Hα line profiles provided by the MSDP spectrographs is based on the cloud model. The results are consistent. We derive also electron density values using Hα lines that are in good agreement with those derived from the 8542 Å Ca II line observed with THEMIS (Mein et al.). The three types of observations (TRACE, VTT, THEMIS) are well complementary: absorption of coronal lines giving a good approximation for the maximum value of the neutral hydrogen column density, the Hα line giving a good determination of ne, and the 8542 Å Ca II line a good determination of the electronic temperature.

Title:
Apparent Flows above an Active Region Observed with the Transition Region and Coronal Explorer
Authors:
Winebarger, Amy R.; DeLuca, Edward E.; Golub, Leon
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 58, Cambridge, MA 02138; , , ), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 58, Cambridge, MA 02138; , , ), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 58, Cambridge, MA 02138; , , )
Publication:
The Astrophysical Journal, Volume 553, Issue 1, pp. L81-L84. (ApJ Homepage)
Publication Date:
05/2001
Origin:
UCP
ApJ Keywords:
Sun: Activity, Sun: Corona
Abstract Copyright:
(c) 2001: The American Astronomical Society
DOI:
10.1086/320496
Bibliographic Code:
2001ApJ...553L..81W

Abstract

The Transition Region and Coronal Explorer (TRACE) observed Active Region 8395 on 1998 December 1 from 1:30:00 to 3:00:00 UT at high cadence in the Fe IX/Fe X channel (logTe~6.0). Throughout the observing time, brightness variations along a dense bundle of coronal field lines in the southwest corner of the active region were observed. Movies made of this region give the impression of continuous intermittent outflow in this bundle of coronal loops; such apparent outflow is often seen in the TRACE data. In this Letter, we present an analysis of four separate flow events occurring in three different loops. These events are used as tracers of the flow in order to characterize its physical properties, such as apparent velocity. The projected velocities of the intensity fronts of these flows (and hence lower limits of true velocities) are between 5 and 20 km s-1. Comparisons of the observed intensities with those predicted by a quasi-static model suggest that the events can be explained only by a mass flow from the chromosphere into the corona. The persistence of the flows, and their ubiquity in the TRACE observations, indicates that hydrostatic loops models are not applicable to this class of coronal structures.

Title:
Magnetic Diffusion in Stratified Atmospheres
Authors:
DeLuca, E. E.; Hurlburt, N. E.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Smithsonian Astrophysical Observatory, 60 Garden Street, MS 58, Cambridge, MA 02138), AB(Lockheed Martin Advanced Technology Center, Organization L9-41 Building 252, Palo Alto, CA 94304)
Publication:
The Astrophysical Journal, Volume 548, Issue 2, pp. 1093-1101. (ApJ Homepage)
Publication Date:
02/2001
Origin:
UCP
ApJ Keywords:
Convection, Magnetohydrodynamics: MHD, Stars: Interiors, Sun: Magnetic Fields
Abstract Copyright:
(c) 2001: The American Astronomical Society
DOI:
10.1086/318995
Bibliographic Code:
2001ApJ...548.1093D

Abstract

The predictions from mean field electrodynamics have been questioned because of the strong feedback of small-scale magnetic structure on the velocity fields. In two dimensions, this nonlinear feedback results in a lengthening of the turbulent decay time. In three dimensions α-quenching is predicted. Previous studies assumed a homogeneous fluid. We will present recent results from two-dimensional compressible MHD decay simulations in a highly stratified atmosphere that more closely resembles the solar convection zone. Our results show that the field geometry has a strong influence on the decay rate: vertical fields remain fairly constant for a period of time and then rapidly decay on the turbulent timescale; horizontal fields decay at an intermediate rate with strong fields persisting near the top and bottom boundaries. The implication of our results for understanding solar active region decay is discussed.

Title:
Determination of Flare Heating and Cooling Using the Transition Region and Coronal Explorer
Authors:
Antiochos, S. K.; DeLuca, E. E.; Golub, L.; McMullen, R. A.
Affiliation:
AA(E. O. Hulburt Center for Space Research, US Naval Research Laboratory, Washington, DC, 20375; ), AB(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138), AC(Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138), AD(Department of Physics, Montana State University, EPS 264B, P.O. Box 173840, Bozeman, MT 59717-3840)
Publication:
The Astrophysical Journal, Volume 542, Issue 2, pp. L151-L154. (ApJ Homepage)
Publication Date:
10/2000
Origin:
UCP
ApJ Keywords:
Sun: Flares, Sun: Transition Region, Sun: X-Rays, Gamma Rays
Abstract Copyright:
(c) 2000: The American Astronomical Society
DOI:
10.1086/312927
Bibliographic Code:
2000ApJ...542L.151A

Abstract

We describe how the Transition Region and Coronal Explorer 171 Å observations can be used to determine the properties of flare-loop heating. The key point is that the evolution of a loop transition region (TR) is much easier to measure quantitatively than the bulk flare plasma because the TR emission originates from an unobscured source with simple geometry. We derive general analytic expressions for the evolution of a flare-loop TR that, in principle, permit a determination of the heating function from the observations. These results are compared with observations of the 1998 September 20 flare. We find that the observed evolution of the flare ribbons is in good agreement with our model for the evaporative cooling of flare loops and that the heating in these loops is incompatible with the assumption of spatial uniformity.

Title:
The Topology and Evolution of the Bastille Day Flare
Authors:
Aulanier, G.; DeLuca, E. E.; Antiochos, S. K.; McMullen, R. A.; Golub, L.
Affiliation:
AA(Postal address: Naval Research Laboratory, Code 7670, Washington, DC 20375), AB(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138), AC(Postal address: Naval Research Laboratory, Code 7670, Washington, DC 20375), AD(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138), AE(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138)
Publication:
The Astrophysical Journal, Volume 540, Issue 2, pp. 1126-1142. (ApJ Homepage)
Publication Date:
09/2000
Origin:
UCP
ApJ Keywords:
Magnetohydrodynamics: MHD, Sun: Flares, Sun: Magnetic Fields, Sun: UV Radiation
Abstract Copyright:
(c) 2000: The American Astronomical Society
DOI:
10.1086/309376
Bibliographic Code:
2000ApJ...540.1126A

Abstract

On 1998 July 14, a class M3 flare occurred at 12:55 UT in AR 8270 near disk center. Kitt Peak line-of-sight magnetograms show that the flare occurred in a δ spot. Mees vector magnetograms show a strong shear localized near a portion of the closed neutral line around the parasitic polarity of the δ spot. Observations of the flare in 171, 195, and 1600 Å have been obtained by TRACE, with ~=40 s temporal and 0.5" spatial resolutions. They reveal that small-scale preflare loops above the sheared region expanded and disappeared for more than 1 hr before flare maximum. During the flare, bright loops anchored in bright ribbons form and grow. This occurs while large-scale dimmings, associated with large expanding loops, develop on both sides of the active region. This suggests that the flare was eruptive and was accompanied by a coronal mass ejection (CME). Magnetic field extrapolations reveal the presence of a null point in the corona, with its associated ``spine'' field line, and its ``fan'' surface surrounding the parasitic polarity. We show that while the whole event occurs, the intersections of the ``fan'' and the ``spine'' with the photosphere brighten and move continuously. The interpretation of the event shows that the magnetic evolution of the eruptive flare is strongly coupled with its surrounding complex topology. We discuss evidence supporting a ``magnetic breakout'' process for triggering this eruptive flare. We finally conclude that multipolar fields cannot be neglected in the study and modeling of the origin of CMEs in the corona.

Title:
Emergence of sheared magnetic flux tubes in an active region observed with the SVST and TRACE
Authors:
Deng, Y. Y.; Schmieder, B.; Engvold, O.; DeLuca, E.; Golub, L.
Affiliation:
AA(Beijing Astronomical Observatory, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China), AB(Observatoire de Paris, Section de Meudon, 92195 Meudon Principal Cedex, France), AC(Institute of Astrophysics, University of Oslo, Blindern, Norway), AD(Smithsonian Astrophysical Observatory, 60 Garden Street MS 58, Cambridge, MA 02138, U.S.A.), AE(Smithsonian Astrophysical Observatory, 60 Garden Street MS 58, Cambridge, MA 02138, U.S.A.)
Publication:
Solar Physics, v. 195, Issue 2, p. 347-366 (2000). (SoPh Homepage)
Publication Date:
08/2000
Origin:
KLUWER
Abstract Copyright:
(c) 2000 Kluwer Academic Publishers
Bibliographic Code:
2000SoPh..195..347D

Abstract

The active region NOAA AR 8331 was a target of an international ground-based observational campaign in the Canaries and coordinated with space instruments (TRACE and Yohkoh). We focus our study on observations obtained with the SVST at LaPalma, and with TRACE. On 10 September 1998, arch-filament systems were observed with high spatial and temporal resolution, from the lower to the upper atmosphere of the Sun, during five hours. Flux tubes emerged with increasing shear, which apparently led to energy release and heating in the overlying corona. A model for filament formation by the emergence of U-shaped loops from the subphotosphere, as proposed by Rust and Kumar (1994), is supported by the present observations. The coronal response to these events is visualized by rising, medium-scale loop brightenings. The low-lying X-ray loops show short-lived, bright knots which are thought to result from interaction between different loop systems.

Title:
A Brightening Coronal Loop Observed by TRACE. II. Loop Modeling and Constraints on Heating
Authors:
Reale, F.; Peres, G.; Serio, S.; Betta, R. M.; DeLuca, E. E.; Golub, L.
Affiliation:
AA(Osservatorio Astronomico, Piazza del Parlamento 1, I-90134, Palermo, Italy), AB(Osservatorio Astronomico, Piazza del Parlamento 1, I-90134, Palermo, Italy), AC(Osservatorio Astronomico, Piazza del Parlamento 1, I-90134, Palermo, Italy), AD(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy), AE(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138), AF(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138)
Publication:
The Astrophysical Journal, Volume 535, Issue 1, pp. 423-437. (ApJ Homepage)
Publication Date:
05/2000
Origin:
UCP
ApJ Keywords:
Sun: Activity, Sun: Corona, Sun: X-Rays, Gamma Rays
Abstract Copyright:
(c) 2000: The American Astronomical Society
DOI:
10.1086/308817
Bibliographic Code:
2000ApJ...535..423R

Abstract

This is the second of two papers dedicated to the brightening of a coronal loop observed by the Transition Region and Coronal Explorer (TRACE) on 1998 June 26; it aims at hydrodynamic modeling of the brightening. Since the loop geometry is practically unchanged during the brightening, the evolution of the plasma confined in the loop is described with a one-dimensional hydrodynamic time-dependent numerical model, and from the results the emission along the loop in the TRACE 171 Å band is synthesized. The information from Paper I is used to derive the geometry and the initial configuration of the loop as well as for comparison with the results of the model. The modeling is focused to determine the amount, spatial distribution, and evolution of the heating deposited in the loop to make the modeled evolution close to that observed with TRACE. We find that, in order to match the observed evolution and distribution of the brightness along the loop, the heating has to be nonsymmetrical in the loop, in particular, deposited between the apex and one footpoint (3×109 cm from the southern footpoint). A reasonable match with observations is obtained by assuming that the heating is switched on abruptly and then kept constant for the whole rising phase. An even better match is obtained with the heating high and constant for 100 s and then decaying exponentially with an e-folding time of 300 s. We discuss the resulting physical scenario; a bright irregular structure close to the loop in the TRACE images may be a tracer of the heating release.

Title:
A Brightening Coronal Loop Observed by TRACE. I. Morphology and Evolution
Authors:
Reale, F.; Peres, G.; Serio, S.; DeLuca, E. E.; Golub, L.
Affiliation:
AA(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy), AB(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy), AC(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy), AD(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138), AE(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138)
Publication:
The Astrophysical Journal, Volume 535, Issue 1, pp. 412-422. (ApJ Homepage)
Publication Date:
05/2000
Origin:
UCP
ApJ Keywords:
Sun: Activity, Sun: Corona, Sun: X-Rays, Gamma Rays
Abstract Copyright:
(c) 2000: The American Astronomical Society
DOI:
10.1086/308816
Bibliographic Code:
2000ApJ...535..412R

Abstract

We analyze the transient brightening of a solar coronal loop observed, at high time cadence (30 s) and spatial resolution (0.5" pixel size), with the Transition Region and Coronal Explorer (TRACE) in the 171 Å band on 1998 June 26. The loop, located in AR 8253, is ~1010 cm long and inclined with respect to the vertical to the solar surface. Its geometry and shape do not change significantly during the brightening, which lasts for ~2 hr and is preceded by highly dynamic events in nearby and perhaps interacting loops. The loop footpoints brighten first; after ~10 minutes, moving brightness fronts rise initially from the northern footpoint, and after another ~7 minutes from the southern one, at an apparent speed ~100 km s-1, the whole loop becoming clearly visible afterward. During the rising phase the loop evolves coherently as a single magnetic tube. The brightness profile is asymmetric with respect to the loop apex at all times; the brightness contrast between the footpoints and the apex decreases with time from a ratio of ~10 to ~3. After the loop has become all visible, the several parallel filaments which form it follow an independent evolution. Assuming a plasma temperature of ~1 MK, we infer a plasma density of ~6×108 cm -3 and a pressure of ~0.2 dyn cm-2 close to the loop apex at the luminosity maximum. A companion paper is devoted to modeling the rising phase of this event.

Title:
Long-lived Coronal Loop Profiles from TRACE
Authors:
Lenz, Dawn D.; Deluca, Edward E.; Golub, Leon; Rosner, Robert; Bookbinder, Jay A.; Litwin, Christof; Reale, Fabio; Peres, Giovanni
Affiliation:
AA(Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, U.S.A., ), AB(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, U.S.A.), AC(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, U.S.A.), AD(Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, U.S.A., ), AE(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, U.S.A., ), AF(Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, U.S.A., ), AG(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, I-90134, Palermo, Italy, ), AH(Dipartimento di Scienze Fisiche e Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, I-90134, Palermo, Italy)
Publication:
Solar Physics, v. 190, Issue 1/2, p. 131-138 (1999). (SoPh Homepage)
Publication Date:
12/1999
Origin:
KLUWER; SPRINGER
Abstract Copyright:
(c) 1999: Kluwer Academic Publishers
DOI:
10.1023/A:1005209616355
Bibliographic Code:
1999SoPh..190..131L

Abstract

An initial study of long-lived loops observed with TRACE (Lenz et al., 1999) shows that they have no significant temperature stratification and that they are denser than the classic loop model predicts. Models that agree better with the observations include a loop consisting of a bundle of filaments at different temperatures and a loop with momentum input by MHD waves. Some implications for coronal heating models and mechanisms are discussed.

Title:
TRACE observation of damped coronal loop oscillations: Implications for coronal heating
Authors:
Nakariakov, V. M.; Ofman, L.; Deluca, E. E.; Roberts, B.; Davila, J. M.
Publication:
Science, Vol. 285, Iss. 5429, pp. 862-864 (1999)
Publication Date:
08/1999
Origin:
AUTHOR
Bibliographic Code:
1999Sci...285..862N

Abstract

Not Available

Title:
A new view of the solar outer atmosphere by the Transition Region and Coronal Explorer
Authors:
Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.; Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.; Wolfson, J.; Golub, L.; Bookbinder, J. A.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; de Pontieu, B.
Affiliation:
AA(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AB(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AC(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AD(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AE(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AF(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AG(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AH(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AI(Stanford-Lockheed Institute for Space Research, Dept. H1-12, Bldg. 252, 3251 Hanover Street, Palo Alto CA 94304, U.S.A.), AJ(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge MA 02138, U.S.A.), AK(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge MA 02138, U.S.A.), AL(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge MA 02138, U.S.A.), AM(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge MA 02138, U.S.A.), AN(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge MA 02138, U.S.A.), AO(Department of Physics, Montana State University-Bozeman, P.O. Box 173840, Bozeman, Montana 59717, U.S.A.), AP(Department of Physics, Montana State University-Bozeman, P.O. Box 173840, Bozeman, Montana 59717, U.S.A.), AQ(Max Planck Institut für Extraterrestrische Physik, D-85740 Garching bei München, Germany)
Publication:
Solar Physics, v. 187, Issue 2, p. 261-302 (1999). (SoPh Homepage)
Publication Date:
07/1999
Origin:
KLUWER; SPRINGER
Abstract Copyright:
(c) 1999: Kluwer Academic Publishers
DOI:
10.1023/A:1005194519642
Bibliographic Code:
1999SoPh..187..261S

Abstract

The Transition Region and Coronal Explorer (TRACE) described in the companion paper by Handy et al. (1999) provides an unprecedented view of the solar outer atmosphere. In this overview, we discuss the initial impressions gained from, and interpretations of, the first million images taken with TRACE. We address, among other topics, the fine structure of the corona, the larger-scale thermal trends, the evolution of the corona over quiet and active regions, the high incidence of chromospheric material dynamically embedded in the coronal environment, the dynamics and structure of the conductively dominated transition region between chromosphere and corona, loop oscillations and flows, and sunspot coronal loops. With TRACE we observe a corona that is extremely dynamic and full of flows and wave phenomena, in which loops evolve rapidly in temperature, with associated changes in density. This dynamic nature points to a high degree of spatio-temporal variability even under conditions that traditionally have been referred to as quiescent. This variability requires that coronal heating can turn on and off on a time scale of minutes or less along field-line bundles with cross sections at or below the instrumental resolution of 700 km. Loops seen at 171 Å (˜1 MK) appear to meander through the coronal volume, but it is unclear whether this is caused by the evolution of the field or by the weaving of the heating through the coronal volume, shifting around for periods of up to a few tens of minutes and lighting up subsequent field lines. We discuss evidence that the heating occurs predominantly within the first 10 to 20 Mm from the loop footpoints. This causes the inner parts of active-region coronae to have a higher average temperature than the outer domains.

Title:
The transition region and coronal explorer
Authors:
Handy, B. N.; Acton, L. W.; Kankelborg, C. C.; Wolfson, C. J.; Akin, D. J.; Bruner, M. E.; Caravalho, R.; Catura, R. C.; Chevalier, R.; Duncan, D. W.; Edwards, C. G.; Feinstein, C. N.; Freeland, S. L.; Friedlaender, F. M.; Hoffmann, C. H.; Hurlburt, N. E.; Jurcevich, B. K.; Katz, N. L.; Kelly, G. A.; Lemen, J. R.; Levay, M.; Lindgren, R. W.; Mathur, D. P.; Meyer, S. B.; Morrison, S. J.; Morrison, M. D.; Nightingale, R. W.; Pope, T. P.; Rehse, R. A.; Schrijver, C. J.; Shine, R. A.; Shing, L.; Strong, K. T.; Tarbell, T. D.; Title, A. M.; Torgerson, D. D.; Golub, L.; Bookbinder, J. A.; Caldwell, D.; Cheimets, P. N.; Davis, W. N.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.; Amato, D.; Fisher, R.; Maldonado, H.; Parkinson, C.
Affiliation:
AA(Department of Physics, Montana State University-Bozeman, P.O. Box 173840, Bozeman, Montana 59717, U.S.A.), AB(Department of Physics, Montana State University-Bozeman, P.O. Box 173840, Bozeman, Montana 59717, U.S.A.), AC(Department of Physics, Montana State University-Bozeman, P.O. Box 173840, Bozeman, Montana 59717, U.S.A.), AD(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AE(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AF(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AG(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AH(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AI(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AJ(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AK(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AL(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AM(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AN(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AO(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AP(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AQ(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AR(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AS(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AT(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AU(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AV(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AW(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AX(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AY(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), AZ(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BA(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BB(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BC(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BD(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BE(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BF(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BG(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BH(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BI(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BJ(Lockheed Martin Palo Alto Advanced Technology Center, O/L9-41, B-252, 3251 Hanover Street, Palo Alto, California 94304, U.S.A.), BK(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BL(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BM(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BN(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BO(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BP(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BQ(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BR(Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, U.S.A.), BS(NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A.), BT(NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A.), BU(NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A.), BV(NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A.)
Publication:
Solar Physics, v. 187, Issue 2, p. 229-260 (1999). (SoPh Homepage)
Publication Date:
07/1999
Origin:
KLUWER; SPRINGER
Abstract Copyright:
(c) 1999: Kluwer Academic Publishers
DOI:
10.1023/A:1005166902804
Bibliographic Code:
1999SoPh..187..229H

Abstract

The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The ˜700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min.

Title:
Temperature and Emission-Measure Profiles along Long-lived Solar Coronal Loops Observed with the Transition Region and Coronal Explorer
Authors:
Lenz, Dawn D.; Deluca, Edward E.; Golub, Leon; Rosner, Robert; Bookbinder, Jay A.
Publication:
The Astrophysical Journal, Volume 517, Issue 2, pp. L155-L158. (ApJ Homepage)
Publication Date:
06/1999
Origin:
APJ
ApJ Keywords:
SUN: CORONA, SUN: UV RADIATION
Abstract Copyright:
(c) 1999: The American Astronomical Society
DOI:
10.1086/312045
Bibliographic Code:
1999ApJ...517L.155L

Abstract

We report an initial study of temperature and emission-measure distributions along four steady loops observed with the Transition Region and Coronal Explorer at the limb of the Sun. The temperature diagnostic is the filter ratio of the extreme-ultraviolet 171 and 195 Å passbands. The emission-measure diagnostic is the count rate in the 171 Å passband. We find essentially no temperature variation along the loops. We compare the observed loop structure with theoretical isothermal and nonisothermal static loop structure.

Title:
A new view of the solar corona from the Transition Region and Coronal Explorer (TRACE).
Authors:
Golub, L.; Bookbinder, J.; Deluca, E.; Karovska, M.; Warren, H.; Schrijver, C. J.; Shine, R.; Tarbell, T.; Title, A.; Wolfson, J.; Handy, B.; Kankelborg, C.
Publication:
Phys. Plasmas, Vol. 6, No. 5, p. 2205 - 2216 (PhPl Homepage)
Publication Date:
05/1999
Origin:
ARI
Keywords:
Solar Corona: Filaments, Solar Corona: Structure, Solar Corona: Space Missions
Bibliographic Code:
1999PhPl....6.2205G

Abstract

The TRACE Observatory is the first solar-observing satellite in NASA's Small Explorer series. Launched April 2, 1998, it is providing views of the solar transition region and low corona with unprecedented spatial and temporal resolution. The corona is now seen to be highly filamented, and filled with flows and other dynamic processes. Structure is seen down to the resolution limit of the instrument, while variability and motions are observed at all spatial locations in the solar atmosphere, and on very short time scales. Flares and shock waves are observed, and the formation of long-lived coronal structures, with consequent implications for coronal heating models, has been seen. This overview describes the instrument and presents some preliminary results from the first six months of operation.

Title:
Magnetohydrodynamic Turbulence of Coronal Active Regions and the Distribution of Nanoflares
Authors:
Dmitruk, Pablo; Gómez, Daniel O.; Deluca, Edward E.
Publication:
The Astrophysical Journal, Volume 505, Issue 2, pp. 974-983. (ApJ Homepage)
Publication Date:
10/1998
Origin:
APJ
ApJ Keywords:
MAGNETOHYDRODYNAMICS: MHD, SUN: CORONA, SUN: FLARES, TURBULENCE
Abstract Copyright:
(c) 1998: The American Astronomical Society
DOI:
10.1086/306182
Bibliographic Code:
1998ApJ...505..974D

Abstract

We present results from numerical simulations of an externally driven two-dimensional magnetohydrodynamic system over extended periods of time, used to model the dynamics of a transverse section of a solar coronal loop. A stationary forcing was imposed to model the photospheric motions at the loop footpoints. After several photospheric turnover times, a turbulent stationary regime is reached that has an energy dissipation rate consistent with the heating requirements of coronal loops. The turbulent velocities obtained in our simulations are consistent with those derived from the nonthermal broadening of coronal spectral lines. We also show the development of small scales in the spatial distribution of electric currents, which are responsible for most of the energy dissipation. The energy dissipation rate as a function of time displays an intermittent behavior, in the form of impulsive events, that is a direct consequence of the strong nonlinearity of the system. We associate these impulsive events of magnetic energy dissipation with the so-called nanoflares. A statistical analysis of these events yields a power-law distribution as a function of their energies with a negative slope of 1.5, consistent with those obtained for flare energy distributions reported from X-ray observations. A simple model of dissipative structures, based on Kraichnan's theory for MHD turbulence, is also presented.

Title:
The Emergence of Magnetic Flux Loops in Sunlike Stars
Authors:
Deluca, Edward E.; Fan, Yuhong; Saar, Steven H.
Publication:
Astrophysical Journal v.481, p.369 (ApJ Homepage)
Publication Date:
05/1997
Origin:
APJ
ApJ Keywords:
MAGNETOHYDRODYNAMICS: MHD, STARS: ACTIVITY, STARS: MAGNETIC FIELDS, STARS: ROTATION
Abstract Copyright:
(c) 1997: The American Astronomical Society
DOI:
10.1086/304038
Bibliographic Code:
1997ApJ...481..369D

Abstract

We explore the latitude of emergence of flux tubes at the surface of G stars as a function of the rotation rate, magnetic flux, and injection latitude at the bottom of the convective zone. Our analysis is based on a thin flux tube evolution code that has been developed to study the emergence of magnetic flux in the Sun and is well calibrated by detailed comparisons with solar observations. We study solar models with rotation rates between \frac {1}{3} and 10 times solar, injection latitudes phi I between 1 deg and 40 deg, and tubes with a range of field strengths, B0, and fluxes. For our range of input parameters, we find that the mean latitude of emergence, < phi E>, increases and its range decreases with higher rotation rates, that phi E <= 45 deg for stars with rotational periods >=27 days, that phi E increases with B0 in rapid rotators, while the reverse is true for slow rotators, that the dependence of phi E on B0 decreases with increasing phi I, that tubes with higher flux emerge at larger phi E, and that the footpoint separation depends linearly on B0. We compare our results to other calculations and with observations of magnetic features on stars and suggest future observations and extensions of this research. Our results suggest that for near-polar starspots to occur, either active stars must have a larger range of phi I than inferred for the Sun, or differential rotation and meridional flows are more important for magnetic flux redistribution in these stars. Our models also imply that flux appearing near the equator of active stars may be generated by a distributed, rather than a boundary layer, dynamo.

Title:
Observations and Interpretation of Soft X-Ray Limb Absorption Seen by the Normal Incidence X-Ray Telescope
Authors:
Daw, A.; Deluca, E. E.; Golub, L.
Publication:
Astrophysical Journal v.453, p.929 (ApJ Homepage)
Publication Date:
11/1995
Origin:
APJ; KNUDSEN
ApJ Keywords:
SUN: CHROMOSPHERE, SUN: X-RAYS
DOI:
10.1086/176453
Bibliographic Code:
1995ApJ...453..929D

Abstract



Title:
Nonlinear Energy Transfer in Solar Magnetic Loops
Authors:
Gomez, Daniel O.; Deluca, Edward E.; McClymont, Alexander N.
Publication:
Astrophysical Journal v.448, p.954 (ApJ Homepage)
Publication Date:
08/1995
Origin:
APJ; KNUDSEN
ApJ Keywords:
INSTABILITIES, MAGNETOHYDRODYNAMICS: MHD, SUN: CORONA, SUN: MAGNETIC FIELDS
DOI:
10.1086/176024
Bibliographic Code:
1995ApJ...448..954G

Abstract



Title:
The dynamics of magnetic flux rings
Authors:
Deluca, E. E.; Fisher, G. H.; Patten, B. M.
Affiliation:
AA(Hawaii Univ., Honolulu), AB(California Univ., Berkeley), AC(Hawaii Univ., Honolulu)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 411, no. 1, p. 383-393. (ApJ Homepage)
Publication Date:
07/1993
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
CONVECTION, DYNAMICS, MAGNETIC FLUX, MAGNETOHYDRODYNAMIC TURBULENCE, SOLAR CYCLES, SOLAR MAGNETIC FIELD, DYNAMO THEORY, FLOW DISTRIBUTION, SOLAR ATMOSPHERE, SOLAR PHYSICS
DOI:
10.1086/172839
Bibliographic Code:
1993ApJ...411..383D

Abstract

The evolution of magnetic fields in the presence of turbulent convection is examined using results of numerical simulations of closed magnetic flux tubes embedded in a steady 'ABC' flow field, which approximate some of the important characteristics of a turbulent convecting flow field. Three different evolutionary scenarios were found: expansion to a steady deformed ring; collapse to a compact fat flux ring, separated from the expansion type of behavior by a critical length scale; and, occasionally, evolution toward an advecting, oscillatory state. The work suggests that small-scale flows will not have a strong effect on large-scale, strong fields.

Title:
The origin of morphological asymmetries in bipolar active regions
Authors:
Fan, Y.; Fisher, G. H.; Deluca, E. E.
Affiliation:
AA(Hawaii Univ., Honolulu), AB(Hawaii Univ., Honolulu; California Univ., Berkeley), AC(Hawaii Univ., Honolulu)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 405, no. 1, p. 390-401. (ApJ Homepage)
Publication Date:
03/1993
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
SOLAR ACTIVITY, SOLAR MAGNETIC FIELD, SOLAR PHYSICS, CORIOLIS EFFECT, MATHEMATICAL MODELS, SOLAR INTERIOR, SUNSPOTS
DOI:
10.1086/172370
Bibliographic Code:
1993ApJ...405..390F

Abstract

A series of 3D numerical simulations was carried out to examine the dynamical evolution of emerging flux loops in the solar convective envelope. The innermost portions of the loops are anchored beneath the base of the convective zone by the subadiabatic temperature gradient of the underlying overshoot region. It is found that, as the emerging loops approach the photosphere, the magnetic field strength of the leading side of each rising loop is about twice as large as that of the following side at the same depth. The evacuation of plasma out of the leading side of the rising loop results in an enhanced magnetic field strength there compared with the following side. It is argued that this result provides a natural explanation for the fact that the preceding (leading) polarity tends to have a less organized and more fragmented appearance, and that the preceding spots tend to be larger in area and fewer in number, and have a longer lifetime than the following spots.

Title:
Magnetic reconnection in incompressible fluids
Authors:
Deluca, Edward E.; Craig, Ian J.
Affiliation:
AA(Hawaii, University, Honolulu), AB(Waikato, University, Hamilton, New Zealand)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 390, no. 2, May 10, 1992, p. 679-686. (ApJ Homepage)
Publication Date:
05/1992
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
INCOMPRESSIBLE FLUIDS, MAGNETIC FIELD RECONNECTION, MAGNETOHYDRODYNAMICS, SOLAR FLARES, SOLAR MAGNETIC FIELD, CURRENT SHEETS, ENERGY DISSIPATION, MAGNETIC FLUX, SCALING LAWS, SOLAR ATMOSPHERE, SOLAR PHYSICS
DOI:
10.1086/171319
Bibliographic Code:
1992ApJ...390..679D

Abstract

The paper investigates the dynamical relaxation of a disturbed X-type magnetic neutral point in a periodic geometry, with an ignorable coordinate, for an incompressible fluid. It is found that the properties of the current sheet cannot be understood in terms of steady state reconnection theory or more recent linear dynamical solutions. Accordingly, a new scaling law for magnetic reconnection is presented, consistent with fast energy dissipation (i.e., the dissipation rate at current maximum is approximately independent of magnetic diffusivity (eta)). The flux annihilation rate, however, scales at eta exp 1/4, faster than the Sweet-Parker rate of sq rt eta but asymptotically much slower than the dissipation rate. These results suggest a flux pile-up regime in which the bulk of the free magnetic energy is released as heat rather than as kinetic energy of mass motion. The implications of our results for reconnection in the solar atmosphere and interior are discussed.

Title:
Development of hard-turbulent convection in two dimensions: Numerical evidence
Authors:
Werne, J.; Deluca, E. E.; Rosner, R.; Cattaneo, F.
Publication:
Physical Review Letters, Volume 67, Issue 25, December 16, 1991, pp.3519-3522 (PhRvL Homepage)
Publication Date:
12/1991
Origin:
AIP
Bibliographic Code:
1991PhRvL..67.3519W

Abstract

Not Available

Title:
Numerical simulations of soft and hard turbulence: Preliminary results for two-dimensional convection
Authors:
Deluca, E. E.; Werne, J.; Rosner, R.; Cattaneo, F.
Publication:
Physical Review Letters, Volume 64, Issue 20, May 14, 1990, pp.2370-2373 (PhRvL Homepage)
Publication Date:
05/1990
Origin:
AIP
Bibliographic Code:
1990PhRvL..64.2370D

Abstract

Not Available

Title:
Angular momentum transport and dynamo action in the sun - Implications of recent oscillation measurements
Authors:
Gilman, Peter A.; Morrow, Cherilynn A.; Deluca, Edward E.
Affiliation:
AA(High Altitude Observatory, Boulder, CO), AB(High Altitude Observatory, Boulder, CO), AC(High Altitude Observatory, Boulder, CO)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 338, March 1, 1989, p. 528-537. (ApJ Homepage)
Publication Date:
03/1989
Category:
Solar Physics
Origin:
STI
NASA/STI Keywords:
ANGULAR MOMENTUM, DYNAMO THEORY, MAGNETOHYDRODYNAMICS, SOLAR INTERIOR, SOLAR OSCILLATIONS, SOLAR ROTATION, MOMENTUM TRANSFER, SOLAR VELOCITY
DOI:
10.1086/167215
Bibliographic Code:
1989ApJ...338..528G

Abstract

The implications of a newly proposed picture of the sun's internal rotation (Brown et al., 1989; Morrow, 1988) for the distribution and transport of angular momentum and for the solar dynamo are considered. The new results, derived from an analysis of solar acoustic oscillations, affect understanding of how momentum is cycled in the sun and provide clues as to how and where the solar dynamo is driven. The data imply that the only significant radial gradient of angular velocity exists in a transitional region between the bottom of the convection zone, which is rotating like the solar surface, and the top of the deep interior, which is rotating rigidly at a rate intermediate between the equatorial and polar rates at the surface. Thus the radial gradient must change sign at the latitude where the angular velocity of the surface matches that of the interior. These inferences suggest that the cycle of angular momentum that produces the observed latitudinal differential rotation in the convection zone may be coupled to layers of the interior beneath the convection zone.

Title:
Dynamo theory for the interface between the convection zone and the radiative interior of a star. 2. Numerical solutions of the nonlinear equations.
Authors:
Deluca, E. E.; Gilman, P. A.
Publication:
Geophys. Astrophys. Fluid Dyn., Vol. 43, No. 2, p. 119 - 148
Publication Date:
12/1988
Origin:
ARI
Keywords:
Dynamo Theory: Stellar Interiors, Dynamo Theory: Convective Zones, Dynamo Theory: Sun
Bibliographic Code:
1988GApFD..43..119D

Abstract

The authors discuss numerical solutions of nonlinear equations that model magnetic field generation in a thin layer beneath the convection zone of a late type star. The model equations were derived previously in Paper I (DeLuca and Gilman, 1986, 43.062.160). Three main results are found: first, the oscillating, dynamo wave solutions discussed in DeLuca and Gilman (1986) are shown to be a result of the severe truncation used in those calculations; second, the induced velocity field is shown to have an important role in determining the spatial structure of the magnetic field solutions; time dependent solutions have been found. Further, the authors show that the exact solutions found in Paper I are generally unstable. They conclude that the induced velocity fields are an important ingredient in any model of dynamo action below the solar convection zone.

Title:
Dynamo Theory for the Interface Between the Convection Zone and the Radiative Interior of a Star. I. Model Equations and Exact Solutions
Authors:
Deluca, E. E.; Gilman, P. A.
Publication:
Geophys. Astrophys. Fluid Dynamics, Volume 37, p. 85-127
Publication Date:
10/1986
Origin:
GONG
Keywords:
DYNAMO THEORY, MAGNETIC FIELDS, THEORY, CONVECTION, ROTATION,
Bibliographic Code:
1986GApFD..37...85D

Abstract

Not Available

Title:
Dynamo Theory for a Thin Layer Between the Convection Zone and the Radiative Zone of a Star. Formulation and Preliminary Results
Authors:
Deluca, E. E.; Gilman, P. A.
Publication:
Cool Stars, Stellar Systems and the Sun, Proceedings of the Fourth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Held in Santa Fe, New Mexico, October 16-18, 1985. Lecture Notes in Physics, Vol. 254, edited by Michael Zeilik and David M. Gibson, Springer-Verlag, Berlin Heidelberg New York, 1986., p.173
Publication Date:
00/1986
Origin:
ADS
Bibliographic Code:
1986LNP...254..173D

Abstract

The authors present a dynamo model for the overshoot region between the convection zone and the radiative zone of a late type star. They show how the model equations are derived and discuss some of the solutions of those equations.

Title:
Dynamo Theory for the Sun and Stars
Authors:
Gilman, P. A.; Deluca, E. E.
Publication:
Cool Stars, Stellar Systems and the Sun, Proceedings of the Fourth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Held in Santa Fe, New Mexico, October 16-18, 1985. Lecture Notes in Physics, Vol. 254, edited by Michael Zeilik and David M. Gibson, Springer-Verlag, Berlin Heidelberg New York, 1986., p.163
Publication Date:
00/1986
Origin:
ADS
Bibliographic Code:
1986LNP...254..163G

Abstract

Contents: Global convection and differential rotation theory. Kinematic and magnetohydrodynamic dynamo theory for the bulk of the convection zone. Dynamos at the interface between the convection zone and radiative interior. Implications for future work.

Title:
The response of chromospheric emission lines to flares on YZ Canis Minoris
Authors:
Worden, S. P.; Schneeberger, T. J.; Giampapa, M. S.; Deluca, E. E.; Cram, L. E.
Affiliation:
AA(Sacramento Peak Observatory, Sunspot, NM)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 276, Jan. 1, 1984, p. 270-280. (ApJ Homepage)
Publication Date:
01/1984
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BALMER SERIES, CHROMOSPHERE, EMISSION SPECTRA, FLARE STARS, STELLAR FLARES, STELLAR SPECTRA, CONTINUOUS SPECTRA, H ALPHA LINE, SOLAR FLARES, SPECTRAL LINE WIDTH, STELLAR LUMINOSITY, UBV SPECTRA
DOI:
10.1086/161611
Bibliographic Code:
1984ApJ...276..270W

Abstract

Six flares of the dMe star YZ CMi have been observed with simultaneous photometry and high-dispersion, time-resolved spectroscopy.The spectra have temporal resolutions of 3 minutes with spectral resolutions of 0.24 Å. The largest observed flare had a U band amplitude of 1.5 mag. Hα and Hβ line profiles did not broaden during any of the observed flares, although the line center intensity increased by over a factor of 2 during some flares. After the initial increase in intensity, the emission line strength decreases but remains at enhanced levels for hours following U band flares. The Hα flare luminosity and total energy are compared to corresponding properties of solar flares.

Title:
A search for red-dwarf members of the Coma star cluster
Authors:
Deluca, E. E.; Weis, E. W.
Publication:
Astronomical Society of the Pacific, Publications, vol. 93, Feb.-Mar. 1981, p. 32-34. (PASP Homepage)
Publication Date:
02/1981
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL PHOTOMETRY, DWARF STARS, STAR CLUSTERS, ASTRONOMICAL PHOTOGRAPHY, COMA, SEARCHING, STELLAR LUMINOSITY, STELLAR MOTIONS, VISUAL PHOTOMETRY
Comment:
A&AA ID. AAA029.153.039
Bibliographic Code:
1981PASP...93...32D

Abstract

A photometric search for red dwarfs belonging to the Coma star cluster is reported. Observations in B, V, R and I were obtained for 88 stars in the region of the Coma cluster using a pulse-counting photometer with a GaAs photomultiplier attached to a 0.9-m reflector. Cluster membership of the stars was determined on the basis of the deviation of stellar position in V, (B-V) and V, (R-I) diagrams from the nominal main sequence. Of the 25 stars suggested as possible members by Artyukhina (1955) and the 29 additional stars suggested by Malmquist (1927), only three stars are found to be possible members on the basis of this criterion. The possible membership of only one of the two stars suggested by Argue and Kenworthy on the basis of proper motions and photographic photometry is confirmed. It is concluded that the number of red-dwarf members of the Coma cluster with V magnitudes between 10.5 and 15.5 is unlikely to be greater than ten.

Title:
Photometry of possible members of the Hyades cluster III
Authors:
Weis, E. W.; Deluca, E. E.; Upgren, A. R.
Affiliation:
AA(Van Vleck Observatory, Middletown, Conn.), AB(Van Vleck Observatory, Middletown, Conn.)
Publication:
Astronomical Society of the Pacific, Publications, vol. 91, Dec. 1979-Jan. 1980, p. 766-771. (PASP Homepage)
Publication Date:
12/1979
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ELECTROPHOTOMETRY, STAR CLUSTERS, STELLAR SPECTROPHOTOMETRY, VISUAL PHOTOMETRY, OORT CLOUD, TABLES (DATA)
Comment:
A&AA ID. AAA027.153.013
Bibliographic Code:
1979PASP...91..766W

Abstract

Photoelectric photometry in BVRI colors has been obtained for 61 stars in the region surrounding the Hyades cluster. Almost all stars observed here were found by Giclas or Luyten to possess proper motions resembling those of confirmed Hyades members. They cover the ranges between 0.6 and 1.7 in (B-V) and 0.2 and 1.3 in (R-I) and are thus mostly late G, K, and early M stars. Of these 61 stars, only 24 are found to be probable members and five are found to be possible members from their positions in either the V,(B-V) or V,(R-I) diagrams. Nonetheless, these probable members enrich the cluster well beyond the list of Pels, Oort, and Pels-Kluyver, especially in its southwestern quadrant.

Title:
Photometry of Praesepe in BVRI colors
Authors:
Upgren, A. R.; Weis, E. W.; Deluca, E. E.
Affiliation:
AA(Van Vleck Observatory, Middletown, Conn.)
Publication:
Astronomical Journal, vol. 84, Oct. 1979, p. 1586-1590. (AJ Homepage)
Publication Date:
10/1979
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
COLORIMETRY, LATE STARS, STAR CLUSTERS, STELLAR SPECTROPHOTOMETRY, UBV SPECTRA, ASTRONOMICAL CATALOGS, ASTRONOMICAL PHOTOMETRY, BINARY STARS, ELECTROPHOTOMETRY, MAIN SEQUENCE STARS
Comment:
A&AA ID. AAA026.153.013
DOI:
10.1086/112580
Bibliographic Code:
1979AJ.....84.1586U

Abstract

Results are reported for BVRI photoelectric photometry of 55 stars in the region of the Praesepe cluster. Distance moduli are derived independently from V, B-V and V, R-I diagrams. These diagrams indicate that five of the stars do not appear to be cluster members and that 13 others are possibly binary members of Praesepe. The remaining stars are found to define a sequence similar in slope to that of the Hyades and lying 3.0 mag below it. Best values of 6.20 + or - 0.05 mag for the modulus and 174 + or - 4 pc for the distance of Praesepe are adopted.