Last Updated: 20160111

ISSI AtomicHelioStatistics Collaboration

Line Ratio problem

for Bern Meeting

11-13 May 2015

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One way to focus our efforts during the first meeting could be to organize an attack on a less complicated problem than the full temperature inversion problem. We could, for example, investigate inferring the plasma density from simple line ratios, because it touches upon most of the aspects of the problem while minimizing complexity. The Fe XIII 203.826/202.044 ratio is commonly used in the analysis of Hinode/EIS observations and there are similar ratios in stellar observations. Considering the line ratio problem for a specific pair of lines should allow us to make some rapid progress on incorporating uncertainties in the observation of the line profile, atomic data, and instrument calibration into a realistic analysis while getting everyone on the same page.


Papers of interest

Warren, H.P., Winebarger, A.R., Mariska, J.T., Doschek, G.A., & Hara, H., 2008, Observation and Modeling of Coronal ``Moss'' With the EUV Imaging Spectrometer on Hinode, ApJ, 677, 1395
2008ApJ...677.1395W [ADS]
IOP [.pdf]
Martens, P.C.H., Kankelborg, C.C., & Berger, T.E., 2000, On the Nature of the ``Moss'' Observed by TRACE, ApJ, 537, 471
2000ApJ...537..471M [ADS]
Berger, T.E., De Pontieu, B., Schrijver, C.J., & Title, A.M.,, 1999, High-resolution Imaging of the Solar Chromosphere/Corona Transition Region, ApJ, 519, 97
1999ApJ...519L..97B [ADS]
Peres, G., Reale, F., & Golub, L., 1994, Loop models of low coronal structures observed by the Normal Incidence X-Ray Telescope (NIXT), ApJ, 422, 412
1994ApJ...422..412P [ADS]


Chianti Monte Carlo
Realizations of density-sensitive Fe 13 ratios generated by imposing a Gaussian uncertainty model on the line strengths in Chianti (calculations by H. Warren) is available on github.
Description of files [.pdf] (HW 2016-jan-14)
Fe 13 (200.021, 201.121, 202.044, 203.152, 203.826) emissivities tables [hdf] (HW 2016-jan-13)
R script to read in the emissivities [.R] (HW 2016-jan-13)
Fe 13 ratios showing density sensitivity [.jpeg] (HW 2016-jan-13)
Fe 13 ratios variations [.png] (HD 2016-jan-13)
Temperature sensitivity of Fe 13 density-sensitive ratio curves [.png] (VK 2016-jan-13)
EIS data from moss regions
spectra [.txt]
Notes on data and context [.pdf]
XRT data coincident with EIS data above
xrt_20120421_165329.tar.gz [fits/.tar.gz]
XRT 2012apr21 16:55 Be/thin movie [.mp4]
XRT 2012apr21 16:53:46 Be/thin


Papers of interest

Ness, J.-U., Brickhouse, N.S., Drake, J.J., & Huenemoerder, D.P., 2003, Modeling the Ne IX Triplet Spectral Region of Capella with the Chandra and XMM-Newton Gratings, ApJ, 598, 1277
2003ApJ...598.1277N [ADS]
IOP [.pdf]
Smith, R.K., Chen, G., Kirby, K., & Brickhouse, N.S., 2009, A New Calculation of Ne IX Line Diagnostics, ApJ, 700, 679
2009ApJ...700..679S [ADS]
IOP [.pdf]
Smith, R.K., Brickhouse, N.S., Liedahl, D.A., & Raymond, J.C., 2001, Collisional Plasma Models with APEC/APED: Emission-line Diagnostics of Hydrogen-like and Helium-like Ions, ApJ, 556, L91
2001ApJ...556L..91S [ADS]
IOP [.pdf]


O8 and O7rif +ve and -ve order counts and background counts for all Chandra grating observations of Capella
Capella_O8O7rif.rdb [.rdb]
The file lists the time of observation, exposure duration, the areal weight that should be assigned to the background counts, source and background counts, and the effective areas for the +ve and -ve orders
Chianti Monte Carlo
Realizations of density-sensitive O 7 and O 8 ratios generated by imposing a Gaussian uncertainty model on the line strengths in Chianti (calculations by H. Warren) is available on github.
Description of files [.pdf]
O VII (21.6, 21.8, 22.1) emissivities tables [hdf]
O VIII (18.96) emissivities tables [hdf]
R script to read in the emissivities [.R]
O 7 ratios variations [.jpg] (HD 2016-jan-13)
Temperature sensitivity of O 7 and O 8 density-sensitive ratio curves [.png] (VK 2016-jan-13)
Density sensitivity of O7r/O8 temperature-sensitive ratio curve [.png] (VK 2016-jan-13)
Co-added Capella spectra from various Chandra detector/grating combinations. The file headers contain a description of the columns.
ACIS/HEG 1st order [.rdb]
ACIS/MEG 1st order [.rdb]
ACIS/LEG 1st order [.rdb]
HRC/LEG 1st order [.rdb]
* rdb files are tab-separated ascii tables, with two additional uncommented lines -- one for column names, and one listing the type of data in the column (N for numeric, S for character strings; these files only have numerical values)
* Acronyms:
ACIS : Advanced CCD Imaging Spectrometer
HRC : High Resolution Camera
HETGS : High-Energy Transmission Grating Spectrometer (has two arms, HEG and MEG)
LETGS : Low-Energy Transmission Grating Spectrometer (has one arm)
HEG : High Energy Grating spectrum arm of HETGS
MEG : Medium Energy Grating spectrum arm of HETGS
LEG : Low Energy Grating spectrum arm from LETGS
The bin sizes are constant in Angstrom, but differ for each case.
* The instrumental line widths are smallest for HEG and largest for LEG.
* The effective exposure is the product of effective area and exposure time for each included observation; the total exposure is in the headers of the rdb files.
* The background is collected along a strip adjacent to the source region, and its area relative to the source area is listed as BKGSCL in the headers of the rdb files.
* Details about the Chandra X-ray Observatory are available in the Proposers' Observatory Guide ([.html], [.pdf]).
* Calibration information about Chandra is available at



A snapshot from a 3D MHD simulation of a twisted flux tube. These simulation results can be used to forward model plasma properties expected from a plausible distribution of densities and temperatures along the line of sight. : python script to read HDF5 data files
data_0180.h5.gz [HDF5/.gz]
data_0180.idl.gz [IDL/.gz]

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