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On the Accuracy of the Differential Emission Measure Diagnostics of Solar Plasmas. Application to SDO/AIA. II. Multithermal Plasmas

TitreOn the Accuracy of the Differential Emission Measure Diagnostics of Solar Plasmas. Application to SDO/AIA. II. Multithermal Plasmas
Type de publicationJournal Article
Year of Publication2012
AuteursGuennou, C, Auchere, F, Soubrie, E, Bocchialini, K, Parenti, S, Barbey, N
JournalThe Astrophysical Journal Supplement SeriesThe Astrophysical Journal Supplement Series
Volume203
Pagination26
Date PublishedDecember 1, 2012
ISBN Number0067-0049
Mots-clésplasmas, Sun: corona, Sun: UV radiation
Résumé

Differential emission measure (DEM) analysis is one of the most used diagnostic tools for solar and stellar coronae. Being an inverse problem, it has limitations due to the presence of random and systematic errors. We present in this series of papers an analysis of the robustness of the inversion in the case of SDO/AIA observations. We completely characterize the DEM inversion and its statistical properties, providing all the solutions consistent with the data along with their associated probabilities, and a test of the suitability of the assumed DEM model. While Paper I focused on isothermal conditions, we now consider multithermal plasmas and investigate both isothermal and multithermal solutions. We demonstrate how the ambiguity between noises and multithermality fundamentally limits the temperature resolution of the inversion. We show that if the observed plasma is multithermal, isothermal solutions tend to cluster on a constant temperature whatever the number of passbands or spectral lines. The multithermal solutions are also found to be biased toward near-isothermal solutions around 1 MK. This is true even if the residuals support the chosen DEM model, possibly leading to erroneous conclusions on the observed plasma. We propose tools for identifying and quantifying the possible degeneracy of solutions, thus helping the interpretation of DEM inversion.

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