Determination of differential emission measure from solar extreme ultraviolet images

Su, Y., Veronig, A. M., Hannah, I. G. , Cheung, M. C.M., Dennis, B. R., Holman, G. D., Gan, W. and Li, Y. (2018) Determination of differential emission measure from solar extreme ultraviolet images. Astrophysical Journal Letters, 856(1), L17. (doi: 10.3847/2041-8213/aab436)

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The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) has been providing high-cadence, high-resolution, full-disk UV-visible/extreme ultraviolet (EUV) images since 2010, with the best time coverage among all the solar missions. A number of codes have been developed to extract plasma differential emission measures (DEMs) from AIA images. Although widely used, they cannot effectively constrain the DEM at flaring temperatures with AIA data alone. This often results in much higher X-ray fluxes than observed. One way to solve the problem is by adding more constraint from other data sets (such as soft X-ray images and fluxes). However, the spatial information of plasma DEMs are lost in many cases. In this Letter, we present a different approach to constrain the DEMs. We tested the sparse inversion code and show that the default settings reproduce X-ray fluxes that could be too high. Based on the tests with both simulated and observed AIA data, we provided recommended settings of basis functions and tolerances. The new DEM solutions derived from AIA images alone are much more consistent with (thermal) X-ray observations, and provide valuable information by mapping the thermal plasma from ~0.3 to ~30 MK. Such improvement is a key step in understanding the nature of individual X-ray sources, and particularly important for studies of flare initiation.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Hannah, Dr Iain
Authors: Su, Y., Veronig, A. M., Hannah, I. G., Cheung, M. C.M., Dennis, B. R., Holman, G. D., Gan, W., and Li, Y.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal Letters
Publisher:American Astronomical Society
ISSN (Online):2041-8213
Published Online:23 March 2018
Copyright Holders:Copyright © The American Astronomical Society
First Published:First published in Astrophysical Journal Letters 856(1):L17
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
617954The many scales of flaring energy release on the SunIain HannahThe Royal Society (ROYSOC)UF120063S&E P&A - PHYSICS & ASTRONOMY