High-temperature differential emission measure and altitude variations in the temperature and density of solar flare coronal X-ray sources

Jeffrey, N. L. S. , Kontar, E. P. and Dennis, B. R. (2015) High-temperature differential emission measure and altitude variations in the temperature and density of solar flare coronal X-ray sources. Astronomy and Astrophysics, 584, A89. (doi:10.1051/0004-6361/201526665)

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Abstract

The detailed knowledge of plasma heating and acceleration region properties presents a major observational challenge in solar flare physics. Using the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the high temperature differential emission measure, DEM(T), and the energy-dependent spatial structure of solar flare coronal sources are studied quantitatively. The altitude of the coronal X-ray source is observed to increase with energy by ~+0.2 arcsec/keV between 10 and 25 keV. Although an isothermal model can fit the thermal X-ray spectrum observed by RHESSI, such a model cannot account for the changes in altitude, and multi-thermal coronal sources are required where the temperature increases with altitude. For the first time, we show how RHESSI imaging information can be used to constrain the DEM(T) of a flaring plasma. We develop a thermal bremsstrahlung X-ray emission model with inhomogeneous temperature and density distributions to simultaneously reproduce: i) DEM(T), ii) altitude as a function of energy, and iii) vertical extent of the flaring coronal source versus energy. We find that the temperature-altitude gradient in the region is ~+0.08 keV/arcsec (~1.3 MK/Mm). Similar altitude-energy trends in other flares suggest that the majority of coronal X-ray sources are multi-thermal and have strong vertical temperature and density gradients with a broad DEM(T).

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Jeffrey, Dr Natasha and Kontar, Dr Eduard
Authors: Jeffrey, N. L. S., Kontar, E. P., and Dennis, B. R.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN:0004-6361
ISSN (Online):1432-0746
Copyright Holders:Copyright © 2015 EDP Sciences
First Published:First published in Astronomy and Astrophysics 584:A89
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.
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