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

Jeffrey, Natasha, Kontar, Eduard P. and Dennis, Brian R. (2015) High-temperature differential emission measure and altitude variations in the temperature and density of solar flare coronal X-ray sources. Astronomy & Astrophysics, 584. A89. ISSN 0004-6361

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Official URL: https://doi.org/10.1051/0004-6361/201526665

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 were studied quantitatively. The altitude of the coronal X-ray source was 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 developed 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: Article
Uncontrolled Keywords: Sun: flares; Sun: corona; Sun: X-rays, gamma rays; Sun: particle emission
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Elena Carlaw
Date Deposited: 09 Sep 2019 14:54
Last Modified: 11 Oct 2019 13:01
URI: http://nrl.northumbria.ac.uk/id/eprint/40605

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