RHESSI and SDO/AIA observations of the chromospheric and coronal plasma parameters during a solar flare

TL;DR

This study combines RHESSI and SDO/AIA observations to analyze plasma parameters during a solar flare, revealing detailed temperature and density structures across different atmospheric heights.

Contribution

It introduces a novel combined analysis method using two independent techniques to determine plasma parameters across a wide range of heights during a solar flare.

Findings

Coronal source temperature and density are derived from soft X-ray images.

Chromospheric density is estimated from hard X-ray footpoints.

EUV DEM analysis reveals the temperature and density structure of the flare loop.

Abstract

X-ray and EUV observations are an important diagnostic of various plasma parameters of the solar atmosphere during solar flares. Soft X-ray and EUV observations often show coronal sources near the top of flaring loops, while hard X-ray emission is mostly observed from chromospheric footpoints. Combining RHESSI with simultaneous SDO/AIA observations, it is possible for the first time to determine the density, temperature, and emission profile of the solar atmosphere over a wide range of heights during a flare, using two independent methods. Here we analyze a near limb event during the first of three hard X-ray peaks. The emission measure, temperature, and density of the coronal source is found using soft X-ray RHESSI images while the chromospheric density is determined using RHESSI visibility analysis of the hard X-ray footpoints. A regularized inversion technique is applied to AIA images of the flare to find the differential emission measure (DEM). Using DEM maps we determine the emission and temperature structure of the loop, as well as the density, and compare it with RHESSI results. The soft X-ray and hard X-ray sources are spatially coincident with the top and bottom of the EUV loop, but the bulk of the EUV emission originates from a region without co-spatial RHESSI emission. The temperature analysis along the loop indicates that the hottest plasma is found near the coronal loop top source. The EUV observations suggest that the density in the loop legs increases with increasing height while the temperature remains constant within uncertainties.