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

Kontar Eduard, eduard@astro.gla.ac.uk, University of Glasgow, United Kingdom
Battaglia Marina, University of Applied Sciences and Arts Northwestern, Switzerland

Abstract
X-ray and EUV observations are an important diagnostic tools 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 the 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 during a flare, using two independent methods. Here we analyzed a near limb event during the hard X-ray peak. 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(T). Using DEM maps, we determine the density and temperature structure of the loop and compare it with RHESSI results. We find that the EUV emission measure is one to two orders of magnitude lower than RHESSI and GOES emission measures. The most likely explanation is that the bulk of the plasma at the observed time is at a higher temperature than the AIA sensitivity range.