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

摘要

X-ray and EUV observations are an important diagnostic of various plasmaparameters of the solar atmosphere during solar flares. Soft X-ray and EUVobservations often show coronal sources near the top of flaring loops, whilehard X-ray emission is mostly observed from chromospheric footpoints. CombiningRHESSI with simultaneous SDO/AIA observations, it is possible for the firsttime to determine the density, temperature, and emission profile of the solaratmosphere over a wide range of heights during a flare, using two independentmethods. Here we analyze a near limb event during the first of three hard X-raypeaks. The emission measure, temperature, and density of the coronal source isfound using soft X-ray RHESSI images while the chromospheric density isdetermined using RHESSI visibility analysis of the hard X-ray footpoints. Aregularized inversion technique is applied to AIA images of the flare to findthe differential emission measure (DEM). Using DEM maps we determine theemission and temperature structure of the loop, as well as the density, andcompare it with RHESSI results. The soft X-ray and hard X-ray sources arespatially coincident with the top and bottom of the EUV loop, but the bulk ofthe EUV emission originates from a region without co-spatial RHESSI emission.The temperature analysis along the loop indicates that the hottest plasma isfound near the coronal loop top source. The EUV observations suggest that thedensity in the loop legs increases with increasing height while the temperatureremains constant within uncertainties.