Speaker
Description
Recent observations by the Spectrometer/Telescope for Imaging X-rays (STIX) onboard Solar Orbiter have revealed deviations from the classical energy-altitude relation of hard X-ray (HXR) footpoint sources in solar flares. While the standard thick-target model predicts monotonic decrease of source height with increasing energy, STIX observations show non-monotonic features, including local maxima in source height as a function of energy.
We present results of a statistical study of HXR source heights based on a sample of solar flares observed by STIX. We investigate the occurrence, characteristic energies, densities, and heights of the observed anomalies and explore their possible physical origin.
To support the interpretation of the observation, we employ a numerical thick-target model describing the collisional transport of non-thermal electrons injected from the corona into the chromosphere. Preliminary simulations indicate that variations in the chromospheric density structure can modify the resulting energy-altitude relation.