Imaging spectroscopy of hard X-ray sources in solar flares using regularized analysis of source visibilities

The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) uses rotational modulation synthesis for imaging hard X-ray flares with unprecedented spatial and spectral resolution. As the spacecraft rotates, imaging information is encoded as rapid time-variations of the detected flux. We introduce a novel method for imaging spectroscopy analysis of hard X-ray emission which reconstructs electron flux maps at different energies involving regularized inversion of X-ray count visibility spectra (i.e., direct, calibrated measurements of specific Fourier components of the source spatial structure). Starting from the reconstructed electron images it is possible to extract and compare electron flux spectra from different regions, which is a crucial step for the comprehension of the acceleration mechanisms during the solar flare.