DERIVATION OF STOCHASTIC ACCELERATION MODEL CHARACTERISTICS FOR SOLAR FLARES FROM <i>RHESSI</i> HARD X-RAY OBSERVATIONS

Abstract

The model of stochastic acceleration of particles by turbulence has been\nsuccessful in explaining many observed features of solar flares. Here we\ndemonstrate a new method to obtain the accelerated electron spectrum and\nimportant acceleration model parameters from the high resolution hard X-ray\nobservations provided by the Reuven Ramaty High Energy Solar Spectroscopic\nImager (RHESSI). In our model, electrons accelerated at or very near the loop\ntop produce thin target bremsstrahlung emission there and then escape downward\nproducing thick target emission at the loop footpoints. Based on the electron\nflux spectral images obtained by the regularized inversion of the RHESSI count\nvisibilities, we derive several important parameters for the acceleration\nmodel. We apply this procedure to the 2003 November 03 solar flare, which shows\na loop top source up to 100--150 keV in hard X-ray with a relatively flat\nspectrum in addition to two footpoint sources. The results imply presence of\nstrong scattering and a high density of turbulence energy with a steep spectrum\nin the acceleration region.\n