Hybrid modelling of chromospheric HXR flare sources in the flare loops

Measurements of vertical extents of the chromospheric hard X-ray (HXR) flare sources located at the solar limb based on the Ramaty High-Energy Spectroscopic Imager (RHESSI) observations show a significant inconsistency with the theoretical predictions based on the standard collisional thick target model. Using a hybrid flare code Flarix, we are able to model simultaneously and self-consistently the propagation, scattering and energy losses of electron beams with the power-law energy spectra and various initial pitch-angle distributions in a purely collisional approximation and concurrently the dynamic response of the heated chromosphere. Based on the resulting non-thermal electron distribution function and on the state of the ambient plasma in a heated singular flare loop, the time evolution of the corresponding non-thermal HXR sources are calculated. The results of our simulations indicate a possible explanation of the RHESSI based measurements.