GENERATION OF SOLAR H-ALPHA IMPACT POLARIZATION BY FRAGMENTED EVAPORATIVE UPFLOWS

In this paper a novel mechanism is proposed for the generation of H al pha impact polarization: observed during some solar flares. Rather tha n being generated by the primary particle beams transporting energy fr om the chromosphere to the corona, we suggest that following heating, the solar chromosphere evaporates in a fragmented manner, and that imp act excitations in the regions of interaction of hot evaporating and c ool nonevaporating material locally generates impact-polarized H alpha emission. This thermal upflow model is more consistent with the large areas and times over which polarization is observed than are beam mod els. A simple model for the process is given, and the resulting polari zation is calculated and compared with observations, under two assumpt ions about the number density of neutral particles in the interaction regions.