A Correlation between Proton Events and Hα Flares and its Possible Interpretation

Abstract

Comparing space proton event data obtained during 1970-1980 with their identified H flare signatures we discover a peculiar correlation between them, according to which weak and small H flares can also produce proton events, and we reveal a characteristic triangle distribution of H flares accompanying proton events. In order to explain such feature of proton events, we accept the acceleration mechanism by DC electric field. To deduce the parallel electric field we use the elec- tric current helicity (or force-free parameter ) determined by the Huairou vector magnetograph. A comparison of Ek with E? shows that the former is negligible in flaring sites. We show that in the flaring current sheet ion-anisotropy is gener- ated, and it, in turn, gives rise to ion-anisotropic instability which competes with electric acceleration to give one possibility: the acceleration by DC electric field or annihilation of the built-up energy. The competition of DC acceleration and ion- anisotropic instability annihilation in the current sheet gives a possible explanation for the above-mentioned triangle character of the distribution.