Abstract Comparing space proton event data obtained during 1970--1980 with their identified Hα flare signatures we discover a peculiar correlation between them, according to which weak and small Hα flares can also produce proton events, and we reveal a characteristic ``triangle" distribution of Hα 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 electric current helicity (or force-free parameter α) determined by the Huairou vector magnetograph. A comparison of E‖ with E⊥) shows that the former is negligible in flaring sites. We show that in the flaring current sheet ion-anisotropy is generated, 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.

Keywords Sun: flares --- Sun: particle emission

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