Hard X‐Rays from Neutralized Ion Beams in Solar Flares

Abstract

Under suitable conditions, hard X-rays (HXRs) may be emitted by a neutralized proton beam due to the "heating" of the electrostatically dragged electrons in collisions with a nearly neutral background atmosphere. A simple estimate is made generalizing this HXR emission mechanism to heavier ions dragging a neutralizing electron current. Recent gamma-ray results on the energy content of flare ions of ≥1 MeV nucleon-1 are used to estimate the total HXR yield above 20 keV or so which would be expected from these processes, and in 19 flares the results are compared with HXR data in the same events. It is found that only in two flares are the neutral beam HXRs clearly important and that in a few others they may be significant. In most events, however, the neutral beam HXR contribution is small, though the ion energy is comparable with that of electrons.