On the Acceleration of Relativistic Electrons in Solar Proton Flares

The acceleration mechanism of relativistic electrons in solar flares is considered by taking into account the physical condition of accelerating regions such as plasma density and magnetic field intensity. For the electrons of the kinetic energy range 10 MeV, it is shown that the Fermi acceleration is more effective than the betatron acceleration. The most plausible values of the plasma number density and the strength of sunspot magnetic fields in the accelerating regions are estimated to be cm-3 and gauss, respectively. This suggests that the accelerating regions are located somewhere above the Ha-flare regions. The accelerating regions may be identified with the triggering regions of solar flares where 8irPkin/B2 << 1 (Fkin: kinetic plasma pressure; B: sunspOt magnetic field intensity) and so they approximately satisf the force-free condition as regards magnetic field configuration. The accelerated electrons and their relation to the emission of type IV radio bursts are briefly discussed. Key words: solar proton flares - relativistic electrons