Solar He-3-rich events and electron acceleration in two stages

The heating, acceleration, and enhancement of electrons in solar He-3-rich events are studied according to the two-stage acceleration model proposed f or the enhancement of He-3 and heavy ions. First, electrostatic ion cyclotr on instabilities destabilized by electron currents are theoretically and nu merically investigated for a plasma consisting mainly of H, He-4, and elect rons. Since the parallel phase velocities of the ion cyclotron waves are sm aller than around the electron thermal velocity, electrons can have strong Landau resonance (omega(r) - k(parallel to) upsilon(e, parallel to) = 0) wi th the ion cyclotron waves. Here omega(r) and k(parallel to) are, respectiv ely, the real frequency and wavenumber parallel to the external magnetic fi eld and upsilon(e,parallel to) is the parallel electron velocity. Second, p referential heating of electrons by the ion cyclotron waves is studied thro ugh the quasi-linear theory. It is shown that H cyclotron waves are very ef ficient at heating electrons through the Landau resonance. Third, these pre heated electrons can be further accelerated to high energies in the Fermi a cceleration process. The abundance ratio (e/H) of high-energy electrons and protons is estimated. The abundance ratio is very high when electrons are sufficiently heated relative to protons and agrees well with observations. Therefore, the present two-stage model explains all aspects of acceleration (He-3, electrons, and heavy ions) in flares in a self-consistent way.