Nonresonant ion-beam turbulence in solar flares

Abstract

Special type III radio bursts are attributed to low-energy, super-Alfvénic proton beams. Such beams are unstable against scattering by resonant and nonresonant parallel waves. The latter may dominate and are of two types, with long wavelengths and linear polarization, or else with shorter wavelengths and right/left-hand polarization. Extensions of Fowler's theorem to unstable beam plasmas indicate higher levels of magnetic field turbulence at shorter wavelengths, up to a sizeable fraction of the flare magnetic field. The beams become sub-Alfvénic before completely travelling down the loop, leading to considerable heating of the flare particles.