Charge state distributions of iron in impulsive solar flares: Importance of stripping effects

Abstract

A model of stochastic acceleration of heavy ions by Alfvén wave turbulence has been developed. It takes into account spatial diffusion, Coulomb losses, and the possibility of charge changes for ions during stochastic acceleration. The main processes influencing the ionic charge states are the stripping by thermal electrons and protons as constituents of a surrounding medium and dielectronic and radiative recombination. We have calculated energy spectra and charge distributions of nonthermal Fe ions as a sample species. The dependence of the charge distributions and energy spectra of iron on the parameters of the plasma (temperature and number density) is studied. We compare our results with measurements to date of the mean charge of iron in impulsive solar flare events and conclude that they indicate source plasma ionization temperatures between 6□×10⁶ and 10⁷K.