Time dependent ionization balance in solar flares

Abstract

We have analyzed the time evolution of solar flare X-ray spectra from He-like Fe, Ca and S ions measured for a 1992 September 6 flare by the Bragg Crystal Spectrometer (BCS) on the Yohkoh satellite. We derived time-dependent electron temperature, ion temperature, electron density as well as the ion density ratios such as n(Li-like)/n(He-like), n(Be-like)/n(He-like), n(B-like)/n(He-like) for Fe ions and n(He-like)/n(H) for Fe and Ca ions. The results show a deviation from ionization equilibrium. In this paper we investigate the origin of the deviation and consider time dependent ionization models assuming material flow in solar flares or multiple loops occurring with a short time period.