Redshift of the Ca XIX resonance line in solar flares observed with Yohkoh bragg crystal spectrometer

摘要

Among a total of 158 flares in which the soft X-ray morphologies present a single loop or a single- loop-dominated structure, about 16/100 show a redshift in the Ca XIX resonance line. The number dis- tribution of redshifted events on the solar disk exhibits a limb-increasing tendency. Having analyzed the implications of redshifts, we find only seven events in which the redshifts may marginally be the result of mass downflows along the loop, while the redshifts in the other events can be explained either by the model of chromospheric evaporation or by the contribution of satellite lines to the resonance line.