Abstract
We have studied the time evolution of BCS spectra of He - like S (15),
Ca(19) and Fe(25) ions
observed by the Yohkoh satellite for solar flares on 6th September 1992
at 05:05 (M2.4 class) and
08:59(M3.3 class). Electron temperatures are derived through the fit of
the synthetic spectra to
the observed ones. Apparent ion temperatures are derived from the line
width of S(15) and Ca(19)
spectra. The blue shifted component in the rising phase is separated
from the main component of
the Ca(19) spectra. The emission measures are derived from the spectra
without assuming
ionization equilibrium and solar abundances for the first time. The time
variation of these
parameters are compared with hard X-rays, soft X-rays and radio
measurements. In the
preheating phase, the moderate increase of thermal plasma with
turbulence indicated from the line
width is observed. The time evolution of the blue shift component
coincides with that of the burst
in hard X-rays and microwaves which are produced by non-thermal high
energy electrons. The
ion density ratios derived from the spectra show a time-dependent non
equilibrium ionization.
They are shifted from the equilibrium values indicating an ionizing
plasma.