Time-match semi-empirical models of the chromospheric flare on 3 February, 1983

Abstract

Spectra of a 2B flare on 3 February, 1983 were observed simultaneously at Hα, Hβ, and Can H, K lines with a multichannel spectrograph in the solar tower telescope of Nanjing University. The flare occurred in an extended region of penumbra at S 17 W07 from 05 : 41 to 07 : 00 UT. By use of an iterative method to solve the equations describing hydrostatic, radiative, and statistical equilibrium for hydrogen and ionized calcium atoms, five semi-empirical models corresponding to different times of the chromospheric flare have been computed. The results show that after the beginning of the flare, the heating of the chromosphere starts and the transition layer begins to be displaced downwards. However, during the impulsive phase the flare chromospheric region has a rapid outward expansion followed by a quick downward contraction. At the same time the transition layer starts to ascend and then descend again. After the Hα intensity maximum, the flare chromospheric region continues to condense and attains its most dense phase more than ten minutes after the maximum. Finally, the flare chromospheric region returns slowly to the normal chromospheric situation.