Spectral Analysis of the Flare of 1998 November 11 based on the Multi-cloud Model

Abstract

We have obtained 2D spectra of Halpha and CaII lambda 8542Angstrom for the flare of 1998 November 11, and derived its 2D velocity field and integrated intensity field, The velocity distribution shows that the red-shift and blue-shift velocities lie respectively in the northern and southern parts of the flare and that the maximum velocity seems to be located in two footpoints of the flare loop system. The integrated intensity distribution shows that the CaII lambda 8542Angstrom line is formed at a lower height than the Halpha line. we used 'multi-cloud model' (MCM) to obtain four parameters for the two lines (Doppler width, Deltalambda(D), Doppler shift, Deltalambda(0), line source function, S, and optical depth at the line center, tau(0)). We also estimated the column number densities of hydrogen at the second level, N-2, and of the ionized calcium at the third level, N-3, as well as the kinetic temperature, T-c. The wide Halpha profile at the loop top may be explained by an overlapping of two or more elementary profiles. It is shown that the uncertainty in calibration does not affect the derived Doppler shift and line broadening, only the source function and optical depth.