2D Quantitative Spectral Analysis of a Flare Loop System

 Xiao-Ma Gu

Abstract

The 2D spectral profiles of {\ha} and CaII $\lambda 8542\AA$ lines are quantitatively analyzed for the limb flare loop system of November 11,1998 and the average velocity fields(V), integrated intensity fields(E) and the fields of profile asymmetric factor P are obtained for the loop system in the two lines. The velocity distribution shows that the red-shift velocity lies on the north of the loop system and the blue-shift on the south, it means the matter in loops falls down from the top towards its feet. Most profiles are asymmetric for the two lines, and most of them are blue asymmetric ones, there is no clear relationship between V and P. The distribution of E (the area where the values of E are bigger than 0.5$\times$10$^{7}$) shows that the forming height of CaII 8542$\AA$ line is much lower than that of {\ha} line.

A new method of "Multi-cloud model" (MCM) are applied to deal with asymmetric profiles and four parameters (Doppler width $\Delta\lambda_{D}$, Doppler shift $\Delta\lambda_{0}$ of the line, source function S and optical depth at the line center $\tau_{0}$) are derived quantitatively. We also compute the atomic number density $N_{2}$ (for{\ha} line), $N_{3}$ (for CaII 8542$\AA$ line) and the temperature T of the loop system, they are $\sim$ $10^{12}$, $10^{13}$ $cm^{-3}$ and12000 $\sim$ 15000 K respectively. A turbulent velocity $V_{t}$ within the loop system is estimated 20 $\sim$ 40 {\kms}.

The {\ha} profile at the loop top is very broad, it may be widened by a non-thermal effect when $\Delta\lambda_{D} > 1$ $\AA$, while the thermal radiation effect is very small, which can not solely explain the very wide profile.

 Authors: Gu X.M.1, 3, 4  Li K.J.1, 3  Ding M.D.2  Qu Z.Q.1, 3 Zhong S.H.1
 

  Organization: Yunnan Observatory
     Telephone: 86-871-3914018
           Fax: 86-871-3911845
        e-mail: xmgu@cosmos.ynao.ac.cn
       Address: P. O. Box 110
   Kunming,650011, P. R. China