EDP Sciences
Free access
Volume 380, Number 2, December III 2001
Page(s) 704 - 713
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20011251

A&A 380, 704-713 (2001)
DOI: 10.1051/0004-6361:20011251

Two-dimensional multi-parameter fields of a limb flare loop system

X. M. Gu1, 2, J. P. Dun1 and S. H. Zhong1

1  Yunnan Observatory, CAS, Kunming 650011 and National Astronomical Observatories, CAS, Beijing 100012, PR China
2  United Laboratory of Optical Astronomy, CAS, Shanghai 200030, PR China

(Received 20 November 2000 / Accepted 7 August 2001 )

The 2D H$_{\beta}$ spectral data of the post-flare loop system (PFLs) of August 17, 1989 are obtained and analyzed quantitatively. Four physical parameters (the line-of-sight velocity V//, column number density of the hydrogen atoms at the second level along the line-of-sight direction N2, the excitation temperature $T_{\rm ex}$ and the micro-turblence velocity $V_{\rm t}$) and their 2D distributions are derived. The 2D fields of V//, N2, $T_{\rm ex}$ and $V_{\rm t}$ exhibit inhomogeneous and asymmetric properties in two loop legs. Red-shift velocities in the south leg are smaller than those of blue shift in the north leg where the velocity reaches 60 km s-1. The values of N2 and $T_{\rm ex}$ in the south leg are all much higher than those in the north leg, N2 ranges between 0.5 to $4.5\times 10^{13}$ cm-2, while $T_{\rm ex}$ ranges from 0.8 to $2.2 \times 10^{4}$ K, lower at the top part than in the two legs. A high temperature region is located in the middle of the south leg. $V_{\rm t}$ at the top part is greater than that in the two legs, with the average being 30~40 km s-1. Electron density $n_{\rm e}$ and electron pressure $P_{\rm e}$ are estimated at 0.2~ $0.6\times 10^{11}$ cm-3 and at 0.04~0.12 dyn cm-2, respectively. These results are compared with those obtained from the PFLs of 1984 February 18.

Key words: Sun: flares -- Sun: fundamental parameters

Offprint request: Xiao Ma Gu, ssg@public.km.yn.cn

© ESO 2001