Astron. Astrophys. 324, 289-297 (1997)

Post-flare loops of May 16, 1981

Spectral analysis

Xiao-Ma Gu ^{1, 2}, You-Ji Ding ², Zhi Luo ² and Brigitte Schmieder <sup>3

1</sup> CCAST (World Laboratory), P.O. Box 8730, Beijing, 100080
² Yunnan Observatory, P.O. Box 110, Kunming, YN 650011, China
³ Observatoire de Paris- Meudon, DASOP, URA 2080, F-92195 Meudon Principal Cedex, France

Received 24 September 1996 / Accepted 21 November 1996

Abstract

We present the analysis of H spectra obtained during a two-ribbon flare observed on the solar disk on May 16, 1981 at Yunnan Observatory with the Spectra-Spectroheliograph (SSHG). The complicated asymmetric profiles produced by the post-flare loops overlying flare ribbons are analysed with a fast method based on the cloud model method. This method takes into account the bright background of the loops and allows computation of the physical quantities of loops crossed by the slit: velocity field, optical thickness, source function and Doppler width. Using the scanning spectra of the region, we obtain 2-D maps of these parameters. The validity of the method used is compared with other methods and the sensitivity of parameters to solution is discussed in details. The results obtained with this method are compared with those given by Heinzel et al. (1992) using a fully non-LTE approach.

Key words: Sun: flares methods: data analysis

Send offprint requests to: Xiaoma-Gu

Contents

• 1. Introduction
• 2. Instruments and observations
• 3. Method of spectral analysis
• 4. Validity of the method
• 5. Physical parameters of the loop and the bright background
• 6. Electron density and gas pressure of the loops
• 7. Conclusion
• Acknowledgements
• Appendix: mathematical method
• References

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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