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Astron. Astrophys. Suppl. Ser. 139, 89-96

Analysis of evolution of NOAA 7912 active region on 19 October 1995

P. Rudawy1 - L. van Driel-Gesztelyi2,3 - B. Cader-Sroka1 - P. Mein2 - N. Mein2 - B. Schmieder2 - J.-M. Malherbe2 - B. Rompolt1

Send offprint request: P. Rudawy

Astronomical Institute of the Wroclaw University, PL 51622 Wroclaw, ul Kopernika 11, Poland
1 - Observatoire de Paris, Section de Meudon, F-92195 Meudon Principal Cedex, France
2 - Konkoly Observatory, Budapest, Pf. 67, H-1525, Hungary

Received January 28; accepted June 18, 1999


An analysis of a minor (B3.2) flare related to an X-ray jet in the reversed polarity NOAA 7912 active region is presented, focusing on various kinds of activity observed in the H$\alpha$ line with the MSDP instrument. Using complementary Yohkoh soft X-ray observations and a Kitt Peak magnetic field map we study the influence of a rather low and graduate energy release on filaments, fibrils and chromospheric brightenings and their relevant coronal features. We find that this small flare affected the entire AR and was associated with strong up- and downflows along remote fibrils and filaments, which appear to be connected by large-scale loops. It is shown that at least one of the observed brightenings was caused by downflow of the matter, thus, by the kinematic heating of the material. The filament in the vicinity of the flare footpoints changed the most: it broke into two parts, temporarily rose to higher altitudes inside the AR and even erupted outside of the AR, re-forming only three hours later. We show that even a minor flare can lead to important morphological and dynamical changes in an active region.

Key words: Sun: chromosphere -- Sun: activity -- Sun: filaments

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