OBSERVATIONS OF CHROMOSPHERIC FLARE RE-BRIGHTENINGS
- Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz (Austria)
- Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria)
- Hvar Observatory, Faculty of Geodesy, Kaciceva 26, HR-1000 Zagreb (Croatia)
- Astronomical Institute of the Academy of Sciences of the Czech Republic, 25165 Ondrejov (Czech Republic)
We investigate an active region that produced three C-class flares and one M-class flare within 2.5 hr. The morphology and location of the C-flares indicate that these events constitute a set of homologous flares. Radio observations indicate the occurrence of a downward-moving plasmoid during the impulsive phase of the M flare. We use TRACE 1700 A filtergrams and SOHO Michelson Doppler Imager magnetograms to examine the character of the UV brightenings; i.e., we search for re-brightenings of former flare areas both across the series of events and within one and the same event. We find that essentially the same footpoints re-brighten in each C flare. Based on the progression of both the derived magnetic flux change rate and the observed Radio Solar Telescope Network microwave emission, we speculate about a further re-brightening during the decay phase of the M flare as a further member of the series of homologous flares. We conclude that the 'postflare' field is driven to repeated eruption by continuous, shear-increasing, horizontal, photospheric flows, as one end of the involved magnetic arcade is anchored in the penumbra of a large sunspot. The observed motion pattern of the UV kernels indicates that the arcade evolves during the series of events from a both highly sheared and heavily entangled state to a still sheared but more organized state.
- OSTI ID:
- 21457057
- Journal Information:
- Astrophysical Journal, Vol. 719, Issue 2; Other Information: DOI: 10.1088/0004-637X/719/2/1750; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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