Astronomy and Astrophysics – Astronomy
Scientific paper
May 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...194.7907w&link_type=abstract
American Astronomical Society, 194th AAS Meeting, #79.07; Bulletin of the American Astronomical Society, Vol. 31, p.964
Astronomy and Astrophysics
Astronomy
Scientific paper
On September 27, 1998, Big Bear Solar Observatory (BBSO) and Transition Region and Coronal Explorer (TRACE) coordinated observations from 16:00 to 19:00 UT to study properties of microflares on AR NOAA #8340. Fortuitously, a C5.2 flare occurred at 16:30UT in this active region. Hα and magnetograph movies were obtained at BBSO; CIV 1550 Angstroms, FeIX 171 Angstroms, and FeXII 195 Angstroms movies were obtained by TRACE; both with a cadence about 1 minute. In this paper, we concentrate on the study of magnetic properties of 70 CIV microflares, as well as their relationship to the C5.2 flare. We obtained the following results: (1) We found two kinds of microflares: (a) microflares of transient brightenings with a time scale of 1 to 5 minutes (impulsive events). 90% of the microflares are of this form. Most of the events in this category are associated with well defined magnetic neutral lines, although a few of them are not located near a neutral line; and (b) microflares lasting half an hour or longer (persistent events). Seven events in three clusters belong to this category. All three sites are associated with a dominant magnetic polarity plus a very small element of opposite polarity. (2) More than a third of the impulsive microflares occurred near the C5.2 flare site indicating that a local instability is responsible for both the C5.2 flare and microflares. This indirectly support the avalanche theory of flare energy release, which predicts that a big flare may be associated with many small flares. Based on the morphologies of those events, we postulate that the persistent events may be due to loop interaction; while impulsive events may be associated with sheared loop structure.
Chae Jongchul
Goode Philip
Lee Chaohong
Qiu Jianwei
Wang Hai-Hong
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