The Magnetic Topological Structure and Energy of the 2B/X2 Flare in NOAA 8100 |
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Authors: | Yihua Yan Yang Liu Maki Akioka Fengsi Wei |
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Institution: | (1) National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China;(2) Communications Research Laboratory, Hiraiso Solar Terrestrial Research Center, 3601 Isozaki, Hitachinaka, Ibaraki 311-1202, Japan;(3) Laboratory of Heliospheric Physics, CSSAR, Chinese Academy of Sciences, Beijing, 100080, China |
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Abstract: | In this paper, we reconstruct the finite energy force-free magnetic field of the active region NOAA 8100 on 4 November 1997
above the photosphere. In particular, the 3-D magnetic field structures before and after a 2B/X2 flare at 05:58 UT in this
region are analyzed. The magnetic field lines were extrapolated in close coincidence with the Yohkoh soft X-ray (SXR) loops accordingly. It is found that the active region is composed of an emerging flux loop, a complex loop
system with differential magnetic field shear, and large-scale, or open field lines. Similar magnetic connectivity has been
obtained for both instants but apparent changes of the twisting situations of the calculated magnetic field lines can be observed
that properly align with the corresponding SXR coronal loops. We conclude that this flare was triggered by the interaction
of an emerging flux loop and a large loop system with differential magnetic field shear, as well as large-scale, or open field
lines. The onset of the flare was at the common footpoints of several interacting magnetic loops and confined near the footpoints
of the emerging flux loop. The sheared configuration remained even after the energetic flare, as demonstrated by calculated
values of the twist for the loop system, which means that the active region was relaxed to a lower energy state but not completely
to the minimum energy state (two days later another X-class flare occurred in this region). |
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