A Hard X-ray Two-Ribbon Flare Observed with Yohkoh/HXT |
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Authors: | Masuda S Kosugi T Hudson HS |
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Institution: | (1) Solar-Terrestrial Environment Laboratory, Nagoya University, 3-13, Honohara, Toyokawa, Aichi 442-8507, Japan;(2) Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan |
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Abstract: | The Yohkoh hard X-ray telescope (HXT) observed hard X-rays from the impulsive phase of a long-duration event (LDE) occurring on 14 July
2000. The Yohkoh soft X-ray telescope (SXT) and other instruments observed a large arcade, with width and length ∼30 000 km and ∼120 000 km,
respectively. In hard X-rays, for the first time, a two-ribbon structure was clearly observed in the energy range above 30 keV.
This result suggests that electrons are in fact accelerated in the whole system of this arcade, not merely in a particular
dominant loop. We analyzed the motions of bright kernels in the two hard X-ray ribbons in detail. Assuming these bright kernels
to be footpoints of newly reconnected loops, we infer from their motions that the loops reconnecting early are highly sheared,
while the loops reconnecting later are less sheared. We have also analyzed the hard X-ray spectra of the two ribbons independently.
At the outer edge of a ribbon, the spectrum tends to be harder than that in the inner edge. This suggests that higher-energy
electrons precipitate at the footpoints of outer loops and lower ones do at those of inner loops. We discuss what kind of
model can support this tendency. |
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