[Untitled]
In: Solar Physics, Jg. 195 (2000), S. 381-399
Online
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Zugriff:
This report seeks to introduce the reader to a set of observations made during the decay phase of long-duration event (LDE) flares on the Sun. In a number of events, the soft X-ray images from Yohkoh SXT indicate a downward-directed flow field in the region immediately above the flare arcade. The prototypical event is the M5 flare of 20 January 1999, presented by McKenzie and Hudson (1999); since the time that paper was completed, eleven more events, all related to coronal mass ejections, have been found in the interval 1 January 1998 to 8 May 1999. As in the 20 January event, the speeds of downflow are 45–500 km s−1, lower than both the free fall speed and the typically assumed Alfven speed. A comparison is drawn between the SXT observations and the EUV and Hα data, where such are available. Important additions to our knowledge since the first paper are: (i) the motion is evidenced by both dark and bright (i.e., X-ray emitting) features, some of which may have a loop-like morphology; (ii) no cool counterparts have been detected in Hα or EUV observations. The data are compared to the expected appearance according to two likely (and opposing) interpretations: an `above-the-arcade coronal rain' interpretation and a `shrinking magnetic flux tube' interpretation. In the current standard explanation of the formation of post-CME arcades, motion of the latter type may be related to outflow from a reconnection site. Movies depicting some of the flare events are on the accompanying CD-ROM.
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Autor/in / Beteiligte Person: | McKenzie, David E. |
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Zeitschrift: | Solar Physics, Jg. 195 (2000), S. 381-399 |
Veröffentlichung: | Springer Science and Business Media LLC, 2000 |
Medientyp: | unknown |
ISSN: | 0038-0938 (print) |
DOI: | 10.1023/a:1005220604894 |
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