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Wave-like Formation of Hot Loop Arcades

2015; Springer Science+Business Media; Volume: 290; Issue: 10 Linguagem: Inglês

10.1007/s11207-015-0769-x

1573-093X

A. A. Reva, S. V. Shestov, I. V. Zimovets, С. А. Богачев, Sergey Kuzin,

Geomagnetism and Paleomagnetism Studies

We present observations of hot arcades made with the Mg xii spectroheliograph onboard the CORONAS-F mission, which provides monochromatic images of hot plasma in the Mg xii 8.42 Å resonance line. The arcades were observed to form above the polarity inversion line between active regions NOAA 09847 and 09848 at four successive episodes: at 09:18, 14:13, and 22:28 UT on 28 February 2002, and at 00:40 UT on 1 March 2002. The evolution of the arcades can be described as: a) a small flare (precursor) appeared near the edge of the still invisible arcade, b) the arcade brightened in a wave-like manner – closer loops brightened earlier, and c) the arcade intensity gradually decreased in ${\approx}\,1~\mbox{h}$ . The estimated wave speed was ${\approx}\,700~\mbox{km}\,\mbox{s}^{-1}$ , and the distance between the hot loops was ${\approx}\,50~\mbox{Mm}$ . The arcades formed without visible changes in their magnetic structure. The arcades were probably heated up by the instabilities of the current sheet above the arcade, which were caused by a magnetohydrodynamic wave excited by the precursor.