Wave-like Formation of Hot Loop Arcades

Abstract

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 A 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 arcades all evolved in the same way: 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 h. The estimated wave speed was $\approx$ 700 km s${}^{-1}$, and the distance between the hot loops was $\approx$ 50 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 an MHD wave excited by the precursor.

Published in Solar Physics, 2015. Online first

References in corpus (5)

• The Eruption from a Sigmoidal Solar Active Region on 2005 May 13
• Recurrent explosive eruptions and the sigmoid-to-arcade transformation in the sun driven by dynamical magnetic flux emergence
• The spectral evolution of impulsive solar X-ray flares. II.Comparison of observations with models
• Investigation of Hot X-ray Points (HXPs) Using Spectroheliograph Mg XII Experiment Data From CORONAS-F/SPIRIT
• Post-flare evolution of AR 10923 with Hinode/XRT

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• Thermal Trigger for Solar Flares III: Effect of the Oblique Layer Fragmentation
• Observations of the Current Sheet Heating in X-ray during a Solar Flare