Observations of Current Sheet Heating in X-Ray during a Solar Flare

Abstract

In the solar corona, magnetic reconnection occurs due to the finite resistivity of the plasma. At the same time, this resistivity leads to ohmic heating. Therefore, the reconnecting current sheet should heat the surrounding plasma. This paper presents experimental evidence of such plasma heating being caused by magnetic reconnection. We observed the effect during a C1.4 solar flare on 2003 February 16 at the active region NOAA 10278, near the solar limb. Thanks to such a location, we successfully identified all the principal elements of the flare: the flare arcade, the flux rope, and, most importantly, the presumed position of the current sheet. By analyzing the monochromatic X-ray images of the Sun obtained by the CORONAS-F/SPIRIT instrument in the Mg xii 8.42 Å spectral line, we detected a high-temperature (T ≥ 4 MK) emission at the predicted location of the current sheet. The high-temperature emission appeared during the CME’s impulsive acceleration phase. We believe that this additionally confirms that the plasma heating around the current sheet and the magnetic reconnection inside the current sheet are strongly connected.