Thermal Evolution of Plasmoids in Current Sheet of a Solar Flare

Solar flares are phenomena that magnetic energy is converted to heat and electromagnetic wave in the corona by magnetic reconnection. It is considered that the formation and ejection of the plasma blobs (plasmoids) in a current sheet makes the magnetic reconnection in solar flares faster. Since plasmas in the reconnection region are heated in a process of magnetic reconnection, revealing the thermal structure of the plasmoids and its temporal change may contribute for understanding the process of the fast magnetic reconnection. We have analyzed the 2010 August 18 flare, which produced multiple plasmoids in a current sheet (Takasao et al. 2012). The differential emission measure (DEM) of the plasmoids was reported under the assumption of the DEM of a single gaussian shape with a characteristic temperature (Kumar & Cho 2013). We have used the Cheung’s DEM code (Cheung et al. 2015), which approximates the DEM by a sum of a limited small number of multiple gaussian components. We report a few plasmoids here, two plasmoids in a coalescing process and the other plasmoid ejected from the current sheet. The DEM of the plasmoids as a whole had the largest peak at around 8-12 MK and some local maxima at lower temperatures. We have observed the heating of plasmoids in both the coalescence and the ejection. While the largest peak was shifted to a higher temperature in the DEM of the coalesced plasmoid, a part of the emission measure at low temperature shifted to higher temperature in the DEM of the ejected plasmoid. We will also report thermal structures within the plasmoid.