Larisa Kashapova, On energy release during the “flat” gradual phase of faint solar flares.
Dr Larisa Kashapova (Institute for Solar-Terrestrial Physics of SB RAS, Irkutsk, Russia)
We present results of study and discussion of problems concerning the processes of the energy release and transport during gradual phases of solar flares. The most well-known object of gradual phase investigation is long-duration events (LDEs). They are characterized by emission of the anomalously long-lived hot coronal plasma during several hours after the impulse phase. Observed phenomena could be either a result of a significant suppression of the thermal conductivity or a continuous energy input. Also, it could be a combination of both mechanisms. We found two C-class flares that showed an extraordinary long flat emission in the X-ray flux curves in the 3-12 keV energy band. The "flat emission" period was also observed at EUV and microwaves. The quasi-periodic pulsations were detected in the evolution of the electron temperature. Analysis of the oscillations in microwave and ultraviolet emission during the 7 June 2012 flare supports hypothesis that the wave energy, coming from the sunspot to the flare site, can keep up the plasma emission by suppressing the plasma thermal conductivity. The preliminary analysis of the 21 July 2013 flare are presented. The results of both analyses are discussed from the point of view of different mechanisms explaining LDEs and the role of wave energy in them.