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Observations revealed that various kinds of oscillations are excited in solarflare regions. Quasi-periodic pulsations (QPPs) in the flare emissions arecommonly observed in a wide range of wavelengths. Recent observations havefound that fast-mode magnetohydrodynamic (MHD) waves are quasi-periodicallyemitted from some flaring sites (quasi-periodic propagating fast-modemagnetoacoustic waves; QPFs). Both of QPPs and QPFs imply a cyclic disturbanceoriginating from the flaring sites. However, the physical mechanisms remainpuzzling. By performing a set of two-dimensional MHD simulations of a solarflare, we discovered the local oscillation above the loops filled withevaporated plasma (above-the-loop-top region) and the generation of QPFs fromsuch oscillating regions. Unlike all previous models for QPFs, our modelincludes essential physics for solar flares, such as magnetic reconnection,heat conduction, and chromospheric evaporation. We revealed that QPFs can bespontaneously excited by the above-the-loop-top oscillation. It was found thatthis oscillation is controlled by the backflow of the reconnection outflow. Thenew model revealed that flare loops and the above-the-loop-top region are fullof shocks and waves, which is different from the previous expectations based ona standard flare model and previous simulations. In this paper, we will showthe QPF generation process based on our new picture of flare loops and willbriefly discuss a possible relationship between QPFs and QPPs. Our findingswill change the current view of solar flares to a new view in which they are avery dynamic phenomenon with full of shocks and waves.

Above-the-loop-top Oscillation and Quasi-periodic Coronal Wave Generation in Solar Flares