The Atypical Sunquake of May 10, 2012, and Specifics of Nonstationary Processes in the Active Region with a Magnetic Field of Composite Topology.

The M flare that arises after magnetic field emersion in a small spot is analyzed. The disturbance, which propagated downwards and generated a source of acoustic waves (sunquake), was simultaneous with an outburst of hard X-radiation. The reasons of such sunquakes are discussed. Rearrangement of the magnetic configuration in the analyzed event is confirmed: field lines and strong currents at low altitudes above the polarity boundary line are transformed into the currents along the system of loops oriented at wide angles to the neutral line. This rearrangement occurred in the proximity of a small region (sigmoid) presumably identified by the location of the primary pulse energy release. In this case, there was no development of a high-energy sigmoid flare with the formation and ejection of large-scale magnetized ropes. Apparently, this was hindered by the nonstationarity of the phenomena at this activity center with a magnetic field of composite topology and multiple flare-generating centers. [ABSTRACT FROM AUTHOR]