Subphotospheric Resonator and Local Oscillations in Sunspots

Abstract

The conditions under which the subphotospheric slow-wave resonator can be responsible for the local oscillations in a sunspot have been determined. A rich spectrum of local 3-min oscillations can be produced by the subphotospheric resonator only if the magnetic field in the resonator magnetic flux tube is much weaker than the surrounding sunspot magnetic field. Convective upflows of hot plasma in the sunspot magnetic field satisfy this condition. Consequently, there must be a correlation between the local oscillations and umbral dots, because the latter are produced by convective flows. Various modes of operation of the subphotospheric resonator give rise to wave packets of 3-min oscillations and umbral flashes. It is shown that giant local umbral flashes can emerge under certain conditions for the excitation of oscillations in the subphotospheric resonator.