Analysis of High-Resolution Observations of Sunspot Oscillations and Waves

Abstract:

Oscillations of sunspots with a characteristic period of 3 minutes are prominent
features of the sunspot dynamics. In the sunspot chromosphere, the oscillations are
observed in the form of "running penumbral waves" representing shocks with narrow
compression fronts, traveling along the expanding magnetic field lines. The origin
of the sunspot oscillations and waves is not understood, and is a subject of hot
debates. It had been suggested that the sunspot oscillations may be due to leakage
of high-frequency acoustic (p) modes excited in subphotospheric layers. An
alternative point of view is that the sources of sunspot oscillations and waves are
in the chromosphere. Using long series of high-resolution sunspot images obtained
with a narrow-band H-alpha filter at the 1.6m New Solar Telescope at Big Bear Solar
Observatory, I identify individual wave excitation events, investigate their
properties and discuss potential physical mechanisms.