Magnetoacoustic cutoff effect in numerical simulations of the partially ionized solar atmosphere.

The cutoff effect is a significant determinant of solar magnetohydrodynamic wave propagation and hence pivotal in energy transfer studies, such as solar plasma heating and seismological diagnostics. Despite continuous efforts, no good agreement between observed waveperiods and theory or numerical simulations was found. Our objective is to investigate the magnetoacoustic cutoff effect in the partially ionized solar atmosphere, factoring in the two-fluid effects.

Transverse oscillations and an energy source in a strongly magnetized sunspot.

The solar corona is two to three orders of magnitude hotter than the underlying photosphere, and the energy loss of coronal plasma is extremely strong, requiring a heating flux of over 1,000 W m to maintain its high temperature. Using the 1.6 m Goode Solar Telescope, we report a detection of ubiquitous and persistent transverse waves in umbral fibrils in the chromosphere of a strongly magnetized sunspot.