Sunspot seismic halos generated by fast MHD wave refraction

Astronomy and Astrophysics (Impact Factor: 5.08). 05/2009; DOI: 10.1051/0004-6361/200913030
Source: arXiv

ABSTRACT We suggest an explanation for the high-frequency power excess surrounding active regions known as seismic halos. The idea is based on numerical simulations of magneto-acoustic waves propagation in sunspots. We propose that such an excess can be caused by the additional energy injected by fast mode waves refracted in the higher atmosphere due to the rapid increase of the Alfven speed. Our model qualitatively explains the magnitude of the halo and allows to make some predictions of its behavior that can be checked in future observations. Comment: Accepted by Astronomy and Astrophysics Letters

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