Sunspot seismic halos generated by fast MHD wave refraction

TL;DR

This paper proposes a model explaining seismic halos around sunspots as resulting from fast MHD wave refraction, supported by numerical simulations, offering insights into the high-frequency power excess observed in active regions.

Contribution

It introduces a novel explanation for seismic halos based on fast mode wave refraction, supported by numerical simulations and predictive capabilities.

Findings

Qualitative explanation of halo magnitude

Prediction of halo behavior in future observations

Support for fast MHD wave refraction as the cause

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.