Photospheric high-frequency acoustic power excess in sunspot umbra: signature of magneto-acoustic modes

TL;DR

This study provides observational evidence of magneto-acoustic waves in sunspot umbrae through high-frequency acoustic power enhancements, supported by numerical modeling, suggesting a new diagnostic approach for magnetohelioseismology.

Contribution

The paper combines observational data and numerical simulations to identify magneto-acoustic waves in sunspots, advancing the understanding of wave behavior in magnetic solar regions.

Findings

Detection of high-frequency acoustic power excess in sunspot umbrae.

Identification of these waves as magneto-acoustic modes excited by sub-photospheric acoustic waves.

Potential development of a new diagnostic tool for magnetohelioseismology.

Abstract

We present observational evidence for the presence of MHD waves in the solar photosphere deduced from SOHO/MDI Dopplergram velocity observations. The magneto-acoustic perturbations are observed as acoustic power enhancement in the sunspot umbra at high-frequency bands in the velocity component perpendicular to the magnetic field. We use numerical modelling of wave propagation through localised non-uniform magnetic field concentration along with the same filtering procedure as applied to the observations to identify the observed waves. Guided by the results of the numerical simulations we classify the observed oscillations as magneto-acoustic waves excited by the trapped sub-photospheric acoustic waves. We consider the potential application of the presented method as a diagnostic tool for magnetohelioseismology.