Newly identified properties of surface acoustic power

TL;DR

This study investigates the properties of the acoustic halo around active regions, revealing correlations with magnetic field inclination and strength, and shifts in modal ridges, to better understand the phenomenon.

Contribution

It provides new insights into the relationship between magnetic field properties and enhanced acoustic power in the solar surface.

Findings

Enhanced high-frequency power correlates with magnetic-field inclination.

Maximum enhancement frequency increases with magnetic field strength.

Oscillations in halos show shifted modal ridges compared to quiet Sun.

Abstract

The cause of enhanced acoustic power surrounding active regions, the acoustic halo, is not as yet understood. We explore the properties of the enhanced acoustic power observed near disk center from 21 to 27 January 2002, including AR 9787. We find that (i) there exists a strong correlation of the enhanced high frequency power with magnetic-field inclination, with greater power in more horizontal fields, (ii) the frequency of the maximum enhancement increases along with magnetic field strength, and (iii) the oscillations contributing to the halos show modal ridges which are shifted to higher wavenumber at constant frequency in comparison to the ridges of modes in the quiet-Sun.