Properties of high-frequency wave power halos around active regions: an analysis of multi-height data from HMI and AIA onboard SDO

TL;DR

This study analyzes high-frequency wave power halos around active regions using multi-height data from SDO's HMI and AIA, revealing how magnetic field properties influence wave behavior and mode conversion processes.

Contribution

It provides detailed analysis of wave power maps at different heights and magnetic conditions, offering new insights into magneto-acoustic wave refraction and mode conversion mechanisms.

Findings

Power maps vary with wave frequency, magnetic inclination, and strength.

Signatures of wave refraction are observed at different observation heights.

Implications for p mode absorption and mode conversion theories are discussed.

Abstract

We study properties of waves of frequencies above the photospheric acoustic cut-off of $\approx$5.3 mHz, around four active regions, through spatial maps of their power estimated using data from Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The wavelength channels 1600 {\AA} and 1700 {\AA} from AIA are now known to capture clear oscillation signals due to helioseismic p modes as well as waves propagating up through to the chromosphere. Here we study in detail, in comparison with HMI Doppler data, properties of the power maps, especially the so called 'acoustic halos' seen around active regions, as a function of wave frequencies, inclination and strength of magnetic field (derived from the vector field observations by HMI) and observation height. We infer possible signatures of (magneto-)acoustic wave refraction from the observation height dependent changes, and hence due to changing magnetic strength and geometry, in the dependences of power maps on the photospheric magnetic quantities. We discuss the implications for theories of p mode absorption and mode conversions by the magnetic field.