Evidence of increasing acoustic emissivity at high frequency with solar cycle 23 in Sun-as-a-star observations

TL;DR

This study analyzes Sun-as-a-star data from SOHO to observe increased high-frequency acoustic emissivity during solar cycle 23, suggesting mode conversion as a possible explanation and potential applications to stellar magnetic activity studies.

Contribution

It provides the first evidence of increased high-frequency acoustic emissivity during a solar cycle using Sun-as-a-star observations, highlighting mode conversion as a key mechanism.

Findings

18+-3 enhancement in velocity observations

3+-2 enhancement in intensity observations

Mode conversion explains velocity enhancement

Abstract

We used long high-quality unresolved (Sun-as-a-star observations) data collected by GOLF and VIRGO instruments on board the ESA/NASA SOHO satellite to investigate the amplitude variation with solar cycle 23 in the high-frequency band (5.7 < nu< 6.3 mHz). We found an enhancement of acoustic emissivity over the ascending phase of about 18+-3 in velocity observations and a slight enhancement of 3+-2 in intensity. Mode conversion from fast acoustic to fast magneto-acoustic waves could explain the enhancement in velocity observations. These findings open up the possibility to apply the same technique to stellar intensity data, in order to investigate stellar-magnetic activity.