Signatures of Emerging Subsurface Structures in Acoustic Power Maps

TL;DR

This paper demonstrates that subsurface structures in the Sun can be detected by analyzing changes in acoustic power maps, potentially allowing early identification of emerging active regions before surface signs appear.

Contribution

It introduces a method using acoustic power maps derived from simulations and SOHO/MDI observations to detect subsurface structures indicative of emerging solar active regions.

Findings

Simulations show acoustic power is sensitive to subsurface wave speed perturbations.

Acoustic power variations can precede visible surface emergence.

Potential for early prediction of active region formation.

Abstract

We show that under certain conditions, subsurface structures in the solar interior can alter the average acoustic power observed at the photosphere above them. By using numerical simulations of wave propagation, we show that this effect is large enough for it to be potentially used for detecting emerging active regions before they appear on the surface. In our simulations, simplified subsurface structures are modeled as regions with enhanced or reduced acoustic wave speed. We investigate the dependence of the acoustic power above a subsurface region on the sign, depth, and strength of the wave speed perturbation. Observations from the Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) prior and during the emergence of NOAA active region 10488 are used to test the use of acoustic power as a potential precursor of magnetic flux emergence.