Signatures of emerging subsurface structures in the sun

TL;DR

This study explores whether acoustic power observations can detect subsurface structures indicative of emerging active regions on the sun before they become visible on the surface, using simulations and real data analysis.

Contribution

It demonstrates how acoustic power variations relate to subsurface wavespeed perturbations, advancing methods for early detection of solar active regions.

Findings

Acoustic power depends on wavespeed perturbation sign, depth, and strength.

Simulations show detectable acoustic signatures of subsurface structures.

Analysis of SOHO/MDI data supports simulation results.

Abstract

The complex dynamics that lead to the emergence of active regions on the sun are poorly understood. One possibility is that magnetic structures (flux tubes, etc.) rise from below the surface by self induction and convection that lead to the formation of active regions and sunspots on the solar surface. For space weather forecasting, one would like to detect the subsurface structures before they reach the surface. The goal of this study is to investigate whether sound speed perturbations associated with subsurface structures could affect the acoustic power observed at the solar surface above them. Possible mechanisms for this effect are wave reflection, scattering or diffraction. By using numerical simulations of wave propagation in the solar interior, we investigate whether observations of the acoustic power can be used to detect emerging active regions before they appear on the surface. In the simulations, subsurface structures are modeled as regions with enhanced or reduced acoustic wavespeed. We show how the acoustic power above a subsurface region depends on the sign, depth and strength of the wavespeed perturbation. For comparison, we analyze observations from SOHO/MDI of the emergence of solar active region NOAA 10488.