Time-Distance analysis of the Emerging Active Region NOAA 10790

TL;DR

This study uses time-distance helioseismology to analyze the emergence of Active Region NOAA 10790, revealing subsurface sound speed variations and estimating the flux emergence speed, enhancing understanding of solar magnetic activity.

Contribution

It provides new insights into the subsurface dynamics of active region emergence and estimates the flux emergence speed using helioseismic data.

Findings

Shallow regions of increased sound speed correlate with magnetic activity.

Deeper regions of increased sound speed are observed at sunspot pores.

Emerging magnetic flux has an estimated speed of around 1 km/s.

Abstract

We investigate the emergence of Active Region NOAA 10790 by means of time--distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the region of the flux emergence, possibly relating to a temperature perturbation due to magnetic quenching of eddy diffusivity, or to a dense flux tube. We detect and track an object in the subsurface layers of the Sun characterised by increased sound speed which could be related to emerging magnetic flux and thus obtain a provisional estimate of the speed of emergence of around $1 {\rm km s^{-1}}$.