Analysis of Time-Distance Helioseismology for Detection of Emerging Active Regions

TL;DR

This study evaluates the effectiveness of time-distance helioseismology in detecting emerging active regions by analyzing numerical models and solar observations, highlighting its potential for early detection of solar activity.

Contribution

It applies and assesses a helioseismic technique on models and real data, exploring its spatial resolution, accuracy, and ability to identify pre-emergence signatures of active regions.

Findings

Strong pre-emergence phase travel time shifts detected in 3 of 5 active regions

Technique shows potential for early detection of flux emergence

Discussion on noise and criteria for true positive detections

Abstract

A time-distance helioseismic technique, similar to the one used by Ilonidis et al (2011), is applied to two independent numerical models of subsurface sound-speed perturbations to determine the spatial resolution and accuracy of phase travel time shift measurements. The technique is also used to examine pre-emergence signatures of several active regions observed by the Michelson Doppler Imager (MDI) and the Helioseismic Magnetic Imager (HMI). In the context of similar measurements of quiet sun regions, three of the five studied active regions show strong phase travel time shifts several hours prior to emergence. These results form the basis of a discussion of noise in the derived phase travel time maps and possible criteria to distinguish between true and false positive detection of emerging flux.