Seismology of the Wounded Sun

TL;DR

This paper investigates how magnetic active regions on the Sun affect seismic wave propagation, revealing significant travel time perturbations caused by wave interactions with magnetic fields, which could lead to new directional seismology methods.

Contribution

It introduces a numerical simulation approach to quantify wave energy losses and travel time changes caused by magnetic fields in active regions, highlighting their impact on surface seismology.

Findings

Travel time perturbations can exceed 40 seconds in 1 kG magnetic fields.

Waves leaving and re-entering the interior influence surface seismology signatures.

Wave orientation relative to magnetic fields affects travel times.

Abstract

Active regions are open wounds in the Sun's surface. Seismic oscillations from the interior pass through them into the atmosphere, changing their nature in the process to fast and slow magneto-acoustic waves. The fast waves then partially reflect and partially mode convert to upgoing and downgoing Alfv\'en waves. The reflected fast and downgoing Alfv\'en waves then re-enter the interior through the active regions that spawned them, infecting the surface seismology with signatures of the atmosphere. Using numerical simulations of waves in uniform magnetic fields, we calculate the upward acoustic and Alfv\'enic losses in the atmosphere as functions of field inclination and wave orientation as well as the Time-Distance `travel time' perturbations, and show that they are related. Travel time perturbations relative to quiet Sun can exceed 40 seconds in 1 kG magnetic field. It is concluded that active region seismology is indeed significantly infected by waves leaving and re-entering the interior through magnetic wounds, with differing travel times depending on the orientation of the wave vector relative to the magnetic field. This presages a new directional-time-distance seismology.