Near- and Far-Field Response to Compact Acoustic Sources in Stratified Convection Zones

TL;DR

This paper investigates how the acoustic continuum in the Sun's stratified interior affects surface wave observations, revealing that it masks compact sources and minimally contributes to observable seismic power.

Contribution

It demonstrates that the acoustic continuum creates a 'jacket' around sources, obscuring them and clarifying its limited role in surface seismic signals.

Findings

The acoustic continuum forms an 'acoustic jacket' around sources.

The continuum significantly masks the surface wave field from compact sources.

The continuum's contribution to observable inter-ridge seismic power is minimal.

Abstract

The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure -- the so-called `acoustic jacket' -- that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.