Multiple scattering of waves by a pair of gravitationally stratified flux tubes

TL;DR

This paper investigates how pairs of flux tubes in a stratified environment interact through near-field coupling, significantly affecting wave scattering properties and emphasizing the importance of multiple scattering effects in helioseismology.

Contribution

It demonstrates the impact of near-field jackets on flux tube scattering, revealing the dominant length scale and the stronger coupling of higher-beta flux tubes, advancing understanding of wave-flux tube interactions.

Findings

Near-field jackets significantly alter scattering coefficients and phases.

The dominant induction zone length is about half the incident wave's horizontal wavelength.

Higher-beta flux tubes exhibit stronger coupling due to near-field effects.

Abstract

We study the near-field coupling of a pair of flux tubes embedded in a gravitationally stratified environment. The mutual induction of the near-field {\it jackets} of the two flux tubes can considerably alter the scattering properties of the system, resulting in sizable changes in the magnitudes of scattering coefficients and bizarre trends in the phases. The dominant length scale governing the induction zone turns out to be approximately half the horizontal wave length of the incident mode, a result that fits in quite pleasantly with extant theories of scattering. Higher-$\beta$ flux tubes are more strongly coupled than weaker ones, a consequence of the greater role that the near-field jacket modes play in the such tubes. We also comment on the importance of incorporating the effects of multiple scattering when studying the effects of mode absorption in plage and interpreting related scattering measurements. That the near-field plays such an important role in the scattering process lends encouragement to the eventual goal of observationally resolving sub-wavelength features of flux tubes using techniques of helioseismology.