Scattering of acoustic waves by a magnetic cylinder

TL;DR

This paper investigates how acoustic waves scatter off a magnetic cylinder using the Born approximation, validating its accuracy for certain conditions and highlighting its limitations at small scales.

Contribution

It applies the first-order Born approximation to model acoustic wave scattering by magnetic cylinders and compares results with exact solutions to establish validity.

Findings

Born approximation accurately predicts travel-time shifts for magnetic to gas pressure ratios up to first order.

The approximation remains valid for finite cylinder radii but fails as the radius approaches zero.

The study enhances understanding of magnetic effects in helioseismology.

Abstract

With the aim of studying magnetic effects in time-distance helioseismology, we use the first-order Born approximation to compute the scattering of acoustic plane waves by a magnetic cylinder embedded in a uniform medium. We show, by comparison with the exact solution, that the travel-time shifts computed in the Born approximation are everywhere valid to first order in the ratio of the magnetic to the gas pressures. We also show that, for arbitrary magnetic field strength, the Born approximation is not valid in the limit where the radius of the magnetic cylinder tends to zero.