Solar Magnetoseismology with Magnetoacoustic Surface Waves in Asymmetric Magnetic Slab Waveguides

Abstract

Solar magnetoseismology is an indirect method to approximate plasma parameters that are traditionally difficult to measure in the solar atmosphere using observations of magnetohydrodynamic waves. A magnetic slab can act as waveguide for magnetoacoustic waves that approximates magnetic structures in the solar atmosphere. The asymmetry of the slab caused by different plasma parameters in each external region affects both the eigenfrequencies and eigenfunctions differently at each side of the slab, that is, both the temporal and spatial profiles of the eigenmodes of propagation along the slab are influenced by the equilibrium asymmetry. We present two novel diagnostic tools for solar magnetoseismology that use this distortion to estimate the slab magnetic field strength using the spatial distribution of magnetoacoustic surface waves: the amplitude ratio and the minimum perturbation shift techniques. They have the potential to estimate background equilibrium parameters in inhomogeneous solar structures such as elongated magnetic bright points, prominences, and the clusters of magnetic brightenings rooted in sunspot light bridges known as light bridge surges or light walls, which may be locally approximated as slabs.