Noémi Kinga Zsámberger, Robertus Erdélyi, and I have recently published a paper in The Astrophysical Journal analysing a further generalisation to the asymmetric slab waveguide model, now with an asymmetric magnetic field in the external plasma environment. We focus on potential application to oscillations of elongated magnetic bright points in inter-granular lanes, where even a small asymmetry in the parameters of the neighbouring granules could manifest itself as significant asymmetry in magneto-acoustic mode propagation. This analysis paves the way for development of magneto-seismology techniques that diagnose the magnetic field in structures where the magnetic field strength is traditionally difficult to directly measure. (Watch this space! We have upcoming research developing these magneto-seismology techniques in the works as I write this)
However, there is a caveat. We demonstrate that it is possible, at least in theory, for the magnetic and the plasma pressure gradient restoring forces to balance in such as way that a wave in an asymmetric waveguide can appear symmetric (i.e. the oscillations on each side of the slab are of equal amplitude). We call this deceptive type of wave "quasi-symmetric". The existence of quasi-symmetric waves means that we cannot assume waveguide symmetry even when we observe symmetric waves.
Access our open-access publication here.
Figure: An elongated magnetic bright point is considered as an asymmetric magnetic slab (Based on Liu et al. 2018).