European Solar Physics Online Seminar Archive

While surface waves propagating at tangential discontinuities have been studied in great detail, few studies have been dedicated to the investigation of the nature of waves at contact discontinuities, i.e. plasma discontinuity, where the background magnetic field crosses the interface between two media. In this talk, I will show that by introducing magnetic field inclination, the frequency of waves is rendered complex, where the imaginary part describes wave attenuation, due to lateral energy leakage. We investigate the eigenvalue and initial value problem and determine the conditions of transition from contact with the tangential discontinuity. Finally, I will present an investigation into the effect of magnetic field inclination on magnetic Rayleigh-Taylor instability. [more]

Are solar MHD waveguides symmetric? It is convenient to assume that they are. The solar physics community is familiar with the traditional notion of sausage and kink waves, which propagate along waveguides in the solar atmosphere that we assume are symmetric. In this talk, we drop this assumption and motivate the study of MHD wave propagation in asymmetric waveguides from theoretical and observational viewpoints. We discuss the implications that asymmetric waveguides have for mode identification, highlighting the observational ambiguity between waves in symmetric and asymmetric waveguides, which becomes a crucial consideration when implementing magneto-seismology diagnostics. We present a novel technique for solar magneto-seismology that utilises the observed asymmetry of MHD waves to diagnose background parameters of the solar atmosphere that are difficult to measure using traditional methods. We present a preliminary application of this technique to chromospheric fibrils as a proof-of-concept and discuss the potential further application to prominences, elongated magnetic bright points, and sunspot light walls. [more]

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