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arXiv · 1407.0356

Fanning out of the $f$-mode in presence of nonuniform magnetic fields

Nishant K. Singh·Axel Brandenburg·Matthias Rheinhardt
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Abstract

We show that in the presence of a harmonically varying magnetic field the fundamental or $f$-mode in a stratified layer is altered in such a way that it fans out in the diagnostic $k\omega$ diagram, but with mode power also within the fan. In our simulations, the surface is defined by a temperature and density jump in a piecewise isothermal layer. Unlike our previous work (Singh et al. 2014) where a uniform magnetic field was considered, we employ here a nonuniform magnetic field together with hydromagnetic turbulence at length scales much smaller than those of the magnetic fields. The expansion of the $f$-mode is stronger for fields confined to the layer below the surface. In some of those cases, the $k\omega$ diagram also reveals a new class of low frequency vertical stripes at multiples of twice the horizontal wavenumber of the background magnetic field. We argue that the study of the $f$-mode expansion might be a new and sensitive tool to determining subsurface magnetic fields with longitudinal periodicity.

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Nishant K. Singh, Axel Brandenburg, Matthias Rheinhardt. 2014-07-01. Fanning out of the $f$-mode in presence of nonuniform magnetic fields. https://doi.org/10.1088/2041-8205/795/1/l8

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