%0 Journal Article
%T Fanning out of the $f$-mode in presence of nonuniform magnetic fields
%A Nishant K. Singh
%A Axel Brandenburg
%A Matthias Rheinhardt
%J Physics
%D 2014
%I arXiv
%R 10.1088/2041-8205/795/1/L8
%X 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.
%U http://arxiv.org/abs/1407.0356v1