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Fanning out of the f-mode in presence of nonuniform magnetic fields
  Nordita Astrophysics seminars

Wednesday 17 September 2014
from 13:30 to 14:15
at 122:026
Speaker : Nishant Singh (Nordita)
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.

arXiv:1407.0356

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