Fanning out of the f-mode in presence of nonuniform magnetic fields
Nordita Astrophysics seminars
Wednesday 17 September 2014
to 14:15 at
Nishant Singh (Nordita)
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.