Speaker
Nishant Singh
(Nordita)
Description
We show that in the presence of a magnetic field that is
varying harmonically in space, 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, 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, here we employ 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 azimuthal or other
horizontal periodicity. Some preliminary results from the
analysis of HMI data will also be presented.
Primary author
Nishant Singh
(Nordita)
