Alfven Waves in a Gravitational Field with Flows

A. Satya Narayanan, C. Kathiravan, R. Ramesh

Indian Institute of Astrophysics, Bangalore -560 034, India

The gravitational stratification effect on magnetohydrodynamic waves at a single interface in the solar atmosphere has been studied in the penumbral region of the sunspot recently. The existence of slow and fast magneto acoustic gravity waves and their characteristics has been discussed. The effect of flows on magneto acoustic gravity surface waves leads to modes called flow modes or v-modes. The present geometry is that of a plasma slab moving with uniform velocity surrounded by neutral gas. A critical width of the slab has been identified for both the surface modes at which the phase velocity is the same as with different density ratios. The dispersion characteristics change significantly with a change in the value of G (gravity).