The collisions of high-velocity clouds with the galactic halo
  Spiral galaxies are surrounded by a widely distributed hot coronal gas and
seem to be fed by infalling clouds of neutral hydrogen gas with low metallicity
and high velocities. We numerically study plasma waves produced by the
collisions of these high-velocity clouds (HVCs) with the hot halo gas and with
the gaseous disk. In particular, we tackle two problems numerically: 1)
collisions of HVCs with the galactic halo gas and 2) the dispersion relations
to obtain the phase and group velocities of plasma waves from the equations of
plasma motion as well as further important physical characteristics such as
magnetic tension force, gas pressure, etc. The obtained results allow us to
understand the nature of MHD waves produced during the collisions in galactic
media and lead to the suggestion that these waves can heat the ambient halo
gas. These calculations are aiming at leading to a better understanding of
dynamics and interaction of HVCs with the galactic halo and of the importance
of MHD waves as a heating process of the halo gas.
