Hydromagnetic gravity waves in the solar atmosphere

We show that Alfven gravity waves propagating in a gravitationally stratifi ed atmosphere do not suffer damping as a result of the rate of working of t he gravity drift current on the electric field of the waves. A self-consist ent treatment involving conservation of total energy, Poynting's theorem, a nd the rate of working of the various drift currents on the electric field demonstrates that dissipation only arises from "real" dissipative processes such as ohmic heating or viscous effects; otherwise the system is adiabati c. We also outline the propagation properties of coupled small-amplitude hy dromagnetic gravity waves for the case of vertical and horizontal magnetic fields. In the latter case we discuss the phenomenon of critical level abso rption, which can take place where the horizontal wave phase speed matches the Alfven speed at some height in the atmosphere.