Hydromagnetic waves in a buoyant medium

Abstract

Lighthill has suggested that magnetic fields can transform gravity waves into Alfvén waves. The behaviour of gravity waves in an incompressible and infinitely conducting atmosphere is examined so as to check this suggestion. It is found that an upgoing gravity wave is converted to a downgoing Alfvén wave and that this conversion is affected without any introduced atmospheric discontinuity. In the ionosphere dissipation is sufficient, save at very long wavelengths, to inhibit mode conversion but in the solar atmosphere the process may well operate. The energy necessary to heat the solar corona could possibly be supplied by gravity waves when dissipation occurs after the conversion to an Alfvén wave.