Magnetohydrodynamic wave propagation from a localized source including hall effect

Abstract

Lighthill’s theorem on magnetohydrodynamic wave propagation from a localized source gives an asymptotic expression for the wave amplitude at large distance from the source and this theorem is applied to a laboratory plasma. Attention is focused mainly on conditions where the Alfven speed is large compared with the sound speed and where the wave frequency is of the same order as the ion cyclotron frequency. These conditions are also typical of certain natural plasmas. The manner in which the wave amplitude depends on the direction of propagation and on the ratio of the wave frequency to the ion cyclotron frequency is examined and illustrated by graphs which also cover a range of source sizes. An extension is made into a two-fluid theory such that electron inertia and electron source terms can be included and the effect of finite electrical conductivity is considered.