Book Description

The report is concerned with the analysis of hydromagnetic waves which are generated in various regions of the magnetosphere and propagated to the earth in the extremely low frequency spectrum. Two different aspects of the problem are investigated, namely, propagation through inhomogeneous regions of the ionosphere and propagation and excitation of waves in current carrying regions of the ionosphere and the magnetosphere. Propagation through inhomogeneous regions is studied by two different methods: Transmission coefficients for hydromagnetic waves are obtained by assuming a linearly varying inhomogeneous region and by transforming the wave equation into a hypergeometric equation such that various types of inhomogeneities can be handled (Epstein theory). Assuming a hydromagnetic wave incident from above and propagating parallel to the earth's magnetic field, power transmission coefficients are calculated for various times of day. Propagation of hydromagnetic waves through a current carrying plasma is investigated on the basis of macroscopic equations in which additional terms arising from the presence of a constant current density are included. A general dispersion relation for small amplitude waves is derived. For propagation normal to the steady magnetic field, when the currents are normal to both, the direction of propagation and the static magnetic field, it is found that amplification takes place. For longitudinal propagation with currents in the transverse plane, the propagation constant remains unaffected. For longitudinal propagation, with currents also along the direction of propagation, the propagation constant has a resonance at the ion-cyclotron frequency for both, right and left hand polarization. (Author).