Effect of the ionosphere on the propagation of MHD wave beams

A theoretical study is made of the propagation of electromagnetic waves along the earth's surface excited by an MHD wave beam of magnetospheric origin. It is assumed that such magnetospheric signals have been subject to the effects of ionospheric screening and transformation. Expressions are obtained for fields at large distances from the source, and it is shown that, at sufficiently large distances, the wave moves along the earth's surface with an Alfven velocity. It is noted that a correlation of geomagnetic variations on the earth's surface and magnetospheric oscillations has demonstrated the suitability of such diagnostics for purposes of ground-based diagnostics.