AN ELECTROMAGNETIC-FIELD, INDUCED IN THE IONOSPHERE AND ATMOSPHERE AND ON THE EARTHS SURFACE BY LOW-FREQUENCY ALFVEN OSCILLATIONS OF THE MAGNETOSPHERE - GENERAL-THEORY

Within the framework of a model of the near-terrestrial environment which represents adequately its vertical stratification, an analytical study is made of the structure of an electromagnetic field induced in the near-terrestrial layers by low-frequency Alfven oscillations of the magnetosphere (whose frequency is much lower than the ionospheric eigenfrequencies). We begin this study by solving the problem for monochromatic oscillations which have a given horizontal wave vector, with an arbitrary orientation with respect to the meridian (the geomagnetic field being oblique). On the basis of this solution, using an inverse Fourier transform we derive general formulae to express the electromagnetic oscillation field on the Earth's surface in terms of the electromagnetic field of an Alfven wave on the lower boundary of the magnetosphere. A boundary condition for Alfven waves at the ionosphere-magnetosphere interface is obtained as an independent result. This condition carries all information on the ionosphere and on lowerlying layers, needed to solve problems of Alfven oscillations of the magnetosphere.