Abstract
Abstract. We have constructed a theory for the penetration of magnetosonic waves from the solar wind into the magnetosphere through a transition layer in a plane-stratified model for the medium. In this model the boundary layer is treated as a region, inside of which the parameters of the medium vary from values characteristic for the magnetosphere, to values typical of the solar wind. It is shown that if such a layer has sufficiently sharp boundaries, then magnetosonic eigen-oscillations can be excited inside of it. The boundaries of such a layer are partially permeable for magnetosonic waves. Therefore, if the eigen-oscillations are not sustained by an external source, they will be attenuated, because some of the energy is carried away by the oscillations that penetrate the solar wind and the magnetosphere. It is shown that about 40% of the energy flux of the waves incident on the transition layer in the magnetotail region penetrate to the magnetosphere’s interior. This energy flux suffices to sustain the stationary convection of magnetospheric plasma. The total energy input to the magnetosphere during a time interval of the order of the substorm growth phase time is comparable with the energetics of an average substorm.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions) – Space plasma physics (kinetic and MHD theory)
Highlights
The assumption that the solar wind MHD oscillations can play a significant role in the energetics of the Earth’s magnetosphere was made by Axford (1964)
We summarize the main results of this study: 1. We have determined the transmission and reflection coefficients of magnetosonic waves in solving the problem of their transmission from the solar wind to the magnetosphere through the transition layer
It has been shown that eigenmodes of magnetosonic oscillations exist in the transition layer, and they attenuate due to the escape of a portion of their energy to the solar wind and the magnetosphere
Summary
The assumption that the solar wind MHD oscillations can play a significant role in the energetics of the Earth’s magnetosphere was made by Axford (1964). When integrating the energy fluxes over the spectrum of magnetosonic waves incident on the magnetosphere from the solar wind, we allowed for the presence of “transparency windows” in regions of variations of their frequency and wave vector. 2, the model of the medium is described, and a matching of solutions of the MHD equations representing magnetosonic waves in the solar wind, the transition layer and the magnetosphere is performed. For the sake of simplicity assume that the velocity vector vi and the magnetic field vector Bi (i = I,II,III) are directed along the axis x This restricts the validity of our model of the medium to the region of the high-latitude boundary layer, which, occupies the main part of the surface of the nightside magnetosphere.
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