Effects of hydromagnetic waves in the magnetosphere



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The effects on the plasma trapped in the earth's magnetosphere by hydromagnetic waves propagating in the magnetosonic mode are considered in this paper. First, local particle heating due to an energy exchange between particles and waves known as magnetic Landau (transit-time) damping is investigated. Heating of both thermal particles and proton fluxes is considered. While thermal protons receive little energy from such a mechanism, a large quantity of energy of the order of lO[raised 16] to 10[raised 18] ergs per sec within a volume of 10 earth radii can be supplied to the thermal electrons. The heating of nonthermal, fast proton fluxes is also calculated and are found to receive by magnetic Landau damping an energy per unit volume which is two orders of magnitude higher than the heating for thermal electrons. The proton fluxes, however receive a power input two-orders of magnitude higher than the thermal electrons. The energy input to the protons is found to be able to penetrate deeply into the magnetosphere and to be sufficient to sustain a diamagnetic ring current which is believed to be responsible for large geomagnetic storms. The exchange of momentum between the waves and particles is considered In the second parb of the paper. By not discarding the imaginary part of Maxwell's equations in reduced form, the elkonal equation is shown to be true for all frequencies and wavelengths. A divergenceless wave momentum density is constructed from vzhich a radiation pressure tensor is formed. This tensor is then added to the magnetic field tensor and kinetic pressure tensor in the magnetosphere in order to calculate the effect on the earth's magnetic field. It is found that the field at the earth will vary by several gamma (1 [delta] = 10[raised -5] gauss) in magnitude due to the exchange of momentum between particles and hydromagnetic waves.