Modeling of the electromagnetic ion cyclotron wave generation in the H+–He+ plasma of the inner magnetosphere

•We calculate the integrated gain of EMIC waves in the H+–He+ plasma.•The integrated wave gain increases with L-shell increase.•The integrated wave gain reaches maximum in the afternoon sector.•The local growth rate can reach maximum outside the equator at latitudes within ±10°.•Our results are in agreement with the results of EMIC wave satellite observations.

Behaviors of the integrated wave gain of electromagnetic ion cyclotron (EMIC) waves in the H+–He+ plasma of the inner magnetosphere is investigated. The integrated wave gain is obtained by integration of a temporal local growth rate along a geomagnetic field line. The local growth rate is determined by the method of Kennel and Petschek (1966) generalized on the case of a bi-ion plasma. The concentration of the cold plasma is obtained on a basis of an empirical model of the plasmasphere and trough by Sheeley et al. (2001). The energetic proton flux in the equatorial inner magnetosphere is set by the empirical model of Milillo et al. (2001), which refers to the conditions of low geomagnetic activity. The coefficients of EMIC wave reflection from the conjugated ionosphere are calculated using the International Reference Ionosphere (IRI) model. It is shown that the integrated wave gain of the EMIC waves increases with L-shell increasing and peaks around 14–20 MLT. In the afternoon sector the integrated wave gain reaches maximum in the cold plasma of higher density. Here the EMIC waves with the frequency below the equatorial He+ gyrofrequency will be generated. The main findings of our study are in agreement with the basic experimental results on the EMIC wave occurrence in the equatorial middle magnetosphere known from satellite observations.