Current driven electrostatic ion cyclotron waves in presence of parallel electric field in the magnetosphere

Electrostatic ion cyclotron (EIC) waves driven by the electron currents and ions beams at frequencies near the harmonics of the ion cyclotron have been a common feature of the auroral magnetospheric plasma as observed by satellite. In the generation mechanism of EIC waves, the resonance excitation of the beam-ion-cyclotron modes by the target ions has been considered. The counterstreaming of electrons and ion beams along auroral magnetic field line in the region above parallel electric field has been dealt earlier. In the present paper the growth rate of EIC waves has been derived from linear dispersion relation for low frequency electrostatic waves in an anisotropic warm magnetized plasma consisting of beam ions, target ions and drifting bulk electrons in the region of weak parallel electric field. Finding of the theoretical investigations of growth rate are used to explain the excitation mechanism of EIC waves in the extremely low frequency range (ELF) range as observed by satellites in the auroral region of the magnetosphere. (author). 25 refs., 5 figs