Whistler generation by an ion beam limited in the transverse direction

Interaction of spacely limited beam of heavy energy ions with ionospheric plasma under conditions typical for the active experiments conducted in the space when the development of ion-ion beam instability at Cherenkov resonance of VLF-waves with ions is the main process, is studied theoretically. Electrostatic waves with frequencies near and over low-hybrid frequency are excited most efficiently. The instability threshold is determined mainly by two processes: wave carrying away from interaction range with a beam and their Landau damping at background plasma electrons. Type of distribution function of heated electrons is determined using quasi-linear theory and it enables to determine energy spectrum of VLF-waves with maximum near low-hybrid frequency and decreasing gradually with frequency growth. The spectrum maximum position is determined by nonlinear processes of the induced scattering at ions. 4 refs