Cerenkov Excitation of WhistlerHelicon Waves by Ionospheric HF Heating

A novel scheme for exciting VLF waves and injecting them in the magnetosphere is presented. The scheme is based on Cerenkov excitation of whistler and helicon waves in an altitude range of 80-95 kin. Contrary to the traditional Cerenkov excitation which relies on a charge moving at speeds ex•g the local phase velocity of the wave, the present scheme relies on currents moving transversely to its flow direction. The moving current source is created by changing the spatial location of the energy deposition of an ionospheric heater in phase with the wave motion. Representative estimates of the VLF power injected in the magnetosphere are presented. tion (3) in time and the transverse spatial direction, and writE,.,t E• :3⁄4 iE•,, J,.,t J• q: iJ•y (4)