Resonant cyclotron emission of whistler waves by a modulated electron beam

The first observations of whistlers excited spontaneously by a modulated el ectron beam through normal Doppler shifted resonance have been reported in a laboratory experiment. The excited waves are propagating opposite to the beam direction and their phase and group velocities are characteristic of b eam-whistler resonant cyclotron coupling. These results should shed light o n mechanisms of whistler waves excitation in space plasmas, either by artif icial beams injected from spacecraft in the ionosphere and the magnetospher e or by fluxes of energetic particles present in many astrophysical and spa ce phenomena.