An explanation of triggered very‐low‐frequency emissions

A mechanism is proposed for the generation of vlf waves in the earth's vicinity. It is assumed that the waves are produced by resonance interactions between waves propagating in a plasma and energetic charged particles trapped in the geomagnetic field. It is postulated that the high intensities of vlf radiation that are observed, as contrasted with intensities expected from the low radiation yield of the resonance interaction and a reasonable particle density, require the existence of coherence in the radiation. This coherent radiation is proposed to be produced by organization of the relative phases of the helical orbits of the geomagnetically trapped particles. The mechanism proposed makes use of the cyclotron resonance between the plasma waves and the particles. (T.F.H.)