A generation mechanism for chorus emission

Authors: Trakhtengerts V Y

Publish Date: 1999/01/31

Volume: 17, Issue: 1, Pages: 95-100

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Abstract

Abstract A chorus generation mechanism is discussed which is based on interrelation of ELF/VLF noiselike and discrete emissions under the cyclotron waveparticle interactions A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause This process is accompanied by a steplike deformation of the energetic electron distribution function in the velocity space which is situated at the boundary between resonant and nonresonant particles The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator BWO regime of wave generation when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap in the form of a succession of discrete signals with growing frequency inside each element The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission when the strong wavelet starts from the equatorial plane The comparison is given of the model developed using some satellite and groundbased data In particular the appearance of separate groups of chorus signals with a duration 210 s can be connected with the preliminary stage of the step formation BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements Key words Magnetospheric physics Energetic particles · trapped Space plasma physics waveparticle interactions waves and instabilities

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