Coherent generation of the terrestrial kilometric radiation by non-linear beatings between electrostatic waves

A. Roux (1) , R. Pellat (2)

1 CRPE - Centre de recherches en physique de l'environnement terrestre et planétaire
2 CPHT - Centre de Physique Théorique [Palaiseau]

The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma is studied analytically. These waves, which are driven unstable by auroral beams of electrons, are shown to suffer a further geometrical amplification while they propagate towards resonances. Simultaneously their group velocities tend to be aligned with the geomagnetic field. Then it is shown that the electrostatic energy tends to accumulate at, or near wLH and v\m, the local lower and upper hybrid frequencies. Due to this process, large amplitude electrostatic waves with very narrow spectra should be observed near these frequencies at any place along the auroral field lines where intense beam driven in- stability takes place. These intense quasi-monochromaticelectrostatic waves are then shown to give rise by a coherent- non-linear three wave process to an intense electromagnetic radiation. Depending upon the ratio ou /uu between the electron plasma frequency and the electron gyrofrequency the electromagnetic wave can be radiated in the ordinary mode ( at wUH) ) or in the extraordinary mode( at 2wUH) - As far as the ratio wpe/wce tends to be rather small it is shown that the most intense radiation should be observed at 2wUH in the extraordinary mode.

Domaines: Sciences de la Terre

A. Roux, R. Pellat. Coherent generation of the terrestrial kilometric radiation by non-linear beatings between electrostatic waves. [Research Report] Note technique CRPE n° 56, Centre de recherches en physique de l'environnement terrestre et planétaire (CRPE). 1979, 35 p. ⟨hal-02191404⟩