Bochum 2002 – wissenschaftliches Programm
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P: Plasmaphysik
P 18: Astrophysikalische und extraterrestrische Plasmen
P 18.3: Vortrag
Mittwoch, 20. März 2002, 17:10–17:25, HZO 70
Nonlinear coherent interaction of Farley-Buneman waves in the auroral ionosphere — •Claudia-Veronika Meister1 and Alexandra Volosevich2 — 1Space Plasma Physics, Potsdam, Germany — 2State University. Mogilev, Belarus
According to a widespread point of view, intensive electrostatic structures in the E-region of the auroral ionosphere can be a consequence of the excitation of Farley-Buneman (FB) plasma instabilities. But in spite of the successes of the theoretical and experimental research of the auroral radar scattering, it is impossible to explain the existence of auroral echoes with large aspect angles, the wave propagation perpendicular to the electron drift velocity and wave scales less than one meter.
In this paper the coherent nonlinear interaction of three and four electrostatic FB waves are considered analytically and numerically. The evolution of the waves is described by a system of magnetohydrodynamic equations. It is shown that the interaction of the coherent waves is the main physical mechanism which leads to the saturation of the FB-instability. If waves with linearly increasing amplitudes exist, the wave interaction causes the generation of waves propagating perpendicularly to the electron drift. In the case that the previously linear waves have wavelengths of the order of 1-5 m, in the auroral plasma, the amplitudes of the density waves beyond the linear region of evolution are found to be of the order of 2-6 % of the mean density. The amplitudes of the nonlinear waves increase with increasing wavelength of the plasma disturbances and with growing electron drift velocity.