Quantization of plasma density irregularities under the action of a powerful electromagnetic wave: The spectrum of upper hybrid oscillations self-consistently trapped in density cavities

Abstract

We present a theoretical model of the self-localization of the upper hybrid (UH) oscillations in plasma density depletions due to thermal nonlinearities driven by a homogeneous and monochromatic pump electric field. The Bohr-Sommerfeld condition for the trapped UH oscillations demands that the parameters of the density cavity be quantized. The depth and square of the depletion width across the magnetic field is proportional to an integer. The depth of the parabolically shaped cavity is proportional to the square of its width. The characteristic relative value of the density minimum is a few percent and the width is of the order of one meter for the pump wave amplitudes used in the ionospheric F-region experiments. We consider also the parametric decay of primary, localized UH oscillations trapped in the quantized plasma density depletions into secondary UH oscillations and lower-hybrid waves. We calculated the spectrum of the non-linear stabilized secondary UH oscillations which are also self-consistently trapped in the same density cavity. The spectrum of the UH oscillations is consistent with the observed spectrum of the downshifted (DM) and upshifted (UM) maximum in the stimulated electromagnetic emissions (SEE).