Magnetospheric VLF response to the atmospheric infrasonic waves Original Research Article

We consider the influence of atmospheric infrasonic waves on VLF whistler features in the Earth electron radiation belts. An infrasonic wave produces variations of plasma concentration in the ionosphere and VLF wave coefficient of reflection from the ionosphere. The coefficient of whistler reflection and its variation were calculated both analytically for simplified models and numerically for more realistic models of ionospheric altitude electron distributions. The frequency of infrasonic waves is close to the eigen-frequency of the wave - particle interaction processes in the radiation belts. Hence the magnetospheric resonator Q-factor modulation can switch the stationary VLF electromagnetic emission generation mode (hiss emissions) to a quasi-periodic or self-oscillation mode. The spatio-temporal processes in a disturbed magnetosphere were studied by an original code. The obtained results can explain the causes of the modulation of energetic electron precipitation fluxes and whistler wave intensity with a time scale of 10 to 100 sec in the morning and in the forenoon part of the radiation belts. Such periodical and quasiperiodical VLF emissions are often observed in the subauroral and auroral Earthʹs magnetosphere.