TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 6), pp. 451-458, 2012

Possibility of magnetospheric VLF response to atmospheric infrasonic waves

P. A. Bespalov1 and O. N. Savina2,3

1Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St, 603950 Nizhny Novgorod, Russia
2State University the Higher Scool of Economics, 25/12 B. Pecherskaya St, 603155 Nizhny Novgorod, Russia
3State Technical University, 24 Minina St, 603600 Nizhny Novgorod, Russia

(Received May 31, 2010; Revised March 24, 2011; Accepted May 6, 2011; Online published July 27, 2012)

Abstract: In this paper, we consider a model of the influence of atmospheric infrasonic waves on VLF magnetospheric whistler wave excitation. This excitation occurs as a result of a succession of processes: a modulation of the plasma density by acoustic-gravity waves in the ionosphere, a reflection of the whistlers by ionosphere modulation, and a modification of whistler wave generation in the magnetospheric resonator. A variation of the magnetospheric resonator Q-factor has an influence on the operation of the plasma magnetospheric maser, where the active substances are radiation belt particles, and the working modes are electromagnetic whistler waves. The magnetospheric maser is an oscillating system which can be responsible for the excitation of self-oscillations. These self-oscillations are frequently characterized by alternating stages of accumulation and precipitation of energetic particles into the ionosphere during a pulse of whistler emissions. Numerical and analytical investigations of the response of self-oscillations to harmonic oscillations of the whistler reflection coefficient shows that even a small modulation rate can significantly change magnetospheric VLF emissions. Our results can explain the causes of the modulation of energetic electron fluxes and whistler wave intensity with a time scale from 10 to 150 s in the day-side magnetosphere. Such quasi-periodic VLF emissions are often observed in the sub-auroral and auroral magnetosphere and have a noticeable effect on the formation of space weather phenomena.
Key words: Magnetosphere-ionosphere interactions, wave propagation, wave-particle interactions.

Corresponding author E-mail: pbespalov@mail.ru

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