Abstract
The nonlinear ionospheric effects of very low-frequency (VLF) electromagnetic radiation produced by lightning discharges are considered. Electric and magnetic field measurements by a rocket in the ionosphere reported by Kelly et al. [Geophys. Res. Lett. 17, 2221 (1990)] show the simultaneous presence of powerful electromagnetic whistler wave bursts along with electrostatic waves and a magnetic pulse with duration about 20 ms. The parametric decay of whistler mode waves into electrostatic waves and ultralow-frequency (ULF) electromagnetic waves is proposed as a possible explanation for the observed phenomenon. The evolution of whistler mode wave decay instabilities in time and two spatial dimensions is studied. The nonlinear dispersion equation is obtained, and solved numerically. Two-fluid magnetohydrodynamics is used to describe the three-wave interaction. The theoretical results are compared with observational data.
Published Version
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