Features of Generation of Quasi-Periodic VLF Emissions with Significant Frequency Dynamics Inside the Plasmasphere

Several basic models of frequency dynamics in quasi-periodic VLF emissions with spectral form repetition periods from 10 to 300 s are considered. In all cases, we are talking about manifestations of cyclotron instability of electron radiation belts that are well described within the framework of the plasma magnetospheric maser theory based on the averaged self-consistent system of quasi-linear equations for waves and particles. Not too clear spectral elements are characteristic of QP bursts, which are hisses with resonant modulation by geomagnetic pulsations of the 3-4 range mainly near the upper spectral boundary. Analysis of the equilibrium in the radiation belts reveals its possible instability caused by the difference in the pitch-angle dependences of the particle source power and the stationary distribution function. In the nonlinear regime of this instability, QP 2-radiations are formed, usually with a clear frequency increase in individual spectral fragments. The main objective of our work is the study of QP 2 emissions with a significant frequency dynamics. This opens up new possibilities for the diagnostics of space plasma and makes it possible to determine the conditions for occurrence of the frequently observed quasi-periodic emissions with large and very fast dynamics of the frequency spectrum, which can be represented as a product of functions dependent on time and frequency. The study of important details of the excitation of quasi-periodic VLF emissions with significant frequency dynamics inside the plasmasphere has interesting prospects for further research, and the already achieved level of understanding of magnetospheric processes has a real diagnostic potential.