Use of the Event Matrix for Chorus from the Lower Frequency Band to Determine Some Characteristics of Their Excitation Mechanism

The article studies quantitative characteristics of the mechanism of excitation of VLF chorus emissions by analyzing high-resolution data from the Van Allen Probes. A typical example of chorus with spectral forms in the lower frequency band (below half of the electron cyclotron frequency) in the region of the local minimum of the magnetic field behind the plasmapause in the middle magnetosphere is presented. A new method of analysis of quasi-harmonic signals recorded with high digitization frequency is proposed and implemented by the example of chorus in the lower frequency band. The results of wave field measurements in a high-resolution data channel are presented in the form of a rectangular event matrix, each row of which corresponds to one cycle of the wave process. In the event matrix, the rows corresponding to the fragments of the implementation that characterize the natural source of short electromagnetic pulses are selected. This made it possible to determine the complex eigenvalues of the characteristic equation of the source at the linear stage of chorus excitation. The values of the roots of the characteristic equation obtained by analyzing the data of chorus observations correspond to the implementation of chorus excitation by the amplification of noise electromagnetic pulses in a planar densification waveguide.