Quasiperiodic ELF/VLF Emissions Detected Onboard the DEMETER Spacecraft: Theoretical Analysis and Comparison With Observations
Abstrakt
We present results of numerical simulation of quasiperiodic (QP) extra low frequency/very low frequency emissions performed by using a theoretical model of flow cyclotron maser based on a self-consistent set of equations of the quasi-linear plasma theory averaged over oscillations of waves and particles in a geomagnetic flux tube. Calculations were made for a wide range of plasma parameters (i.e., cold plasma density, L-shell, and energetic electron flux) in order to obtain a statistical relationship between various properties of QP emissions, such as the repetition period, the frequency bandwidth, the frequency drift rate, and the characteristic wave spectral energy density.
The theoretical results are compared with the results of a statistical study of QP emissions measured by the DEMETER spacecraft (Hayosh et al., 2014, https://doi.org/10.1002/2013JA019731). The simulation results are in a good agreement with the observation data in the case of reasonable choice of cold plasma density value and its dependence on the QP-source location (L-shell).
In particular, an increase in the frequency bandwidth of QP very low frequency waves with increasing central frequency of QP emissions, a decrease in the frequency drift rate of QP elements with increasing repetition period, and a decrease in the characteristic wave spectral energy density with increasing repetition period are confirmed.