Modeling whistler wave generation regimes in magnetospheric cyclotron maser

Abstract

Abstract. Numerical analysis of the model for cyclotron instability in the Earth's magnetosphere is performed. This model, based on the self-consistent set of equations of quasilinear plasma theory, describes different regimes of wave generation and related energetic particle precipitation. As the source of free energy the injection of energetic electrons with transverse anisotropic distribution function to the interaction region is considered. A parametric study of the model is performed. The main attention is paid to the analysis of generation regimes for different characteristics of energetic electron source, such as the shape of pitch angle distributions and its intensity. Two mechanisms of removal of energetic electrons from a generation region are considered, one is due to the particle precipitation through the loss cone and another one is related to the magnetic drift of energetic particles.It was confirmed that two main regimes occur in this system in the presence of a constant particle source, in the case of precipitation losses. At small source intensity relaxation oscillations were found, whose parameters are in good agreement with simplified analytical theory developed earlier. At a larger source intensity, transition to a periodic generation occurs. In the case of drift losses the regime of self-sustained periodic generation regime is realized for source intensity higher than some threshold. The dependencies of repetition period and dynamic spectrum shape on the source parameters were studied in detail. In addition to simple periodic regimes, those with more complex spectral forms were found. In particular, alteration of spikes with different spectral shape can take place. It was also shown that quasi-stationary generation at the low-frequency band can coexist with periodic modulation at higher frequencies.On the basis of the results obtained, the model for explanation of quasi-periodic whistler wave emissions is verified.

Quasi-periodic ELF/VLF wave emissions in the Earth's magnetosphere: comparison of satellite observations and modeling

“…where G 1 and G 2 are known functions (see Pasmanik et al, 2004), ω BL is the electron gyrofrequency in the equatorial plane.…”

“…We use the model based on the self-consistent set of equations of the quasi-linear plasma theory for the distribution function F (µ, v, t) of energetic electrons and whistler wave spectral energy density ε(ω, t), averaged over oscillations of waves and particles between the mirror points and over the cross section of the interaction region (see Pasmanik et al (2004) for more detail):…”

“…This model describes different periodic regimes of wave generation with different shapes of the dynamic spectrum and can also be used for modeling the generation of QP emissions. Further study of this model was performed by Pasmanik et al (2004), where the dependence of possible generation regimes on the parameters of the energeticelectron source are analyzed. The results of Pasmanik et al (2004) demonstrate that the FCM model can produce a variety of periodic regimes of ELF/VLF generation with different types of dynamical spectra.…”

“…Further study of this model was performed by Pasmanik et al (2004), where the dependence of possible generation regimes on the parameters of the energeticelectron source are analyzed. The results of Pasmanik et al (2004) demonstrate that the FCM model can produce a variety of periodic regimes of ELF/VLF generation with different types of dynamical spectra. These results enable one to relate numeric and functional parameters of the model with features of the generation regimes.…”

“…Using the general results obtained by Pasmanik et al (2004), we choose suitable parameters of the simulation model, such as source characteristics and cold plasma density, for each experimental case. Good correspondence between the observations and simulations is demonstrated.…”