Theory and simulations of discrete VLF emissions in the magnetosphere

We consider the results of theoretical and numerical studies of the of generation discrete VLF emissions in the Earth´s magnetosphere. The physics of cyclotron wave-particle interactions will be reviewed and current ideas on the mechanism forming the discrete spectrum of whistler-mode waves will be discussed. Two most important classes of the discrete emissions, i.e., triggered and chorus signals will be considered, and their common and specific features will be analyzed. We discuss the relationship between the model results and observations, and also possible application of similar mechanisms to the phenomena in the ion-cyclotron frequency range.