Abstract
A review is presented of the status of our knowledge of electromagnetic cyclotron instabilities in multi‐component magnetosphericlike plasmas consisting of a hot anisotropic population and of additional cold plasma components, with special emphasis on the nonlinear phenomena. To achieve this, the results of a large number of computer simulation experiments are considered. While the paper deals primarily with naturally occurring magnetospheric phenomena, implications for the active space (seeding) experiments aimed at producing artificial auroras and consequently the verification of magnetospheric theories are also discussed.