This project will examine whether the recently-developed theory of BGK (Bernstein-Greene-Kruskal) wave modes in a magnetized plasma can account for the unusual features of electrostatic bursts (ESBs) observed in magnetospheric chorus waves in the outer magnetosphere and magnetospheric cusp of the Earth as well as the magnetospheres of Jupiter and Saturn. The ESB events can be quite large and understanding the source mechanism is likely to be relevant to processes that affect the radiation belts and the work thus has relevance to understanding and predicting space weather. The project will extend the BGK nonlinear theory and will compare the results with ESB events observed from a variety of satellite missions.