Nonlinear Wave-particle Interactions

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The project is being funded jointly by the Division of Atmospheric Sciences of the Geosciences Directorate and by the Division of Physics in the Mathematical and Physical Sciences Directorate.This project will study nonlinear wave-particle interactions between relativistic electrons and whistler mode waves with a combination of theory/numerical simulation and experiment via the Large Plasma Device (LAPD) at UCLA. The motivation is to understand the dynamics of Earth's radiation belts, which is a critical unresolved problem in magnetospheric physics. There is a dichotomy between the two methods used to model wave-particle interactions: namely quasilinear diffusion theory and the test-particle simulations. The quasilinear theory breaks down in the outer radiation belt where large amplitude, narrow-band coherent waves have recently been observed. The porject will extend a recent test particle approach using a distribution of electrons and wave amplitudes and phases in order to derive a more self-consistent treatment of the interaction of energetic electrons with large amplitude coherent whistler waves. Experiments will be carried out on the LAPD involving the interaction of an energetic electron beam propagating from one end of the device with waves launched from the other end. The change in the pitch-angle and energy of the beam will be measured. The experimental results will compared to the theoretical/numerical simulations to improve and validate the theory.The project is headed by a young research scientist and will also involve a postdoctoral researcher and a graduate student. The project has societal impacts related to space weather.