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AGU: Geophysical Research Letters

 

Keywords

  • EMIC waves
  • radiation belts
  • nonlinear

Index Terms

  • Magnetospheric Physics: Radiation belts
  • Magnetospheric Physics: Energetic particles: precipitating
  • Magnetospheric Physics: Energetic particles: trapped

Abstract

Nonlinear interaction of radiation belt electrons with electromagnetic ion cyclotron waves

J. M. Albert

Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, Bedford, Massachusetts, USA

J. Bortnik

Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA

The rapid loss of radiation belt electrons in the main phase of geomagnetic storms is believed to be aided by EMIC waves, and is usually analyzed with quasi-linear theory. However, even moderate EMIC wave intensities easily cause resonant electrons to respond nonlinearly, with drastically different results. We map out the region of nonlinear behavior with a single parameter, and show that both the direction and magnitude of scattering can be estimated by analytical expressions. The nonlinear interactions typically lead to advection toward large pitch angles, rather than diffusion toward the loss cone. This is expected to reduce the overall loss rate and greatly affect the distribution of trapped electrons.

Received 27 April 2009; accepted 26 May 2009; published 26 June 2009.

Citation: Albert, J. M., and J. Bortnik (2009), Nonlinear interaction of radiation belt electrons with electromagnetic ion cyclotron waves, Geophys. Res. Lett., 36, L12110, doi:10.1029/2009GL038904.

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