Modeling Electron Acceleration in the Earth's Magnetosphere
A key longstanding problem in space and astrophysical plasmas is determining the mechanism by which electrons can be accelerated to relativistic energies. Previous work by this group has focused on the Van Allen radiation belts, a region where the earth’s magnetic field traps large populations of energetic electrons. Relativistic electrons are often observed in the radiation belts, and it is in this region and at these energies that electrons are of particular interest, potentially damaging geosynchronous spacecraft and precipitating into the earth's atmosphere. Theoretical studies of wave-particle interactions often employ quasi-linear theory on the assumption that wave amplitudes are small. This group's observational studies indicate that this assumption may not be valid in the near-earth environment, and previous simulations on MSI resources have shown that the interaction of electrons with large amplitude waves may lead to nonlinear coherent effects that can result in scattering and energization of electrons to several MeV on subsecond time-scales. The researchers are continuing these studies of electron acceleration in the radiation belts, improving the accuracy and resolution of current models. They also plan to investigate electron and ion acceleration in the solar wind and in magnetotail reconnection.
Previous allocations were used to model radiation belt wave-particle interactions across a wide range of particle and wave parameters. This work is continuing, exploring the effects of more realistic wave packet structure on the wave-particle interaction. The group will also resume work on a 3D test particle code used to model wave-particle interactions in the magnetosphere, solar wind, and magnetotail. This will allow simulation of the acceleration of ions during magnetic "superstorms" for comparison to satellite observations of long-duration energy-banded ions. The group has worked closely with MSI staff on the development of these simulations, and will continue to do so as they refine their simulation models and move towards more detailed analysis and visualization of these simulations. The results of these simulations are critical to the NASA Radiation Belts Storm Probe mission on which the University of Minnesota is an Instrument PI, and to the Solar Probe mission for which the University will supply a high time resolution waveform instrument.
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