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Research Abstracts Online
January 2009 - March 2010

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University of Minnesota Twin Cities
Institute of Technology
School of Physics and Astronomy
Department of Physics

PI: Cynthia A. Cattell

Using Particle Tracing Codes to Understand Acceleration of Relativistic Electrons via Electrostatic and Electromagnetic Waves

A key longstanding problem in space and astrophysical plasmas is determining the mechanism by which electrons can be accelerated to relativistic energies. Previous work at MSI focused on the Van Allen radiation belts, where the MeV electrons can damage spacecraft systems. These researchers’ studies have shown that the usual theoretical approach to studies of electron energization and scattering is inadequate to understanding radiation belt dynamics. The current theoretical studies of whistler acceleration take a quasi-linear approach and assume whistler amplitudes on the order of 1 mV/m. The researchers have recently discovered narrow-band whistler-mode waves in the Van Allen belt with electric field amplitudes an order of magnitude larger than previously observed. MSI particle tracing results have shown that these large waves (>240 mV/m) result in nonlinear coherent effects that can produce energization to several MeV on the short time-scales that are consistent with the change seen in MeV electron intensities during our event. The group has also shown large angle scattering consistent with observations by the low altitude SAMPEX satellite of so-called "relativistic electron microbursts,” which are particles lost from the radiation belts to affect the atmosphere. The researchers are continuing their improvements to the particle tracing code that models a single magnetic flux tube to examine effects of electrostatic waves, in addition to electromagnetic waves, to examine electron energization by the newly discovered waves, as well as in other regions where relativistic acceleration is occurring, including the solar wind and magnetotail reconnection. In addition, they will continue work on the full three-dimensional tracing code. They are also examining acceleration of ions during magnetic "superstorms” using the three-dimensional code to compare to satellite observations of long-duration energy banded ions. Results will be used to request NASA funds to support this work.

Group Members

Aaron Breneman, Research Associate
Nick Gryskiewicz, Undergraduate Student
Kris Kersten, Graduate Student
Ilan Roth, Space Sciences Laboratory, University of California, Berkeley, California
Justin Wilson, Undergraduate Student