Generation of Electrostatic Electric Fields and Radiation Belt Particle Acceleration to High Energy

Tuesday, 6 March 2018
Lakehouse (Hotel Quinta da Marinha)
Yan Song1, Robert L Lysak2 and John R Wygant2, (1)University of Minnesota Twin Cities, School of Physics and Astronomy, Minneapolis, MN, United States, (2)University of Minnesota, School of Physics and Astronomy, Minneapolis, MN, United States
Abstract:
Despite the tremendous progress made in the last several decades observationally and theoretically, we still lack a comprehensive theory that could account for dominant mechanisms of rapid acceleration of radiation belt relativistic particles, and explain the observational facts and provide predictions of the radiation belt processes under various external and internal conditions.

The effect of the solar wind and the role of ULF waves in the radiation belt particle acceleration have been broadly studied. The importance of local wave-particle interaction, for example, the interaction between whistler mode chorus waves with electrons in radiation belt particle acceleration has been well emphasized. However, the generation of electrostatic electric fields has not been noticed.

In general, electrostatic electric fields associated with charge separation is most powerful to directly accelerate particles to high energy. We will present the theory of the generation of electrostatic electric fields, and point out that the generation of electric fields is favored by a low plasma density and high magnetic shear. Nonlinear Alfvenic interactions between Alfven wave packets can produce EM plasma structures, such as Alfvenic Double Layers. These structures are dynamical in nature, where the Poynting flux carried by MHD waves continuously supplies energy to the Alfvenic Double Layers to maintain strong electrostatic electric fields for a fairly long time.

We point out that the nonlinear interaction of ULF wave packets in inhomogeneous radiation belts can generate localized electrostatic electric fields and may excite high frequency waves, such as observed whistler waves. The electrostatic electric fields play the important role in acceleration of radiation belt particles to high energy. In the process, ULF waves provide the energy for acceleration of relativistic particles in radiation belt and create the localized electrostatic electric fields. The electrostatic electric fields which are often accompanied by high frequency waves, play the main role in acceleration of radiation belt particles to high energy.

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