Dr. Aaron Breneman, University of Minnesota
Title: "First Experimental Verification of Loss Cone Scattering of Energetic Electrons by Whistler Mode Hiss in the Plasmasphere"
Abstract: More than 40 years of theory have suggested that an electromagnetic plasma wave called plasmaspheric hiss is responsible for removing energetic electrons from the radiation belts in the region that overlaps with the plasmasphere. Until now, experimental verification of this process has eluded direct observation due to the inability of satellite particle detectors to resolve the loss cone at the magnetic equator.
Using multi-point observations from the Van Allen Probe satellites and BARREL (Balloon Array for Radiation Belt Relativistic Electron Losses) stratospheric balloon detectors we provide the first experimental verification of this process. Hiss signatures on the satellites show remarkable correlation with Bremsstrahlung x-ray counts on the distant balloons. Correlations are observed on timescales from tens of seconds to hours. Energies for first order cyclotron resonance between the hiss and electrons (10 to 200 keV), determined from in situ values of density, magnetic field and hiss wave normal angles from spacecraft A, are consistent with those of precipitated electrons.
Wave-particle interactions operate locally, on the scale of the electron gyroradius (few km). However, the measurements show that the interaction region is coherent over many thousands of km (up to 4 hours in MLT and 2.5 L shells), establishing that the process has global effects on the radiation belts.
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