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Evolution of electron fluxes in the outer radiation belt computed with the VERB code

Shprits Y. Y., D. Subbotin, B. Ni, (2009), Evolution of electron fluxes in the outer radiation belt computed with the VERB code, J. of Geophys. Res. [Space Physics], 114, doi:10.1029/2008JA013784

Abstract

Three-dimensional simulations of the dynamics of outer radiation belt electrons with the recently developed Versatile Electron Radiation Belt (VERB) code are presented. Simulations are preformed for an idealized storm with geomagnetic activity–dependent wave amplitudes that are parameterized as a function of the level of geomagnetic activity. Numerical experiments using the VERB code with various scattering processes (pitch angle diffusion, radial diffusion, and energy diffusion) indicate that diffusive processes are strongly coupled with each other and that they all should be included in realistic simulations of the radiation belts. We show that during storms, inward radial diffusion can produce significant accelerations to relativistic energies, while pitch angle scattering and energy diffusion produce a decrease and an increase in fluxes, respectively. We show that in the presence of high-latitude and low-latitude chorus, peaks in the radial profile of phase space density are formed between L of 4 and 6 during the recovery phase of a storm and are later smoothed by radial diffusion. Sensitivity experiments show that geomagnetic control of wave intensities plays a controlling role in the dynamics of radiation belt electrons. Numerical simulations indicate that electrons of 10–100 keV near geosynchronous orbit can reach MeV energies in the heart of the radiation belts by combined radial diffusion and in situ acceleration. We present two scenarios of acceleration of the plasma sheet electrons: (1) in the range of hundreds of keV by means of radial diffusion and (2) in the range of tens of keV by means of radial diffusion combined with local acceleration.

Authors (sorted by name)

Ni Shprits Subbotin

Journal / Conference

Journal Of Geophysical Research (Space Physics)

Acknowledgments

The authors would like to thank Richard Thorne for useful discussions and careful revision of this manuscript. This research was supported by USAF grant FA9550‐08‐1‐0140, Lab Research Fee grant 09‐LR‐04‐116720‐SHPY, and NSF grant ATM 0603191.

Grants

09‐LR‐04116720 ATM‐0603191 FA9550‐08‐1‐0140

Bibtex

@article{doi:10.1029/2008JA013784,
author = {Shprits, Yuri Y. and Subbotin, Dmitri and Ni, Binbin},
title = {Evolution of electron fluxes in the outer radiation belt computed with the VERB code},
journal = {Journal of Geophysical Research: Space Physics},
year = {2009},
volume = {114},
number = {A11},
pages = {},
keywords = {radiation belts, numerical modeling},
doi = {10.1029/2008JA013784},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2008JA013784},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008JA013784},
abstract = {Three-dimensional simulations of the dynamics of outer radiation belt electrons with the recently developed Versatile Electron Radiation Belt (VERB) code are presented. Simulations are preformed for an idealized storm with geomagnetic activity–dependent wave amplitudes that are parameterized as a function of the level of geomagnetic activity. Numerical experiments using the VERB code with various scattering processes (pitch angle diffusion, radial diffusion, and energy diffusion) indicate that diffusive processes are strongly coupled with each other and that they all should be included in realistic simulations of the radiation belts. We show that during storms, inward radial diffusion can produce significant accelerations to relativistic energies, while pitch angle scattering and energy diffusion produce a decrease and an increase in fluxes, respectively. We show that in the presence of high-latitude and low-latitude chorus, peaks in the radial profile of phase space density are formed between L of 4 and 6 during the recovery phase of a storm and are later smoothed by radial diffusion. Sensitivity experiments show that geomagnetic control of wave intensities plays a controlling role in the dynamics of radiation belt electrons. Numerical simulations indicate that electrons of 10–100 keV near geosynchronous orbit can reach MeV energies in the heart of the radiation belts by combined radial diffusion and in situ acceleration. We present two scenarios of acceleration of the plasma sheet electrons: (1) in the range of hundreds of keV by means of radial diffusion and (2) in the range of tens of keV by means of radial diffusion combined with local acceleration.}
}