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Outward radial diffusion driven by losses at magnetopause

Shprits Y. Y., R. M. Thorne, R. Friedel, G. D. Reeves, J. Fennell, D. N. Baker, S. G. Kanekal, (2006), Outward radial diffusion driven by losses at magnetopause, J. of Geophys. Res. [Space Physics], 111, doi:10.1029/2006JA011657

Abstract

Loss mechanisms responsible for the sudden depletions of the outer electron radiation belt are examined based on observations and radial diffusion modeling, with L*-derived boundary conditions. SAMPEX data for October–December 2003 indicate that depletions often occur when the magnetopause is compressed and geomagnetic activity is high, consistent with outward radial diffusion for L* > 4 driven by loss to the magnetopause. Multichannel Highly Elliptical Orbit (HEO) satellite observations show that depletions at higher L occur at energies as low as a few hundred keV, which excludes the possibility of the electromagnetic ion cyclotron (EMIC) wave-driven pitch angle scattering and loss to the atmosphere at L* > 4. We further examine the viability of the outward radial diffusion loss by comparing CRRES observations with radial diffusion model simulations. Model-data comparison shows that nonadiabatic flux dropouts near geosynchronous orbit can be effectively propagated by the outward radial diffusion to L* = 4 and can account for the main phase depletions of outer radiation belt electron fluxes.

Authors (sorted by name)

Baker Fennell Friedel Kanekal Reeves Shprits Thorne

Journal / Conference

Journal Of Geophysical Research (Space Physics)

Acknowledgments

Work at UCLA was supported in part by IGPP LANL Collaborative Research minigrant, NASA grants NNX06AB84G and NNG04GN44G, and NSF GEM grant ATM‐0603191. Work at the Aerospace Corporation was supported by the LWS DATM grant NAG5‐10972. Work at Los Alamos was supported by NASA LWS program and the U.S. Department of Energy DREAM project.

Grants

ATM‐0603191 NAG5‐10972 NNG04GN44G NNX06AB84G

Bibtex

@article{doi:10.1029/2006JA011657,
author = {Shprits, Y. Y. and Thorne, R. M. and Friedel, R. and Reeves, G. D. and Fennell, J. and Baker, D. N. and Kanekal, S. G.},
year = {2006},
title = {Outward radial diffusion driven by losses at magnetopause},
journal = {Journal of Geophysical Research: Space Physics},
volume = {111},
number = {A11},
pages = {},
keywords = {magnetopause loss, radial diffusion, wave-particle interactions},
doi = {10.1029/2006JA011657},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2006JA011657},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006JA011657},
abstract = {Loss mechanisms responsible for the sudden depletions of the outer electron radiation belt are examined based on observations and radial diffusion modeling, with L*-derived boundary conditions. SAMPEX data for October–December 2003 indicate that depletions often occur when the magnetopause is compressed and geomagnetic activity is high, consistent with outward radial diffusion for L* > 4 driven by loss to the magnetopause. Multichannel Highly Elliptical Orbit (HEO) satellite observations show that depletions at higher L occur at energies as low as a few hundred keV, which excludes the possibility of the electromagnetic ion cyclotron (EMIC) wave-driven pitch angle scattering and loss to the atmosphere at L* > 4. We further examine the viability of the outward radial diffusion loss by comparing CRRES observations with radial diffusion model simulations. Model-data comparison shows that nonadiabatic flux dropouts near geosynchronous orbit can be effectively propagated by the outward radial diffusion to L* = 4 and can account for the main phase depletions of outer radiation belt electron fluxes.}
}