Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsm33a0344l&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SM33A-0344
Physics
2774 Radiation Belts
Scientific paper
Existing radial diffusion models of Earth's radiation belt electrons use energy-independent empirical timescales for losses. We present a 1d radial diffusion model using whistler-mode chorus wave and plasmaspheric hiss losses that depend on Kp, electron energy and L-shell. Bounce-averaged diffusion coefficients calculated from PADIE, and scaled by global Kp-driven models of wave intensity, are used to derive timescales for pitch-angle scattering into the loss cone. For a constant outer boundary, the model does not reproduce the losses at 1 MeV outside the plasmapause. At 270 keV, model fluxes outside the plasmapause decay when the observed flux decays, but the model underestimates the flux, and does not reproduce the rate of decay. With a time-dependent outer boundary based on fixed-energy CRRES MEA data, the model reproduces the flux magnitude and variability at L≥5 much better than the constant outer boundary model at 1 MeV, and better than existing empirical models; however at 270 keV, a time varying boundary brings no significant improvement in the flux variation near L=5. This suggests that losses are more important than transport at 270 keV. A time and energy dependent boundary results in low flux variations for L<4 at 1 MeV due to the more rapid recovery of flux dropouts at lower energies at the outer boundary; in addition, the flux is under-estimated during storms. When we include PADIE plasmaspheric hiss loss timescales optimized using CRRES data, the model reproduces the observed plasmaspheric flux magnitude and variability at 1 MeV; however at 270 keV the flux magnitude is too low within the plasmasphere. This may be due to the absence of substorm injections in the model. Our model improves on the flux magnitude and variability generated by similar models that use empirical loss rates and constant boundary conditions, and provides us with a powerful tool with which to examine the physical processes involved in radiation belt flux variability.
Glauert Sarah A.
Horne Richard B.
Lam Matthew
Meredith Nigel P.
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