An empirical plasmasphere and trough density model: CRRES observations

Authors

  • B. W. Sheeley,

  • M. B. Moldwin,

  • H. K. Rassoul,

  • R. R. Anderson


Abstract

Combined Release and Radiation Effects Satellite (CRRES) sweep frequency receiver data were used to develop an empirical model of the plasmasphere and trough number density. The over 1000 CRRES orbits provided good statistical coverage of all local times between an L shell of 3 to 7. The CRRES density data were separated into plasmaspheric-like and trough-like by assuming a minimum density value for the plasmasphere as a function of L shell. For the plasmasphere the average number density (in cm−3) as a function of L shell (3 ≤ L ≤ 7) was found to be: np = 1390 (3/L)4.8 ± 440 (3/L)3.6. For the trough the average number density (in cm−3) as a function of L-shell (3 ≤ L ≤ 7) and magnetic local time (0 ≤ LT ≤ 24) was found to be nt = l24 (3/L)4.0 + 36(3/L)3.5 cos({LT-[7.7(3/L)2.0+12]}π/12) ± {78 (3/L)4.7 + 17 (3/L)3.7 cos[(LT - 22)π/12]}. No clear dependence on magnetic activity was found for either density model. This empirical model is an improvement over earlier models in that it is continuous in local time and can be used to track densities based on refilling history. The model standard deviations are representative of either early time or late time refilling of the trough or newly filled or saturated plasmaspheric densities.

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