Observations and modeling of the trapping boundary of the radiation belts

Details Observations and modeling of the trapping boundary of the radiation belts Observations and modeling of the trapping boundary of the radiation belts

Sep 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt.........6a&link_type=abstract

Thesis (PhD). BOSTON UNIVERSITY, Source DAI-B 61/03, p. 1447, Sep 2000, 198 pages.

Physics

Scientific paper

The trapping boundary (TB) of the Earth's radiation belts is investigated. The radiation belts are regions extending several thousands of kilometers above the atmosphere and composed of energetic (>=10's of keV) charged particles, magnetically trapped and drifting azimuthally within the Earth's dipolar field. Within these belts particle fluxes tend to be highly anisotropic relative to the magnetic field. At the TB, the particle distributions become isotropic, a feature routinely observed at low altitudes in the high latitude region. In this thesis, the physics of the TB and its consequences are explored through a comprehensive analysis of its global configuration. This is achieved by developing physical models of the main features and analyzing some peculiar observations of the TB. This thesis focuses on two magnetospheric regions, low altitudes at high latitudes, where most observations are made, and high altitudes at low latitude, where the isotropic fluxes are likely produced. A model to calculate the latitude where the isotropic fluxes are observed is developed. Comparing this model with observations showed a good agreement with proton observations but not as well with electrons. The TB ion fluxes were investigated and a dayside source was suggested to explain the observations. A potential signature was found at the low altitude poleward edge of the TB of highly energetic fluxes simultaneously observed in the high altitude cusp. Furthermore, during active magnetic periods, fluxes of energetic neutral atoms were identified over the polar cap. The scattering process responsible for the isotropic fluxes seen at low altitudes is investigated. It was found that it did not produce isotropic distributions, but rather displaced particle velocities toward the field line and did not affect particles moving perpendicularly to the magnetic field line. This conclusion was supported by observations made by several satellites. Through this understanding, a new plasma population is proposed as an interpretation for some observations. Furthermore, the influence of these particle distributions on the ambient magnetic field was modeled and found to be appreciable. The results of the present work have created a new understanding of the earth's magnetosphere and radiation belts.

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