Magnetospheric Access of Solar Particles and the Configuration of the Distant Geomagnetic Field

• Main Author: Evans, Lawrence Curtis
• Format: Thesis
• Language: English
• Published: 1972
• Subjects: South pole
• Online Access: https://thesis.library.caltech.edu/8691/; https://thesis.library.caltech.edu/8691/1/Evans_LC_1972.pdf; https://resolver.caltech.edu/CaltechTHESIS:10132014-144759243

The access of 1.2-40 MeV protons and 0.4-1.0 MeV electrons from interplanetary space to the polar cap regions has been investigated with an experiment on board a low altitude, polar orbiting satellite (OG0-4). A total of 333 quiet time observations of the electron polar cap boundary give a mapping of the boundary between open and closed geomagnetic field lines which is an order of magnitude more comprehensive than previously available. Persistent features (north/south asymmetries) in the polar cap proton flux, which are established as normal during solar proton events, are shown to be associated with different flux levels on open geomagnetic field lines than on closed field lines. The pole in which these persistent features are observed is strongly correlated to the sector structure of the interplanetary magnetic field and uncorrelated to the north/south component of this field. The features were observed in the north (south) pole during a negative (positive) sector 91% of the time, while the solar field had a southward component only 54% of the time. In addition, changes in the north/south component have no observable effect on the persistent features. Observations of events associated with co-rotating regions of enhanced proton flux in interplanetary space are used to establish the characteristics of the 1.2 - 40 MeV proton access windows: the access window for low polar latitudes is near the earth, that for one high polar latitude region is ~250 R ⊕ behind the earth, while that for the other high polar latitude region is ~1750 R ⊕ behind the earth. All of the access windows are of approximately the same extent (~120 R ⊕ ). The following phenomena contribute to persistent polar cap features: limited interplanetary regions of enhanced flux propagating past the earth, radial gradients in the interplanetary flux, and anisotropies in the interplanetary flux. These results are compared to the particle access predictions of the distant geomagnetic tail configurations proposed by Michel and Dessler, Dungey, and ...