Origin and evolution of energetic particle populations in the magnetosphere

• Main Author: Klida, Michael M
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2011
• Subjects: Astrophysics; Electrical engineering; Studies
• ISBN: 1124755160; 9781124755168

There is a constant flow of electrons and ions into and out of the magnetosphere and the intricacies of the magnetosphere determine the paths that these particles take through it. Although the plasma in the magnetosphere generally originates in the ionosphere or the solar wind, the methods through which they and the means by which they propagate through the magnetosphere are more intricate. A method of determining the pitch angle distributions (PADs) from the energetic particle detectors on the Polar satellite is developed, including a process to extract distributions from partially damaged detectors. A survey of 384 equatorial passes of the Polar satellite on the nightside is used to create a statistical summary of pitch angle distributions (PADs) of energetic particles. In this region near local midnight, PADs with depressions at pitch angles of 90° are nearly ubiquitous outside of a radial distance of 5.5 RE. Additionally, a particle tracer is developed to trace the origin and evolution of particles in a simulated magnetosphere. Using various established models for the magnetic and electric fields, a Runge-Kutta method is used to numerically solve the fully-relativistic equation of motion from the Lorentz force. The particle tracer and observations from the Polar and THEMIS satellites are used to demonstrate that magnetopause shadowing is a viable loss mechanism for equatorially mirroring particles on the nightside. The simulations and observations will also show the constraints of inward convection of particles from the tail and demonstrated that the magnetopause can act simultaneously as a sink for high energy ions and electrons with pitch angles near 90° via magnetopause shadowing, and as a source for ions with pitch angles near 90° below ∼ 60 keV. Finally, observations from THEMIS are used to characterize the dawn and dusk flanks of the magnetopause near the equatorial plane. Full-sky plasma measurements with magnetic field information are used to depict both the magnetopause and the magnetosheath to show the viability of particles migrating inward from the magnetopause to the nightside region where they can make a significant contribution to the earth's ring current.