Date of Award
Doctor of Philosophy (PhD)
Aerospace Engineering Sciences
Earth’s inner magnetosphere is a highly dynamic region consisting of various charged particle populations and current systems. Composed of relativistic electrons and protons, the radiation belt is a hazardous environment for both spacecraft and humans in space; while the variations of ring current, an electric current flowing around Earth consisting of energetic ions and electrons, can cause severe disruption of electrical systems on the ground. In the following, we focus on the dynamics of relativistic electrons (>~100 keV) in the inner radiation belt and slot region and energetic ions and electrons (>~keV) in the ring current, which are subject to influence from many different physical processes and commonly exhibit great changes on various spatial and temporal scales. Using data from SAMPEX and DEMETER satellites, we find that in the inner belt and slot region, though MeV electrons only exhibit flux enhancements during severe solar wind conditions, 100s of keV electron flux variations occur much more often. Using a radial diffusion model, a penetration event of 100s of keV electrons into the inner belt and slot region is modeled, and the results indicate that the penetration can be well explained by inward radial transport, but the radial diffusion coefficient is different from those of previous studies. Also, using data from the Van Allen Probes, we perform detailed analysis of 100s of keV electron pitch angle distributions (PADs) in the inner belt and slot region. A new type of PADs with minima at 90° persistent near the magnetic equator is unveiled, which is contradictory to the theoretical predictions from known physical processes and shows the complexity in the inner belt dynamics. Finally, the evolution of ring current ions and electrons are investigated during geomagnetic storms using data from the Van Allen Probes. The contribution of electrons and ions to the ring current energy is calculated and intriguing results are found. Our studies on the energetic electrons and ions in the inner belt, slot region and ring current contribute to a more comprehensive picture of inner magnetosphere dynamics.
Zhao, Hong, "Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current" (2015). Aerospace Engineering Sciences Graduate Theses & Dissertations. 117.