Dynamics of the Low-Energy (E < 100 Ev) Ions in the Earth's Magnetosphere

This dissertation focuses on studying various properties of low-energy (E < 100 eV) ions in Earth's magnetosphere, including their pitch angle distributions (PADs), inter-hemispheric asymmetric features, and heating mechanisms. The first part of the dissertation investigates the pitch angle distributions of low-energy H+ ions in the Earth's outer magnetosphere. Statistical analysis was conducted using three years of observations from the Magnetospheric Multiscale (MMS) Hot Plasma Composition Analyzer (HPCA). The results reveal that the PADs of low-energy H+ ions exhibit asymmetric features due to interhemispheric asymmetry in the ionospheric outflow. The next part presents a case study of the asymmetric PADs by examining multi-satellite observations and global magnetohydrodynamics (MHD) simulation results. The observations demonstrate inter-hemispheric asymmetry in electron precipitation, favoring ionospheric outflow in the southern hemisphere. This finding is consistent with the simulation results obtained from the Space Weather Modeling Framework (SWMF)/BAT-S-RUS. Chapter 4 focuses on the heating of low-energy ions as they move along the plasmaspheric plume, utilizing six years of MMS HPCA observations and investigating wave-particle interactions. The analysis explores the impact of Electromagnetic Ion Cyclotron (EMIC) waves on the heating of low-energy ions. The results indicate that EMIC waves play a significant role in the heating process inside the plume under specific conditions. Furthermore, statistical analysis reveals the existence of hidden heating mechanisms, as most observations exhibit minimum resonant energies above 100 eV.