Understanding non-linear development of lower hybrid waves and ion acceleration driven by energetic ion injection through particle-in-cell simulation

概要

This thesis investigates the non-linear development of lower hybrid waves driven by
the ring-like energetic ions by means of one-dimensional, electromagnetic, particlein-cell (PIC) simulations with full ion and electron dynamics. We focus on the effects
of energetic ion injection on the ion-ring instabilities and the excitation mechanism
of the harmonic structure of lower hybrid waves, which are observed in the Earth’s
magnetosphere
Chapter 1 provides an overview of the basic plasma theory, the characteristic of
the lower hybrid wave, and the theory of the ion-ring instability. At the end of this
chapter, the purpose of this thesis is stated.
Chapter 2 describes the methodology of this thesis. The basic algorithm of the
PIC simulation and the simulation setting used in this thesis are described in this
chapter.
Chapter 3 examines the ion-ring instabilities driven by continuous energetic ion
injection. Most previous simulation studies solved initial value problems where
energetic ions were set up only at the initial time step, but our simulations adopt
the energetic ion injection model where energetic ions are gradually and continuously
injected into a plasma. The continuous injection allows us to investigate the longterm and more realistic development of the instabilities. We show that the energetic
ion injection significantly affects the non-linear development of the instabilities and
the energy transfer from energetic ions to bulk ions. The energetic ion injection
excites the broadband wavenumber range of the lower hybrid waves, which causes
bulk ion acceleration through the lower hybrid wave turbulence.
Chapter 4 examines the excitation mechanism of the harmonic structure of the
lower hybrid waves driven by the ring-like energetic ions. ...