Theory for Whistler Wave Amplification and Wave Particle Interactions in theMagnetosphere

摘要

Whistler waves are a type of very low frequency (VLF) radiation which propagatethrough the earth's magnetosphere. This phenomenon can occur as a result of a lightning discharge and can be produced using ground-based VLF transmitters. It is theorized that these signals travel through ducts centered on geomagnetic field lines. While passing through these ducts the waves are amplified through resonant interaction with electrons in the radiation belts which are following helical paths around magnetic field lines. A description of whistlers and the related topic of VLF emissions is presented in Chapter II, along with a description of how these effects change the properties of the ionosphere. Starting with the Lorentz force equation, the equations of motion for electrons in the magnetosphere are developed in Chapter III. These equations are numerically integrated along with a wave equation developed in Chapter IV. The results of the simulation are presented in Chapter V for the idealized case of a monoenergetic beam of electrons. High and low gains in the wave amplitude are observed for both strong and weak initial VLF fields. The simulation is also run using distributions to represent the initial energies of the electrons in the radiation belts. Chapter VI presents some possible ways to make the simulation more realistic along with a summary of the similarities between the theory presented and Free Electron Laser theory.