Wave-Particle Interaction in the Ionosphere and magnetosphere

Abstract

Wave-particle interactions that are important processes for the control of the electromagnetic states in the earth's magnetosphere are surveyed relatingto the auroral zone that is the most suitable window to clarify the various aspects of wave-particle interactions. The wave-particle interactions are classified using two-dimensional keys ; the first is the plasma parameter and the second is the frequency normalized by the electron cyclotron frequency. The plasma parameter is directly related to the place, such as ionosphere. plasmasphere, plasmapause and magnetosphere. The frequency normalized by the electron cyclotron frequency at a given region becomes a useful tool for analyses of the fundamental process of the wave generation both for the beam-wave instability or the other instability due to non Maxwellian type velocity distribution of the particles. Three channels are important for the generation of the plasma waves such as 1) between the plasma frequency and the upper hybrid resonance frequency, 2) between half electron cyclotron frequency and exact electron cyclotron frequency, and 3) near the lower hybrid resonance frequency. These channels largely contribute to the generation of the plasma waves and also wave-particle interactions relating to the electrostatic mode that produces strong interaction even with the low energy particles that occupy the majority of the population in the earth's magnetosphere. This evidence gives a revolutionary change to the old concept of wave particle interaction that has been concentrated only to the wave-particle interaction between the electromagnetic waves and the high energetic particles with energy larger than several tens keV.