Comprehensive study on plasma waves in the magnetosphere

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The main topics which we focused on in this project are categorized as follows : 1. Generation and propagation of electromagnetic waves, 2. Relation of plasma wave activities to geomagnetic activities, and 3. Generation of electrostatic waves. In the topic 1, one of waves we investigated is the Auroral Myriametirc Radiation (AMR), which was discovered by Geotail spacecraft. We conducted the numerical calculation using the ray tracing method and compared obtained results on the propagation charcteristics with observational results. Our research shows that the AMR is radiated around the same region of AKR(Auroral Kilometoric Radiation) in the polar atmosphere. In the second topic, we performed the collaboration between Geotail and Equator-S satellites. We observed the dynamic motion and time variation of the plasma sheet structure using these two satellites and revealed the thinning effect and dipolalization of the geomagnetic field line first time from the multiple-spacecraft observatio … More ns. Further, we also examined the Geotail data which were observed in the low latitude boundary region and obtained that there exist different mechanisms which cause the plasma transportation from the magnetosheath into the magnetosphere. In the topic 3, we conducted the statistical analyses on the Electrostatic Solitary Waves (ESW), which are observed in the Plasma Sheet Boundary Layer (PSBL). The results are very consistent with the expected features of ESW by computer simulations. This agreement supports the model that the nonlinear evolution of electron beam instabilities lead to the formation of isolated electrostatic potential structures, which are proposed by computer simulations. We also examined the correlation between the NEN activities(Narrowband Electrostatic Noise)and electrons. We found the close relation between NEN activities and the existence of polar electrons. The structure of polar electron velocity distributions lead to destabilize the electron velocity space hole mode, which was proposed as the generation mechanism of NEN. Less