15:45 〜 16:00
[PEM06-12] EISCAT_3D及び関連観測に基づくイオン上昇流/イオン流出の研究
キーワード：EISCAT, ionosphere, M-I coupling
An important phenomenon of magnetosphere-ionosphere coupling is the formation of upwelling ions in the topside polar ionosphere. These upflows can be a significant loss of atmospheric gasses into interplanetary space and a significant source of magnetospheric plasma, which may also affect the dynamics of the magnetosphere. Key processes for upward ion flows in the topside ionosphere are suggested to be frictional heating, ambipolar diffusion driven by a heated electron gas, and transverse ion acceleration produced by plasma waves. It is critical to determine the relative importance of the different mechanisms in operation and to understand the 3D distribution and composition of the upflowing ions and neutrals. Moreover, there are several transitions of upflowing ions, for examples, from chemical to diffusion dominance at 500-800 km altitude, from subsonic to supersonic flow at 1000-2000 km altitude, and from collisional to collisionless region at 1500-2500 km altitude. EISCAT_3D is one of the most suitable measurements to investigate such transitions because of its wider height coverage (up to about 2000 km) along the field line. EISCAT_3D will have more transmitter power density and higher sensitivity than those of the current Tromso UHF radar, and will give information of accurate thermal ion velocity, upward flux, and ion composition (O+, H+, and hopefully NO+). A combination of the EISCAT_3D, ground-based optical instruments, and in-situ measurements is definitely essential to solve several key questions of ion upflow and outflow study. In this paper, we show potential investigations of ion upflow and outflow using the EISCAT_3D, and also discuss a desirable combination of the EISCAT_3D and its related observations for the ion upflow and outflow study.