[PEM11-P01] Effects of Inclination/Rotation of Earth’s Magnetic Axis on Magnetosphere Simulated by Global MHD Model
キーワード：磁気圏電離圏結合、磁気圏MHDシミュレーション、電離圏効果
Recently, we have shown that the ionospheric Hall conductance distribution, owing to the polarization field generated by its nonuniformity, largely control the magnetospheric configuration and dynamics by using a global MHD model. The effects of the ionospheric conductance on the magnetosphere were also reported by previous studies based on other global models; for example, the current-voltage relationship in the solar wind-magnetosphere-ionosphere [Fedder and Lyon, 1987] and the plasma pressure distribution in the near-Earth region [Ridley et al., 2004]. These studies indicate that the ionospheric conductance is one of the most important settings in the global models to accurately simulate the magnetosphere.
On the other hand, in the development/improvement of the global MHD model in NICT, which was originally developed by Tanaka [1994] and Tanaka et al. [2010], introducing the inclination and rotation of Earth’s magnetic axis with respect to the rotation axis has been remained as one of the most difficult problems. In other words, in the present model, the precession between the magnetic axis and the rotation axis is not included. This means that the simulated magnetosphere will show a different structure and temporal development than the actual magnetosphere.
We, for the first time, equivalently introduce the precession by rotating the background conductance distribution due to solar illumination (i.e., depending on the geographic coordinate) with respect to the geomagnetic coordinate. (Improvement of the conductance setting in the auroral region is the next challenge.) In this paper, we will show how the simulated magnetosphere is changed by this improvement, focusing on the near-Earth plasma environment.
On the other hand, in the development/improvement of the global MHD model in NICT, which was originally developed by Tanaka [1994] and Tanaka et al. [2010], introducing the inclination and rotation of Earth’s magnetic axis with respect to the rotation axis has been remained as one of the most difficult problems. In other words, in the present model, the precession between the magnetic axis and the rotation axis is not included. This means that the simulated magnetosphere will show a different structure and temporal development than the actual magnetosphere.
We, for the first time, equivalently introduce the precession by rotating the background conductance distribution due to solar illumination (i.e., depending on the geographic coordinate) with respect to the geomagnetic coordinate. (Improvement of the conductance setting in the auroral region is the next challenge.) In this paper, we will show how the simulated magnetosphere is changed by this improvement, focusing on the near-Earth plasma environment.