1997 Fiscal Year Final Research Report Summary
Numerical study on plasma dynamics in the Earth magnetosphere in association with characteristic distributions of aurora and field-aligned currents
| Project/Area Number |
07804029
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | The University of Tokyo |
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Principal Investigator |
YAMAMOTO Takashi The University of Tokyo, Graduate Scool of Science, Research Associate, 大学院・理学系研究科 (40143375)
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| Project Period (FY) |
1995 – 1997
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| Keywords | Field-aligned Current / Auroral Omega Band / Auroral Oval / Interplanetary Magnetic Field / Charge Separation / Plasma Torus / Numerical Simulation / Interchange Instability |
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| Research Abstract |
So far, the theoretical models for the earth magnetosphere have normally assumed that the distribution of auroral particles with kinetic energies of 1-10 keV is uniform, in terms of the flux tube content, over the auroralzone. This implies that no charge separation occurs in that region, despite of the remarkable activity of aurora, and that boundary processes such as viscous interaction and magnetic reconnection play important roles in the auroral activity and production of region 1 field-aligned currents (FACs). We propose a new paradogm that during a period of southward interplanetary magnetic field (IMF), the so-called plasma 'torus' with plasma concentration on the auroral oval can be formed due to particle escape along the open field lines, and that distortion of the torus configuration by the two-cell convection results in the generaation of the region 1 and region 2 FACs. The plasma torus had been assumed to be absolutely interchange-unstable, and thus it had not been considered as a realistic distribution of the magnetospheric plasma. However, if reversal of the magnetic drift direction across the open-close boundary is taken into account, one can expect that the whole configuration of the torus can be maintained while the interchange instability occurs locally inside it. Our theory predicts that various phenomena such as production of region 0,1 and 2 FACs and formations of discrete aurora and omega band structure are interpreted as results of active behavior of the plasma torus which is "metabolized" through the processes of plasma flow into the tours from the solar wind the plasma escape. The purpose of our numerical simulation is to reproduce the metabolized torus as well as those auroral phenomena. Recently we have obtained the simulation results of the region 0,1 and 2 FACs and the formation of auroral omega band, which are consistent with the satellite servations.
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