| Project/Area Number |
17403007
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | Tohoku University |
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Principal Investigator |
MISAWA Hiroaki Tohoku University, Graduate School of Science, Associate Professor (90219618)
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| Co-Investigator(Kenkyū-buntansha) |
OKANO Shoichi Graduate School of Science, 大学院・理学研究科, Professor (10004483)
SAKANOI Takeshi Graduate School of Science, 大学院・理学研究科, Research Associate (80271857)
TSUCHIYA Fuminori Graduate School of Science, 大学院・理学研究科, Research Associate (10302077)
YAMAZAKI Atsushi Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Research Associate (00374893)
SATOH Takehiko Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Professor (10297632)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥9,100,000 (Direct Cost: ¥8,800,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2005: ¥4,400,000 (Direct Cost: ¥4,400,000)
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| Keywords | satellite atmosphere / Io / plasma / acceleration process / remote sensing / optical observation / Jupiter / 国際情報交換 |
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| Research Abstract |
The main purposes of this study are the followings: 1) How the gases originated from Jupiter's satellite Io, which are considered to be main plasma source of Jupiter's magnetosphere, are generated and released from Io, 2) how the Iogenic plasma is accelerated to nearly corotation speed, and 3) how the Iogenic plasma is thermalized from the cold state just after the gas is generated to the hot state as known from ground based observations and planetary explorers. In order to investigate them, regular optical observations for the Iogenic gas and plasma had been carried out about one month a year at Mt. Haleakara, Maui, Hawaii which is one of the best optical observation sites in the world. And, numerical simulations had been made for the three scientific subjects, respectively.
1. Results of the observations: 1) These is always an east-west asymmetry of the Iogenic sodium gas which is distributed beyond several tens Jovian radii (sodium nebula). 2) The plasma speed near Io's orbit is alwa
… More
ys slower than the corotation speed, and the speed shows magnetic longitude dependence and dawn-dusk asymmetry. 3) Plasma temperatures near Io's orbit is derived for the parallel and perpendicular directions with respect to Jupiter's local magnetic field.
2. Results of the numerical simulations: 1) The dominant release process of the Iogenic gas (sodium nebula) would be dissociation or dissociative recombination of the Iogenic plasma, and the amount of the released gas would be largest/smallest when Io is in the dawn/dusk sides. 2) A current circuit would be made between the plasma near the Io orbit and Jupiter's ionosphere which has longitudinal asymmetry in the conductivity due to the local time dependence of the solar UV irradiation, and quasi-uniform longitudinal currents would make the observed accelerated plasma flow which is slower than the corotation speed with the dawn-dusk asymmetry. 3) Iion-cyclotron waves would be generated in the just ionized Iogenic plasma due to a plasma instability induced by the "ring distribution", and the waves might make the observed thermal conditions by thermalizing the plasma through the wave-particle interaction (pitch angel scattering). Less
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