| Project/Area Number |
14340144
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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 | 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 |
HOSHINO Masahiro The University of Tokyo, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (90241257)
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| Project Period (FY) |
2002 – 2004
|
| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥8,600,000 (Direct Cost: ¥8,600,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2003: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2002: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Keywords | shock wave / particle acceleration / surfing acceleration / numerical simulation / 惑星間空間衝撃波 / ブーネマン不安定 |
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| Research Abstract |
The role of collisionless shock waves in the Universe is important as the key mechanism of energy conversion from super-sonic plasma bulk flow energy into particle/thermal energy. However, the understanding of the non-thermal particle acceleration mechanism remains poor. By focusing on the shock surfing acceleration, we investigated the acceleration efficiency, energy spectrum, and shock dynamics. During this Grant-in-Aid research period, we obtained the following results :
(1)The large amplitude electrostatic waves generated by two-stream instability (Buneman instability) plays an important role on the electron shock surfing acceleration. We found that the electrostatic wave can couple with the ion acoustic waves in the nonlinear stage, and the wave amplitude can be further enhanced. Also we discussed that the emission of the large amplitude waves occurs when the plasma frequency is larger than the electron cyclotron one.
(2)In oblique shock waves, due to the competing effect between the Lorentz force and the escape of high energy electrons, the maximum efficiency of the surfing acceleration occurs when the shock angle becomes about 70 degree.
(3)The turbulence behind the coherent electrostatic waves generated by two-stream instability also contributes to the enhancement of particle acceleration.
(4)In super-high Mach number shock waves, the shock reformation process becomes weak as increasing Mach number.
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