Nonthermal High Energy Electron Acceleration from Shock Transition Region to Downstream Region

从激波过渡区到下游区的非热高能电子加速

• 批准号: 14340144
• 负责人: HOSHINO Masahiro
• 金额: $ 5.5万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340144/
• 关键词: shock wave; particle acceleration; surfing acceleration; numerical simulation; 惑星間空間衝撃波; ブーネマン不安定

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.

宇宙中的无碰撞冲击波的作用是重要的，因为它是从超音速等离子体体整体流能量转换为粒子/热能的关键机制。然而，对非热粒子加速机制的理解仍然很差。通过对冲击冲浪加速度的研究，分析了加速效率、能谱和冲击动力学。在本次资助研究期间，我们取得了以下成果：（1）双流不稳定性（布尼曼不稳定性）产生的大振幅静电波对电子冲击冲浪加速起着重要作用。我们发现，在非线性阶段，静电波可以与离子声波耦合，并且可以进一步增强波的振幅。讨论了当等离子体频率大于电子回旋频率时，大振幅波的发射。(2)In对于斜激波，由于洛伦兹力与高能电子逃逸之间的竞争作用，当激波角度为70 °时，冲浪加速效率最高。（3）双流不稳定性产生的相干静电波背后的湍流也有助于粒子加速的增强。(4)In超高马赫数激波，激波重组过程随马赫数增加而减弱。

项目成果

N.Shimada: "Electron-Ion Coupling Dynamics in the Shock Transition Region"Plasma Physics. 10. 1113-1119 (2003)

N.Shimada：“冲击转变区的电子-离子耦合动力学”等离子体物理学。

Electron heating and acceleration in the shock transition region: Background plasma parameter dependence

• DOI: 10.1063/1.1652060
• 发表时间: 2004-04
• 期刊: Physics of Plasmas
• 影响因子: 2.2
• 作者: N. Shimada;M. Hoshino

N.Shimada: "Electron Heating and Acceleration in the Shock Transition Region : Background Plasma Parameter Dependence"Plasma Physics. (in press). (2004)

N.Shimada：“冲击过渡区域中的电子加热和加速：背景等离子体参数依赖性”等离子体物理学。

Hoshino, M.: "Nonthermal Electrons at High Mach Number Shocks : Electron Shock Surfing Acceleration"Astrophys.J.. 572. 880-887 (2002)

Hoshino, M.：“高马赫数冲击下的非热电子：电子冲击冲浪加速”Astrophys.J.. 572. 880-887 (2002)

Forced magnetic reconnection

• DOI: 10.1017/s0022377817000782
• 发表时间: 2017-06
• 期刊: Journal of Plasma Physics
• 影响因子: 2.5
• 作者: G. Vekstein