ON THE INJECTION OF ELECTRONS IN OBLIQUE SHOCKS
ON THE INJECTION OF ELECTRONS IN OBLIQUE SHOCKS
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关于斜激波中电子的注入
DOI：
10.1093/mnras/278.4.1018
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发表时间：
1996
影响因子：
4.8
通讯作者：
A. Levinson
中科院分区：
文献类型：
--
作者：
A. Levinson
研究了超热电子在斜激波内部和后面产生湍流的机制，并考虑了电子注入的影响。它表明，而在准平行冲击的流动不稳定性占主导地位，在超光速冲击波驱动不稳定的压缩各向异性产生的结果，电子感应加速器加速穿越冲击波。在扩散近似下，注入过程受冲击结构和相应扩散系数的控制，并且由于场向和跨场输运性质之间的差异，准平行冲击与超光速冲击似乎显着不同。有效注射的要求进行检查，并发现是不那么严格的准平行冲击比超光速冲击。一个简单的估计表明，在马赫数超过，...，100，假设冲击的电子等离子体经历非常有效的无碰撞加热。还讨论了垂直冲击中电子注入的场线漂移引起的跨场扩散的影响。摘要研究了超热电子在斜激波内部和后面产生湍流的机制，并考虑了电子注入的影响。它表明，而在准平行冲击的流动不稳定性占主导地位，在超光速冲击波驱动不稳定的压缩各向异性产生的结果，电子感应加速器加速穿越冲击波。在扩散近似下，注入过程受激波结构和相应的扩散系数控制，由于场向和交叉场输运性质之间的差异，准平行激波与超光速激波的注入过程似乎明显不同。有效注射的要求进行检查，并发现是不那么严格的准平行冲击比超光速冲击。一个简单的估计表明，在马赫数超过，...，100，假设冲击的电子等离子体经历非常有效的无碰撞加热。本文还讨论了垂直激波中电子注入的场线漂移引起的交叉场扩散的影响。
The mechanism by which superthermal electrons generate turbulence inside and behind an oblique shock is studied, and the implications for electron injection are considered. It is shown that, whereas in quasi-parallel shocks the streaming instabil ity dominates, in superluminal shocks the waves are driven unstable by compressional anisotropies produced as a result of betatron acceleration of elec trons traversing the shock. The injection process, in the diffusion approximation, is controlled by the structure of the shock and the corresponding diffusion coefficient, and appears to be markedly different for quasi-parallel than for superluminal shocks, owing to the differences between the field-aligned and cross-field transport properties. The requirements for efficient injection are examined and found to be less stringent in quasi-parallel shocks than in superluminal shocks. A naive estimate suggests that efficient injection by this process may take place in superluminal shocks with Mach numbers in excess of ,..., 100, provided that the shocked electron plasma undergoes very effective collisionless heating. The implications of cross-field diffusion by field-line wandering for electron injection in perpendicular shocks are also discussed. ABSTRACT The mechanism by which superthermal electrons generate turbulence inside and behind an oblique shock is studied, and the implications for electron injection are considered. It is shown that, whereas in quasi-parallel shocks the streaming instabil ity dominates, in superluminal shocks the waves are driven unstable by compressional anisotropies produced as a result of betatron acceleration of elec trons traversing the shock. The injection process, in the diffusion approximation, is controlled by the structure of the shock and the corresponding diffusion coefficient, and appears to be markedly different for quasi-parallel than for superluminal shocks, owing to the differences between the field-aligned and cross-field transport properties. The requirements for efficient injection are examined and found to be less stringent in quasi-parallel shocks than in superluminal shocks. A naive estimate suggests that efficient injection by this process may take place in superluminal shocks with Mach numbers in excess of ,..., 100, provided that the shocked electron plasma undergoes very effective collisionless heating. The implications of cross-field diffusion by field-line wandering for electron injection in perpendicular shocks are also discussed.