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首页> 外文期刊>Physics of plasmas >Resonant micro-instabilities at quasi-parallel collisionless shocks: Cause or consequence of shock (re)formation
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Resonant micro-instabilities at quasi-parallel collisionless shocks: Cause or consequence of shock (re)formation

机译：准直接碰撞震动的共振微型稳定性：震动（重新）形成的原因或后果

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A case of two interpenetrating, cold and quasi-neutral ion-electron plasmas is investigated with the multi-fluid approach. We consider that one plasma floss quasi-parallel to the lines of a background magnetic field embedded in another static plasma. If the flow turns super-Alfvenic, we show that parallel R/L-modes and perpendicular X/O-modes become unstable and grow in amplitude. Within the linear theory, we find that the growth rate curve of an unstable mode has a maximum at some wavenumber specific to each mode. If we consider a shock like plasma configuration, we find that the fastest growing mode is the resonant one (with k similar to r(gi)(-1)) which strongly interacts with ions. In Particle-In-Cell (MC) simulations, we observe that a resonant wave with the same properties is excited during the early phases of shock formation. Once the wave becomes non-linear, it efficiently scatters ions and triggers the initial shock formation. This implies that the typical compression ratio of similar to 4 could naturally arise as a consequence of a highly resonant micro-physical process. We model the interaction of ions reflected from the reforming shock harrier in a weak-beam case, and we show that the upstream wave now matches the instability we expect from the equations. By using PIC simulations, we explain how the strong-beam resonant instability triggers shock formation in the non-linear stage, and how the weak-beam instability reforms and transmits the shock afterwards. The micro-instabilities that we study here could largely contribute to shock triggering as well as to the reformation and transmission of the shock itself. Published under license by AlP Publishing.
机译：用多流体方法研究了两个互穿，冷和准离子电子等离子体的情况。我们认为一个等离子体牙线与嵌入另一个静态等离子体中的背景磁场的线。如果流量转动超级宽度，我们表明并行R / L-MODES和垂直X / O-MODES变得不稳定并且幅度增长。在线性理论中，我们发现不稳定模式的生长速率曲线在每个模式的一些波数处具有最大值。如果我们考虑像等离子体配置等震荡，我们发现最快的生长模式是谐振的一种（类似于与离子强烈相互作用的r（gi）（ - 1）的k。在粒子细胞（MC）模拟中，我们观察到在冲击形成的早期阶段期间激发具有相同性质的共振波。一旦波变为非线性，它就会有效地散射离子并触发初始冲击形成。这意味着由于高度共振的微物理过程，类似于4的典型压缩比可以自然地出现。我们模拟离子反射的离子反射在弱梁壳中的改革冲击鹞反射，并且我们表明上游波现在与我们期望的不稳定性相匹配。通过使用PIC模拟，我们解释了强光束谐振不稳定触发了非线性阶段的冲击，以及弱束不稳定性的改革如何以及之后的震动。我们在此研究的微观载体可能主要有助于冲击触发以及震动本身的改革和传播。通过ALP发布在许可下发布。

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