Effect of two ion-species on the propagation of shear Alfven waves
Effect of two ion-species on the propagation of shear Alfven waves
复制标题
两种离子种类对剪切阿尔文波传播的影响
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
J. Maggs
中科院分区：
文献类型：
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作者：
G. Morales;S. Vincena;J. Maggs
本文报道了小横向小尺度剪切Alfven波在双离子等离子体中传播特性的理论模拟研究和实验研究结果。在双离子等离子体中，依赖于较重物质的质量，离子动力学效应可以变得突出，而显著的平行电场导致电子加速。该理论预测了在离子-离子混合频率和较低回旋频率的谐波之间出现频率传播间隙。在这些频带内，出现了混合了Alfven波的锥形传播特性和径向扩展的离子Bernstein模的空间结构。这些实验在加州大学洛杉矶分校的基础等离子体科学设施(BaPSF)进行，由环形天线发射的剪切波的空间映射组成。尽管探索了两种离子-物种组合，但只报道了氦-霓离子混合的结果。对于这种气体组合，发现了明显的剪切波传播间隙以及多个谐波之间的传播特征。在轴向磁场梯度存在的情况下，离子-离子混合频率处超过反射点的剪切波的消失也被记录下来。
The results of a theoretical modeling study and experimental investigation of the propagation properties of shear Alfven waves of small transverse scale in a plasma with two ion species are reported. In the two ion plasma, depending on the mass of the heavier species, ion kinetic effects can become prominent, and significant parallel electric fields result in electron acceleration. The theory predicts the appearance of frequency propagation gaps at the ion-ion hybrid frequency and between harmonics of the lower cyclotron frequency. Within these frequency bands spatial structures arise that mix the cone-propagation characteristics of Alfven waves with radially expanding ion Bernstein modes. The experiments, performed at the Basic Plasma Science Facility (BaPSF) at UCLA, consist of the spatial mapping of shear waves launched by a loop antenna. Although a variety of two ion-species combinations were explored, only results from a helium-neon mix are reported. A clear signature of a shear wave propagation gap, as well as propagation between multiple harmonics, is found for this gas combination. The evanescence of shear waves beyond the reflection point at the ion-ion hybrid frequency in the presence of an axial magnetic field gradient is also documented.