Space Plasma Transport by Kinetic Alfven Waves

这个项目将评估动态阿尔芬波传输太阳风（磁鞘）等离子体穿过地球磁场（磁层）外边界（磁层顶）的能力。传统上，磁鞘等离子体进入地球磁层的穿透半径不超过一个陀螺半径，这个边界应该是不可穿透的。然而，现场观测显示，穿透宽度超过10秒的陀螺半径，而且地球磁层的大部分等离子体确实由磁鞘等离子体填充。值得注意的是，磁层顶的边界层在磁鞘和磁层等离子体混合的地方总是充满低频电磁波动。有人认为这些波是动能阿尔芬波。理论研究表明，动态阿尔芬波可能有效地在磁场中传输等离子体。该项目将利用星系团航天器在磁层顶的多点场和等离子体观测来识别存在的波，并评估它们解释在那里看到的等离子体传输的能力。虽然这个项目是专门针对地球磁层顶的等离子体传输，但这个问题在许多物理情况下都是等离子体传输的核心，包括太阳上的磁环和托科马克和其他实验室等离子体设备中的等离子体传输。这项研究的结果将被纳入一系列旨在向K-12教师介绍地球空间环境物理学的讲习班。

This project will asses the ability of the kinetic Alfven waves to transport shocked solar wind (magnetosheath) plasmas across the outer boundary of the Earth's magnetic field (magnetosphere) known as the magnetopause. Classically this boundary should be impenetrable with magnetosheath plasma penetrating not more than a gyro-radius into the Earth's magnetosphere. However in-situ observations show penetration over widths of 10s of gyro-radii and indeed much of the plasma of the Earth's magnetosphere is populated by magnetosheath plasmas. Significantly, the boundary layer at the magnetopause where magnetosheath and magnetospheric plasma mix is invariably filled with low frequency electromagnetic fluctuations. It has been suggested that these waves are kinetic Alfven waves. Theoretical studies have suggested that kinetic Alfven waves may be effective in transporting plasmas across magnetic fields. This project will use multi-point fields and plasma observations from the Cluster spacecraft at the magnetopause to identify the waves that are present and evaluate their ability to account for plasma transport seen there. Although the project is specifically directed at plasma transport at Earth's magnetopause, the problem is central to plasma transport in many physical situations, including in magnetic loops on the sun and plasma transport in tokomaks and other laboratory plasma devices. The results from the research will be incorporated into a series of workshops designed to introduce K-12 teachers to the physics of Earth's space environment.