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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Wobble motion of a particle's guiding center and the related magnetic moment
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Wobble motion of a particle's guiding center and the related magnetic moment

机译：粒子引导中心的摆动运动和相关的磁矩

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摘要

Because of the change in a magnetically trapped particle's instantaneous drift velocity, its guiding center does not bounce exactly along a field line but rather wobbles about it, when viewed in a frame of reference that moves with the bounce-averaged drift velocity. On the particle's drift shell the wobble orbit forms two linking narrow loops with a width of the order of the gyroradius. Each loop results in a magnetic moment distributed along the guiding field line. The line density of this "wobble magnetic moment" is comparable in magnitude with the line density of the usual (gyro) magnetic moment when the latter is distributed along the field line according to the time spent by the particle in each line element. The direction of the magnetic moment is perpendicular to the field line in the former, instead antiparallel to it in the latter; for one of the loops it points "outward" (i.e., in the direction of the outward field line normal), while for the other loop it points "inward." In addition, the direction of the wobble magnetic moment is independent of the particle's charge. In a plasma with a pressure gradient an electric current parallel to the magnetic field results :from the wobble magnetic moment, just as a perpendicular diamagnetic current arises from an inhomogeneous gyromagnetic moment distribution. This parallel current turns out to be of the same order of magnitude as the parallel current derived from the divergence of the drift current in the same plasma. General expressions are derived for the wobble of a particle's guiding center, the line density of the wobble magnetic moment, and the magnetization current in a plasma due to the wobble magnetic moment. For illustration, examples of particle motion in two-dimensional (line) dipole and three-dimensional (loop) dipole magnetic fields are shown. [References: 6]
机译：由于磁陷阱粒子的瞬时漂移速度发生了变化，当以随反弹平均漂移速度移动的参照系进行观察时，其引导中心不会精确地沿磁力线反弹，而是围绕其摆动。在粒子的漂移壳上，摆动轨道形成两个连接的，具有回旋半径数量级的窄环。每个回路都会产生沿引导线分布的磁矩。该“摆动磁矩”的线密度在大小上可与常规（陀螺）磁矩的线密度相比较，后者根据粒子在每个线元中所花费的时间沿磁场线分布​​。在前者中，磁矩的方向垂直于磁力线，而在后者中，磁矩的方向反平行。对于一个循环，它指向“向外”（即，在向外的场线法线的方向上），而对于另一个循环，它指向“向内”。另外，摆动磁矩的方向与粒子的电荷无关。在具有压力梯度的等离子体中，平行于磁场产生电流：由摆动的磁矩产生，就像垂直的反磁电流由不均匀的回旋磁矩分布产生一样。事实证明，该并联电流与在同一等离子体中由漂移电流的发散所产生的并联电流具有相同的数量级。对于粒子的引导中心的摆动，摆动磁矩的线密度以及由于摆动磁矩而在等离子体中的磁化电流，可以得出一般表达式。为了说明，示出了二维（线性）偶极子磁场和三维（环形）偶极子磁场中粒子运动的示例。 [参考：6]

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