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arXiv physics/9911075physics.space-ph
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行星磁层中相对论电子-哨声模波粒相互作用中混沌引起的相空间扩散增强

Enhanced Phase Space Diffusion due to Chaos in Relativistic Electron- Whistler Mode Wave Particle Interactions in Planetary Magnetospheres

W J Wykes, S. C. Chapman, G. Rowlands

摘要:

电子和哨声模式波之间的混沌相互作用已被证明提供了一种机制,在相空间中增强扩散。俯仰角扩散与电子散射到损失锥中有关,从而为极光沉淀电子提供了一个来源。平行于背景磁场传播的单个哨声模波与电子发生共振,但这一过程不是随机的。第二个,方向相反的哨声波的存在下,先前已被证明引入系统的随机性,从而增强相空间扩散。在这里,我们概括以前的工作,包括相对论效应。完整的相对论洛伦兹方程数值求解,允许应用到更广泛的参数空间。我们认为参数缩放到内在的行星磁层,电子人口与“煎饼”的速度分布,即在速度空间中的大的各向异性。我们表明,扩散是迅速的,发生在几十个电子gyroperiods的顺序的时间尺度上,是强烈敏感的波的振幅,波的频率和垂直速度。使用旅行者1号的数据,我们给出了一个估计的哨声波振幅在木卫一环面在木星,并表明,两个哨声机制产生的俯仰角扩散高达10度,从最初的煎饼分布,毫秒的时间尺度。

英文摘要:

The chaotic interaction between electrons and whistler mode waves has been shown to provide a mechanism for enhanced diffusion in phase space. Pitch angle diffusion is relevant for the scattering of electrons into the loss cones, thus providing a source for auroral precipitating electrons. A single whistler mode wave propagating parallel to the background magnetic field has resonance with the electrons but the process is not stochastic. The presence of a second, oppositely directed whistler wave has been shown previously to introduce stochasticity into the system, thus enhancing phase space diffusion. Here we generalise previous work to include relativistic effects. The full relativistic Lorentz equations are solved numerically to permit application to a more extensive parameter space. We consider parameters scaled to intrinsic planetary magnetospheres, for electron populations with 'pancake' velocity distributions i.e. large anisotropies in velocity space. We show that the diffusion is rapid, occuring on timescales of the order of tens of electron gyroperiods, and is strongly sensitive to the wave amplitude, the wave frequency and the perpendicular velocity. Using Voyager 1 data we give an estimate of the whistler wave amplitude in the Io torus at Jupiter and show that the two whistler mechanism produces pitch angle diffusion of up to 10 degrees from an initial pancake distribution, on millisecond timescales.

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