dorsal/arxiv
View SchemaEnhanced Phase Space Diffusion due to Chaos in Relativistic Electron- Whistler Mode Wave Particle Interactions in Planetary Magnetospheres
| Authors | W J Wykes, S. C. Chapman, G. Rowlands |
|---|---|
| Categories | |
| ArXiv ID | physics/9911075 |
| URL | https://arxiv.org/abs/physics/9911075 |
Abstract
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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"abstract": "The chaotic interaction between electrons and whistler mode waves has been\nshown to provide a mechanism for enhanced diffusion in phase space. Pitch angle\ndiffusion is relevant for the scattering of electrons into the loss cones, thus\nproviding a source for auroral precipitating electrons. A single whistler mode\nwave propagating parallel to the background magnetic field has resonance with\nthe electrons but the process is not stochastic. The presence of a second,\noppositely directed whistler wave has been shown previously to introduce\nstochasticity into the system, thus enhancing phase space diffusion. Here we\ngeneralise previous work to include relativistic effects. The full relativistic\nLorentz equations are solved numerically to permit application to a more\nextensive parameter space. We consider parameters scaled to intrinsic planetary\nmagnetospheres, for electron populations with \u0027pancake\u0027 velocity distributions\ni.e. large anisotropies in velocity space. We show that the diffusion is rapid,\noccuring on timescales of the order of tens of electron gyroperiods, and is\nstrongly sensitive to the wave amplitude, the wave frequency and the\nperpendicular velocity. Using Voyager 1 data we give an estimate of the\nwhistler wave amplitude in the Io torus at Jupiter and show that the two\nwhistler mechanism produces pitch angle diffusion of up to 10 degrees from an\ninitial pancake distribution, on millisecond timescales.",
"arxiv_id": "physics/9911075",
"authors": [
"W J Wykes",
"S. C. Chapman",
"G. Rowlands"
],
"categories": [
"physics.space-ph"
],
"title": "Enhanced Phase Space Diffusion due to Chaos in Relativistic Electron- Whistler Mode Wave Particle Interactions in Planetary Magnetospheres",
"url": "https://arxiv.org/abs/physics/9911075"
},
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