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Stochastic charging of dust grains in planetary rings: Diffusion rates and their effects on Lorentz resonancesDust grains in planetary rings acquire stochastically fluctuating electric charges as they orbit through any corotating magnetospheric plasma. Here we investigate the nature of this stochastic charging and calculate its effect on the Lorentz resonance (LR). First we model grain charging as a Markov process, where the transition probabilities are identified as the ensemble-averaged charging fluxes due to plasma pickup and photoemission. We determine the distribution function P(t;N), giving the probability that a grain has N excess charges at time t. The autocorrelation function tau(sub q) for the strochastic charge process can be approximated by a Fokker-Planck treatment of the evolution equations for P(t; N). We calculate the mean square response to the stochastic fluctuations in the Lorentz force. We find that transport in phase space is very small compared to the resonant increase in amplitudes due to the mean charge, over the timescale that the oscillator is resonantly pumped up. Therefore the stochastic charge variations cannot break the resonant interaction; locally, the Lorentz resonance is a robust mechanism for the shaping of etheral dust ring systems. Slightly stronger bounds on plasma parameters are required when we consider the longer transit times between Lorentz resonances.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Schaffer, L.
(Cornell Univ. Ithaca, NY, United States)
Burns, J. A.
(Cornell Univ. Ithaca, NY, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: A1
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
Funding Number(s)
Distribution Limits

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