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Transport inferred from consideration of particle orbits in drift turbulence

Bellan, P. M. (1993) Transport inferred from consideration of particle orbits in drift turbulence. Plasma Physics and Controlled Fusion, 35 (2). pp. 169-178. ISSN 0741-3335. http://resolver.caltech.edu/CaltechAUTHORS:BELppcf93

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Abstract

Particle orbits in the 2D potential hills/valley ('blobs') of low-frequency drift turbulence are analysed. For most of a given blob's lifetime a particle initially on the blob circulates on an orbit locked to that blob even though the blob shape and amplitude are changing. This locking corresponds to an adiabatic invariant being preserved. However, when the blob amplitude decreases to a critical value, the adiabatic invariant is destroyed, the locking ceases, and the particle detaches from the dying blob and attaches to a newly forming blob. This gives a detailed physical picture of the well known gyro-Bohm transport scaling D approximately gamma /k^2 where gamma is the turbulence autocorrelation time (corresponding to blob lifetime) and k is the perpendicular wavenumber (corresponding to blob diameter). It is further shown that gyro-Bohm transport is consistent with global measurements in a wide variety of experiments, in addition to the large tokamaks to which it has traditionally been applied. Finally, it is shown that ion orbit behavior becomes qualitatively different if the blobs become sufficiently sharp and steep.


Item Type:Article
Additional Information:© 1993 IOP Publishing Ltd. Received 9 March 1992, in final form 19 October 1992. The author acknowledges useful discussions with R A Stern about the instantaneous character of stochasticity and with G Hammett about gyro-Bohm diffusion. This work was supported by DOE Grant DE-FG03-86ER53232 and NSF Grant PHY-9114146.
Record Number:CaltechAUTHORS:BELppcf93
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:BELppcf93
Alternative URL:http://stacks.iop.org/0741-3335/35/169
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ID Code:404
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:09 Jun 2005
Last Modified:26 Dec 2012 08:40

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