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| Titel |
Superdiffusion revisited in view of collisionless reconnection |
| VerfasserIn |
R. A. Treumann, W. Baumjohann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 32, no. 6 ; Nr. 32, no. 6 (2014-06-13), S.643-650 |
| Datensatznummer |
250121070
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| Publikation (Nr.) |
 copernicus.org/angeo-32-643-2014.pdf |
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| Zusammenfassung |
| The concept of diffusion in collisionless space plasmas like those near the
magnetopause and in the geomagnetic tail during reconnection is reexamined
making use of the division of particle orbits into waiting orbits and
break-outs into ballistic motion lying at the bottom, for instance, of Lévy
flights. The rms average displacement in this case increases with time,
describing superdiffusion, though faster than classical, is still a weak
process, being however strong enough to support fast reconnection. Referring
to two kinds of numerical particle-in-cell simulations we determine the
anomalous diffusion coefficient, the anomalous collision frequency on which
the diffusion process is based, and construct a relation between the
diffusion coefficients and the resistive scale. The anomalous collision
frequency from electron pseudo-viscosity in reconnection turns out to be of
the order of the lower-hybrid frequency with the latter providing a lower
limit, thus making similar assumptions physically meaningful. Tentative
though not completely justified use of the κ distribution yields
κ ≈ 6 in the reconnection diffusion region and, for the anomalous
diffusion coefficient, the order of several times Bohm diffusivity. |
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