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Collisional relaxation: Landau versus Dougherty operator

Published online by Cambridge University Press:  13 October 2014

Oreste Pezzi*
Affiliation:
Dipartimento di Fisica and CNISM, Universitá della Calabria, 87036 Rende (CS), Italy
F. Valentini
Affiliation:
Dipartimento di Fisica and CNISM, Universitá della Calabria, 87036 Rende (CS), Italy
P. Veltri
Affiliation:
Dipartimento di Fisica and CNISM, Universitá della Calabria, 87036 Rende (CS), Italy
*
†Email address for correspondence: oreste.pezzi@fis.unical.it
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Abstract

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A detailed comparison between the Landau and the Dougherty collision operators has been performed by means of Eulerian simulations, in the case of relaxation toward equilibrium of a spatially homogeneous field-free plasma in three-dimensional velocity space. Even though the form of the two collisional operators is evidently different, we found that the collisional evolution of the relevant moments of the particle distribution function (temperature and entropy) are similar in the two cases, once an ‘ad hoc’ time rescaling procedure has been performed. The Dougherty operator is a nonlinear differential operator of the Fokker-Planck type and requires a significantly lighter computational effort with respect to the complete Landau integral; this makes self-consistent simulations of plasmas in presence of collisions affordable, even in the multi-dimensional phase space geometry.

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Type
Research Article
Copyright
Copyright © Cambridge University Press 2014