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Numerical investigation of a compressible gyrofluid model for collisionless magnetic reconnection (Articolo in rivista)

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Numerical investigation of a compressible gyrofluid model for collisionless magnetic reconnection (Articolo in rivista) (literal)

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L. Comisso (1); D. Grasso (1); E. Tassi (2); F. L. Waelbroeck (3) (2012)
Numerical investigation of a compressible gyrofluid model for collisionless magnetic reconnection
in Physics of plasmas
(literal)

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1) Dipartimento di Energia, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy and Istituto dei Sistemi Complessi-CNR, Via dei Taurini 19, 00185 Roma, Italy 2) Centre de Physique Théorique, CNRS-Aix-Marseille Universités, Campus de Luminy, case 907, F-13288 Marseille cedex 09, France 3) Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712-1060, USA (literal)

Titolo

Numerical investigation of a compressible gyrofluid model for collisionless magnetic reconnection (literal)

Abstract

Ion Larmor radius effects on collisionless magnetic reconnection in the presence of a guide field are investigated by means of numerical simulations based on a gyrofluid model for compressible plasmas. Compressibility along the magnetic field is seen to favour the distribution of ion guiding center density along the neutral line, rather than along the separatrices, unlike the electron density. On the other hand, increasing ion temperature reduces the intensity of localized ion guiding center flows that develop in the direction parallel to the guide field. Numerical simulations suggest that the width of these bar-shaped velocity layers scale linearly with the ion Larmor radius. The increase of ion temperature radius causes also a reduction of the electron parallel velocity. As a consequence, it is found that the cusp-like current profiles distinctive of non-dissipative reconnection are strongly attenuated. The field structures are interpreted in terms of the behavior of the four topological invariants of the system. Two of these are seen to behave similarly to invariants of simpler models that do not account for parallel ion flow. The other two exhibit different structures, partly as a consequence of the small electron/ion mass ratio. The origin of these invariants at the gyrokinetic level is also discussed. The investigation of the field structures is complemented by an analysis of the energetics of the system. (literal)

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