Ion acceleration in antiparallel collisionless magnetic reconnection: Kinetic and fluid aspects

Nicolas Aunai; Gérard Belmont; Roch Smets

doi:10.1016/j.crhy.2010.11.004

Ion acceleration in antiparallel collisionless magnetic reconnection: Kinetic and fluid aspects
[Accélération des ions dans la reconnexion magnétique antiparallèle, aspects cinétiques et fluides]

Nicolas Aunai ¹ ; Gérard Belmont ¹ ; Roch Smets ¹

¹ Laboratoire de physique des plasmas, École polytechnique, route de Saclay 91128 Palaiseau cedex, France

Comptes Rendus. Physique, Volume 12 (2011) no. 2, pp. 141-150.

Résumé
Abstract

A lʼaide dʼun code de simulation hybride bi-dimensionnel, nous étudions la zone de découplage ionique créée lors de la reconnexion magnétique non collisionnelle. Nous examinons les conséquences fluides des phénomènes cinétiques observés et discutons dans quelle mesure ils peuvent être expliqués dʼun point de vue fluide. La configuration initiale est une couche de courant antiparallèle dans un plasma de densité homogène. Nous discutons les différentes forces agissant sur le fluide ionique et montrons que les deux contributions dominantes sont la force électrique Hall et la force de pression agissant lʼune contre lʼautre. Lʼéquilibre dynamique, qui peut également se trouver dans des simulations fluides, est ici engendré par un effet cinétique. Nous étudions donc cette force de pression par une analyse des fonctions de distribution et montrons que celles-ci résultent dʼun mouvement de rebond électrostatique des ions sur les séparatrices. Ce mouvement de rebond est caractéristique de la zone de découplage ionique et le tenseur de pression des ions en résultant peut alors être considéré comme une nouvelle observable de la reconnexion magnétique non collisionnelle dans les données obtenues par satellite.

Using a two-dimensional hybrid simulation code, we study the ion acceleration in the vicinity of the ion decoupling region of collisionless magnetic reconnection. We investigate the fluid consequences of the observed kinetic phenomena and discuss to what extent it could be accounted for in fluid modeling. The initial setup is an antiparallel current sheet in a plasma with homogeneous density. We discuss the different forces acting on the ion bulk and show that the two dominant ones are the Hall electric force and the pressure force acting against each others. A dynamic equilibrium, which might also exist in fluid simulations, is here given by a kinetic effect. We therefore explain this pressure by an analysis of the ion distribution function and show that these are the result of an electrostatic bounce motion of the particles between the separatrices. This bounce motion is a characteristic of the ion decoupling region and therefore the resulting pattern of the pressure tensor may be considered as an additional observable feature of antiparallel reconnection in satellite data.

Publié le : 2011-03-01

DOI : 10.1016/j.crhy.2010.11.004

Keywords: Magnetic reconnection, Ion acceleration, Fluid and kinetic physics
Mot clés : Reconnexion magnétique, Accélération ionique, Physique fluide et cinétique

Affiliations des auteurs :

Nicolas Aunai ¹ ; Gérard Belmont ¹ ; Roch Smets ¹

¹ Laboratoire de physique des plasmas, École polytechnique, route de Saclay 91128 Palaiseau cedex, France

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     author = {Nicolas Aunai and G\'erard Belmont and Roch Smets},
     title = {Ion acceleration in antiparallel collisionless magnetic reconnection: {Kinetic} and fluid aspects},
     journal = {Comptes Rendus. Physique},
     pages = {141--150},
     publisher = {Elsevier},
     volume = {12},
     number = {2},
     year = {2011},
     doi = {10.1016/j.crhy.2010.11.004},
     language = {en},
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Nicolas Aunai; Gérard Belmont; Roch Smets. Ion acceleration in antiparallel collisionless magnetic reconnection: Kinetic and fluid aspects. Comptes Rendus. Physique, Volume 12 (2011) no. 2, pp. 141-150. doi : 10.1016/j.crhy.2010.11.004. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2010.11.004/

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