Magnetic reconnection in an anisotropic plasma: Observation and theory

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Title:	Magnetic reconnection in an anisotropic plasma: Observation and theory
Authors:	Hung,CC;Hau,LN;Hoshino,M
Contributors:	太空科學研究所
Keywords:	TEARING-MODE INSTABILITY;GYROTROPIC PLASMAS;RIEMANN PROBLEM;SLOW SHOCKS;MAGNETOTAIL;SHEET;DISCONTINUITIES;CLOSURE;WAVES
Date:	2011
Issue Date:	2012-03-27 17:32:17 (UTC+8)
Publisher:	國立中央大學
Abstract:	Space plasma usually exhibits temperature or pressure anisotropy with two distinct components, p(parallel to) and p(perpendicular to), denoting the pressure parallel and perpendicular to the magnetic field, respectively. This paper presents the first result of two-dimensional (partial derivative/partial derivative y = 0) magnetic reconnection with single X-line in anisotropic plasma based on gyrotropic magnetohydrodynamic (MHD) simulations. The field-line reconnection is initiated by imposing a localized resistivity on the Harris-type current sheet with a guide magnetic field B(y). It is shown that the observational feature of a slow shock (SS) followed by a contact discontinuity (CD) near the central sheet, across which the magnetic field is decreased and the pressure anisotropy is changed from p(parallel to) > p(perpendicular to) to p(parallel to) approximate to p(perpendicular to)?, as identified by Hoshino et al. (2000) in the Geotail data, may be reproduced in our simulations. For the initial equilibrium with relatively large pressure anisotropy of p(parallel to) >> p(perpendicular to), the steady reconnection layer may consist of SS followed by rotational discontinuity (RD) with both upstream and downstream states of SS being super-Alfvenic which is similar to the anomalous SS-RD compound structure found in the solar wind and magnetosphere. While for the cases of p(perpendicular to) > p(parallel to), the reconnection layer may consist of RD followed by SS and the reconnection rate is larger as compared to the cases of p(parallel to) >= p(perpendicular to). Citation: Hung, C.-C., L.-N. Hau, and M. Hoshino (2011), Magnetic reconnection in an anisotropic plasma: Observation and theory, Geophys. Res. Lett., 38, L18106, doi:10.1029/2011GL049117.
Relation:	GEOPHYSICAL RESEARCH LETTERS
Appears in Collections:	[Graduate Institute of Space Science] journal & Dissertation

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