Magnetic reconnection in an anisotropic plasma: Observation and theory



[1] Space plasma usually exhibits temperature or pressure anisotropy with two distinct components, p and p, denoting the pressure parallel and perpendicular to the magnetic field, respectively. This paper presents the first result of two-dimensional (∂/∂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 By. 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 > p to pp, 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 pp, the steady reconnection layer may consist of SS followed by rotational discontinuity (RD) with both upstream and downstream states of SS being super-Alfvénic which is similar to the anomalous SS-RD compound structure found in the solar wind and magnetosphere. While for the cases of p > p, the reconnection layer may consist of RD followed by SS and the reconnection rate is larger as compared to the cases of pp.