Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet

Abstract

Abstract. On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x = X C , where the north-south field component changes its sign. The plasmoid center corresponds to the socalled contact discontinuity that bounds the reconnected field lines in x < X C and the field lines without reconnection in x > X C . Hence, contray to the conventional prediction, the reconnected sheared field lines in x < X C are not spiral or helical, since they cannot be topologically connected to the field lines in x > X C . It is demonstrated that the resulting profiles of magnetic field components inside the plasmoid are, in principle, consistent with satellite observations. In the ambient magnetic field region outside the plasmoid too, the magnetic field profiles are in good agreement with the well-known observations of traveling compression regions (TCRs).

The structure and dynamics of a large-scale plasmoid generated by fast reconnection in the geomagnetic tail

“…On the contrary, the two-dimensional (2-D) plasmoid structure was studied on the basis of the spontaneous fast reconnection model (Ugai, 1995;Abe and Hoshino, 2001). Recently, we demonstrate that even without any initial northward magnetic field the magnetic field profiles inside the plasmoid, generated by the fast reconnection mechanism in the sheared current sheet, are, both qualitatively and quantitatively, in good agreement with the satellite observations; in particular, the north-south field component has the definite bipolar structure around the plasmoid center, where the east-west field component has the peak value (Ugai, 2010b). Also, the similar results are reported with a different numerical scheme by Shirataka et al (2006) on the basis of the spontaneous fast reconnection model, and similar structures are reported in Cluster observations .…”

“…The present simulation model is quite the same as Ugai (2010b), except that the results are shown with the coordinate system in Fig. 1.…”

“…As a sequence of Ugai (2010b), the present paper studies the structure and dynamics of large-scale plasmoid in detail. As illustrated in Fig.…”

“…Recently, the basic magnetic field profiles of large-scale plasmoid, generated by the fast reconnection mechanism, is studied (Ugai, 2010b), and it is demonstrated that they are, both qualitatively and quantitatively, in good agreement with the satellite observations (Ieda et al, 1998;Slavin et al, 2003) and, in particular, with those of the so-called night-side flux transfer events (Sergeev et al, 1992;Sormakov and Sergeev, 2008;Runov et al, 2009); outside the plasmoid too, the magnetic field profiles are consistent with the TCR signatures (Slavin et al, 1984(Slavin et al, , 1993Ugai and Zheng, 2006). As a sequence of Ugai (2010b), the present paper studies the structure and dynamics of large-scale plasmoid in detail.…”

“…As a sequence of Ugai (2010b), the present paper studies in detail the structure and dynamics of large-scale (principal) plasmoid, generated by the fast reconnection evolution in a sheared current sheet with no initial northward field component. The overall plasmoid domain is divided into the plasmoid reconnection region P and the plasmoid core region C. In the region P, the magnetized plasma with reconnected field lines are accumulated, whereas in the region C, the plasma, which was intially embedded in the current sheet and has been ejected away by the reconnection jet, is compressed and accumulated.…”