A two‐dimensional hybrid simulation of the magnetotail reconnection layer

Abstract

Two‐dimensional (2‐D) hybrid simulations are carried out to study the structure of the reconnection layer in the distant magnetotail. In the simulation an initial current sheet separates the two lobes with antiparallel magnetic field components in the x direction. The current sheet normal is along the z direction. It is found that a leading bulge‐like magnetic configuration and a trailing, quasi‐steady reconnection layer are formed in a magnetic reconnection. If the duration of the reconnection is sufficiently long, the trailing reconnection layer will dominate the plasma outflow region. For the symmetric lobes with By = 0, two pairs of slow shocks are present in the quasi‐steady reconnection layer. The slow shocks are expected to be fully developed at a sufficient distance from the X line, where the separation between the two shocks is greater than a few tens of the lobe ion inertial length. The Rankine‐Hugoniot jump conditions of the slow shock are found to be better satisfied as the distance from the X line along the x axis increases. For the cases with By ≠ 0 in the two lobes, two rotational discontinuity‐like structures appear to develop in the reconnection layer. On the other hand, in the leading bulge region of a magnetic reconnection, no steady MHD discontinuities are found. Across the plasma sheet boundary layer the increase of the flow velocity appears to be much smaller than that predicted from the Rankine‐Hugoniot jump conditions for a steady discontinuity, and the increase in the ion number density is much larger. In addition, a large increase in the parallel ion temperature is found in the plasma sheet boundary layer. The 2‐D simulation results are also compared with the one‐dimensional hybrid simulations for the Riemann problem associated with the magnetotail reconnection. It is found that the 2‐D effects may lead to the presence of the non‐switch‐off slow shocks and thus the lack of coherent wave trains in slow shocks.

A Source of Energetic Particles Associated with Solar Flares

“…We use a two-dimensional hybrid code similar to that used by Lin & Swift (1995) and Lin & Xie (1997) in which electrons are treated as massless Ñuid and ions are treated as particles that satisfy the following equation of motion :…”

The onset of magnetic reconnection in the magnetotail

“…Beyond results pertaining to larger scales (e.g., Krauss-Varban and Omidi, 1995;Lin and Swift, 1996;Lottermoser et al, 1998), we now know that electron physical processes relying on the inertia of individual electrons, expressed as either pressure tensor, or bulk inertia effects, are required to facilitate the evolution of the large scale system. Previous analyses of time-dependent magnetic reconnection (Hewett et al, 1988;Pritchett, 1994;Tanaka, 1995a, b;Hesse et al, 1995;Kuznetsova et al, 1998;Hesse and Winske, 1998;Shay et al, 1998a, b;Sato, 1994, 1997;Cai and Lee, 1997;Hesse et al, 1999;Pritchett, 1994, Birn et al, 2000 have therefore begun to shed light on the electron behavior in different parameter regimes, primarily in the regions of low magnetic field.…”

Modeling Swarthmore spheromak reconnection experiment using hybrid code

“…As in the usual particle-in-cell (PIC) simulations, the ion particles are advanced at their exact positions, while the electric field, magnetic field and particle moments are calculated at discretized spatial grid points. We adopt the numerical scheme of the hybrid code by Swift [18], which has been used to global-scale simulations of various processes in the magnetosphere [9,12,17,34], including magnetic reconnection. In this paper, the scheme is applied to the geometry of SSX, with appropriate initial and boundary conditions.…”

“…In this paper, we report the development of a large-scale three-dimensional (3D) kinetic model for simulation of the SSX plasmas using a hybrid simulation code, which has been used for decades in space plasma research, including the numerical modeling of collisionless magnetic reconnection [9][10][11][12], Alfvén and various electromagnetic waves [13][14][15], collisionless shocks [16,17] and various boundary regimes where ion kinetic physics is dominant. In particular, the code includes fully kinetic ion physics, and thus can be used to investigate the reconnection physics ranging from the scales of ion Larmor radius to global Alfvén waves.…”