The relation between ion temperature anisotropy and formation of slow shocks in collisionless magnetic reconnection

[1] We perform a two-dimensional simulation by using an electromagnetic hybrid code to study the formation of slow-mode shocks in collisionless magnetic reconnection in low beta plasmas, and we focus on the relation between the formation of slow shocks and the ion temperature anisotropy enhanced at the shock downstream region. It is known that as magnetic reconnection develops, the parallel temperature along the magnetic field becomes large in association with the anisotropic plasma sheet boundary layer ion beams, and this temperature anisotropy has a tendency to suppress the formation of slow shocks. On the basis of our simulation result, we found that the slow shock formation is suppressed due to the large temperature anisotropy near the X-type region, but the ion temperature anisotropy relaxes with increasing the distance from the magnetic neutral point. As a result, two pairs of current structures, which are the strong evidence of dissipation of magnetic field in slow shocks, are formed at the distance ∣x∣ ≥ 115 λi from the neutral point.

[1]  B. Sonnerup,et al.  On the structure of resistive MHD intermediate shocks , 1989 .

[2]  J. Scudder,et al.  Observations of a slow‐mode shock at the lobe‐plasma sheet boundary in Earth's distant magnetotail , 1995 .

[3]  Y. Lin,et al.  A two-dimensional hybrid simulation of the magnetotail reconnection layer , 1996 .

[4]  N. Omidi,et al.  Magnetic structure of the reconnection layer and core field generation in plasmoids , 1999 .

[5]  M. Fujimoto,et al.  Acceleration of heavy ions in the magnetotail reconnection layer , 1994 .

[6]  Dan Winske,et al.  Kinetic Alfven Waves and Electron Physics in Oblique Slow Shocks , 2007 .

[7]  N. Omidi,et al.  Structure of slow magnetosonic shocks in low beta plasmas , 1989 .

[8]  M. Fujimoto,et al.  Ion dynamics and resultant velocity space distributions in the course of magnetotail reconnection , 1998 .

[9]  T. Mukai,et al.  Slow shock downstream structure in the magnetotail , 2000 .

[10]  T. Mukai,et al.  Two types of PSBL ion beam observed by Geotail: Their relation to low frequency electromagnetic waves and cold ion energization , 2005 .

[11]  Lev M. Zelenyi,et al.  Regular and chaotic charged particle motion in magnetotaillike field reversals: 1. Basic theory of trapped motion , 1989 .

[12]  T. Mukai,et al.  Ion dynamics in magnetic reconnection: Comparison between numerical simulation and Geotail observations , 1998 .

[13]  E. W. Hones,et al.  Slow‐mode shocks: A semipermanent feature of the distant geomagnetic tail , 1985 .

[14]  J. Kan,et al.  Shock Jump Conditions Modified by Pressure Anisotropy and Heat Flux for Earth's Bowshock , 1986 .

[15]  N. Omidi,et al.  Large‐scale hybrid simulations of the magnetotail during reconnection , 1995 .

[16]  M. Hoshino,et al.  Nonlinear evolution of plasmoid structure , 2001 .

[17]  M. Fujimoto,et al.  Right‐handed ion/ion resonant instability in the plasma sheet boundary layer: GEOTAIL observation in the distant tail , 1994 .

[18]  D. Winske,et al.  Electromagnetic ion/ion cyclotron instability at slow shocks , 1990 .

[19]  M. Scholer.  Undriven magnetic reconnection in an isolated current sheet , 1989 .

[20]  N. Omidi,et al.  Temperature anisotropy effects and the generation of anomalous slow shocks , 1995 .

[21]  M. Scholer,et al.  Ion kinetic effects in magnetic reconnection: Hybrid simulations , 1998 .

[22]  Swh Cowley,et al.  Energetic ion regimes in the deep geomagnetic tail: ISEE‐3 , 1984 .

[23]  Takaya Hayashi,et al.  Externally driven magnetic reconnection and a powerful magnetic energy converter , 1979 .

[24]  Harry E. Petschek,et al.  Magnetic Field Annihilation , 1963 .

[25]  Susumu Kokubun,et al.  Slow‐mode shocks in the magnetotail , 1995 .

[26]  Lou‐Chuang Lee,et al.  Simulation study of the Riemann problem associated with the magnetotail reconnection , 1995 .

[27]  D. Winske,et al.  Diffuse ions produced by electromagnetic ion beam instabilities. [in earth's bow shock , 1984 .

[28]  H. Karimabadi.  Steepening of Alfvén waves and its effect on the structure of slow shocks , 1995 .

[29]  Dan Winske,et al.  Hybrid simulations of collisionless reconnection in current sheets , 1994 .

[30]  T. Speiser.  Particle trajectories in model current sheets: 1. Analytical solutions , 1965 .

[31]  Dan Winske,et al.  Kinetic Alfvén waves and electron physics. I Generation from ion-ion streaming , 2007 .

[32]  Douglas S. Harned,et al.  Quasineutral hybrid simulation of macroscopic plasma phenomena , 1982 .