Simulation study of the Riemann problem associated with the magnetotail reconnection
- Auburn Univ., AL (United States)
- Univ. of Alaska, Fairbanks, AK (United States)
The structure of reconnection layer in the distant magnetotail is studied by solving the Riemann problem for the evolution of an initial current sheet using one-dimensional MHD and hybrid simulations. Initially, the current sheet with total pressure balance separates the plasmas and fields in the two lobes. In the presence of a nonzero normal magnetic field, which is due to the magnetic reconnection, the initial current sheet evolves to form the reconnection layer, which consists of various MHD discontinuities. First, the authors study the symmetric case with equal magnetic field strengths, equal plasma densities, and exactly antiparallel magnetic fields (B{sub y}=0) in the two lobes. The Petschek reconnection layer which contains two switch-off slow shocks, whose intermediate Mach number M{sub 1}=1, is obtained. In the hybrid simulation, the switch-off shock possesses a large-amplitude, left-hand-polarized rotational wave train of magnetic field in the downstream region. Each slow shock propagates to either lobe in the magnetotail. A strong temperature anisotropy with T{sub {parallel}}>T{sub {perpendicular}} appears in most region of the reconnection layer. This is due to the interpenetrating of ions between the two lobes and the backstreaming of ions from the downstream of each slow shock to the lobe. Second, the presence of a finite guide field in lobes (B{sub y}{ne}0) is considered in the simulation. It is found that the slow shocks become nonswitch-off shocks with an intermediate Mach number M{sub 1}<1, and two rotational discontinuities are also present in the hybrid simulation to bound the reconnection layer from, respectively, the two lobes. In addition, the hybrid simulations show that the presence of the finite B{sub y} destroys the coherent wave train in the reconnection layer if the lobe B{sub y0}{ge}0.08 B{sub x0}. 54 refs., 6 figs., 1 tab.
- OSTI ID:
- 227127
- Journal Information:
- Journal of Geophysical Research, Vol. 100, Issue A10; Other Information: PBD: 1 Oct 1995
- Country of Publication:
- United States
- Language:
- English
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