Effect of inflow density on ion diffusion region of magnetic reconnection: Particle-in-cell simulations

Journal Article · Tue Nov 15 00:00:00 EST 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3641964· OSTI ID:22047034

Wu, P; Shay, M A ^[1]; Phan, T D; Oieroset, M; Oka, M ^[2]

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1. Department of Physics and Astronomy, Bartol Research Institute, University of Delaware, 217 Sharp lab, Newark, Delaware 19716 (United States)
2. Space Science Laboratory, University of California, Berkeley, California 94720 (United States)

We perform a systematic study of the effect of inflow density on reconnection diffusion regions using a 2.5-D particle-in-cell code. The diffusion region structures are analyzed at times when all simulations have reconnected the same amount of magnetic flux. We find that reducing the inflow density from 1 to 1/100th of the current sheet density dramatically increases the diffusion region physical size and the reconnection rate. The width of the diffusion region scales with the upstream ion inertial length systematically. Consistent with the presence of counter-streaming inflowing ion beams near the x-line, the ion meandering width in the diffusion region also scales with the ion inertial length. The aspect ratio of the ion diffusion region remains a constant, independent of the inflow density. The quadrupole Hall magnetic field is reduced. The upstream magnetic field deviates from its asymptotic value by {approx}50% at the lowest simulated inflow density. The downstream ion outflow velocity scales linearly with the upstream Alfven speed with a multiplication factor {approx}0.4 < 1. When applied to magnetic reconnection in the Earth's magnetotail, this factor of 0.4 is a possible explanation as to why bulk flow velocities in the magnetotail are typically on the order of 500 km/s, while the Alfven speeds of inflowing plasmas can exceed 2000 km/s.

• OSTI ID: 22047034
• Journal Information: Physics of Plasmas, Vol. 18, Issue 11; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
ASPECT RATIO
ASYMPTOTIC SOLUTIONS
CHARGED-PARTICLE TRANSPORT
DIFFUSION
ELECTRIC CURRENTS
ION BEAMS
IONS
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
MAGNETOTAIL
MULTIPLICATION FACTORS
PLASMA
PLASMA DENSITY
PLASMA SIMULATION