Structure of fast shocks in the presence of heat conduction

Journal Article · Sat Dec 15 00:00:00 EST 2007 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2819673· OSTI ID:21072703

Tsai, C L; Chen, H H; Wu, B H; Lee, L C ^[1]

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1. Earth Dynamic System Research Center and Department of Physics, National Cheng Kung University, Tainan, 701 Taiwan and Institute of Space Science, National Central University, Jhongli, 320 Taiwan (China)

There are three types of magnetohydrodynamic (MHD) shocks: the fast shock, intermediate shock, and slow shock. The structure of slow shocks and intermediate shocks in the presence of heat conduction has been studied earlier [C. L. Tsai, R. H. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 9, 1185 (2002); C. L. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 12, 82501 (2005)]. Based on one-dimensional MHD numerical simulations with a heat conduction term, the evolution and structure of fast shocks are studied. The fast shock will form a foreshock in the presence of heat conduction. The foreshock is formed due to the heat flow from downstream to upstream and located in the immediate upstream of the main shock. In the steady state, the value of diffusion velocity V{sub d} in the foreshock is found to nearly equal the upstream convection velocity in the fast shock frame. It is found that the density jump across the main shock in high Mach number case can be much larger than 4 in the early simulation time. However the density jump will gradually evolve to a value smaller than 4 at steady state. By using the modified Rankine-Hugoniot relations with heat flux, the density jump across the fast shock is examined for various upstream parameters. The results show that the calculated density jump with heat flux is very close to the simulation value and the density jump can far exceed the maximum value of 4 without heat conduction. The structure of foreshock and main shock is also studied under different plasma parameters, such as the heat conductivity K{sub 0}, the ratio of upstream plasma pressure to magnetic pressure {beta}{sub 1}, Alfven Mach number M{sub A1}, and the angle {theta}{sub 1} between shock normal and magnetic field. It is found that as the upstream shock parameters K{sub 0}, {beta}{sub 1}, and M{sub A1} increase or {theta}{sub 1} decreases, the width of foreshock L{sub d} increases. The present results can be applied to fast shocks in the solar corona, solar wind, and magnetosphere, in which the heat conduction effects are important.

• OSTI ID: 21072703
• Journal Information: Physics of Plasmas, Vol. 14, Issue 12; Other Information: DOI: 10.1063/1.2819673; (c) 2007 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
ASTROPHYSICS
COMPUTERIZED SIMULATION
CONVECTION
DIFFUSION
FORESHOCKS
HEAT FLUX
MACH NUMBER
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA DENSITY
PLASMA PRESSURE
PLASMA SIMULATION
SHOCK WAVES
SOLAR CORONA
SOLAR WIND
STEADY-STATE CONDITIONS
THERMAL CONDUCTION