HR: 0830h
AN: SH21B-0160    [PDF]
TI: Structure of slow shocks and intermediate shocks in a magnetized plasma with heat conduction
AU: * Tsai, C
EM: cltsai@plasma.phys.ncku.edu.tw
AF: Department of Physics, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan, TW 70101 Taiwan
AU: Wu, B
EM: bhwu@plasma.phys.ncku.edu.tw
AF: National Space Program Office, 8F, 9 Prosperity 1st Road, Science-Based Industrial Park, Hsin-Chu, TW 30077 Taiwan
AU: Lee, L
EM: loulee@plasma.phys.ncku.edu.tw; loulee@nspo.org.tw
AF: National Space Program Office, 8F, 9 Prosperity 1st Road, Science-Based Industrial Park, Hsin-Chu, TW 30077 Taiwan
AB: The structure of slow shocks in the presence of a heat conduction parallel to the local magnetic field is simulated from the set of MHD equations. In our study, a pair of slow shocks is formed through the evolution of a current sheet initiated by the presence of a normal magnetic field. At first we consider the case that the tangential magnetic fields on the two side of initial current sheet are exactly antiparallel ($B_y=0$) to understand the effect of heat conduction, and the case that the tangential magnetic fields are not excctly antiparallel ($B_y\neq 0$). When $B_y=0$ it is found that the slow shock consists of two parts: the isothermal main shock and foreshock. Across the main shock, jumps in plasma density, velocity and magnetic field are significant, but the temperature is continuous. The plasma density downstream of the main shock decreases with time, while the downstream temperature increases with time, keeping the downstream pressure constant. The foreshock is featured by a smooth temperature variation and is formed due to the heat flow from downstream to upstream region. Finally the foreshock is found to reach a steady state with a constant width in the slow shock frame. When $B_y\neq0$ the process develops additional discontinuity, the time-dependent intermediate shock (TDIS), which is different from the rotational discontinuity. The plasma density and pressure increase and the magnetic field decrease across this TDIS. As in the $B_y=0$ case, the plasma density downstream of the main shock decreases with time, while the downstream temperature increases with time, keeping the downstream pressure constant. In some cases, the TDIS is embedded in the slow shock's foreshock structure initially, and then moves out of the foreshcok region. Define $\Psi$ as the initial anngle between the tangential magnetic fields on the two sides of current sheet. The propagation speed of foreshock leading edge decreases with smaller $\Psi$, and the steady state of foreshock width is reached earlier. Both pressure and temeprature downstream of the main shock increase with $\Psi$. The rotation angle of tangential magnetic field across TDIS develops with time, gradually reaching the final state. The results can be applied to the heating in the solar corona and solar wind.
DE: 2752 MHD waves and instabilities
DE: 7509 Corona
DE: 7524 Magnetic fields
DE: 7835 Magnetic reconnection
DE: 7851 Shock waves
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting