NUMERICAL STUDY ON PROPAGATION PROPERTIES OF INTERPLANETARY SHOCKS
YANG YU-LIN;LIU SHAO-LING ;HU YOU-QIU; LIU WEI (Department of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China)
A two-dimensional, two-component MHD model and the PPM scheme are used in this paper to investigate distribution of the density ratio (ρ_2/ρ_1), magnetic field strength ratio (B_2/B_1), gas pressure ratio (P_2/P_1), and kinetic pressure jump (Pk_2- Pk_1) along the shock wave front at 1AU in the heliospheric equatorial plane (the subscripts 1 and 2 represent the upstream and downstream sides respectively). Effects of the background solar wind, the width and initial propagation direction of the disturbance source, and the presence of the interplanetary current sheet on the distribution are also studied. The main conclusions are as follows. (1) In an axisymmetric background, the stronger magnetic field region is situated at the western part of the shock wave front whereas the kinetic pressure jump is larger at the eastern part. On the other hand, the density and gas pressure ratios are essentially symmetrical with respect to the normal across the source center. (2) The velocity of the background solar wind exerts a great influence on the kinetic pressure jump and the magnetic field strength ratio. The width of the disturbance source has no appreciable effect, but the initial propagation direction of the disturbance has a significant effect on the distribution of the relevant parameters. (3) The Presence of the current sheet directly affects the distribution of the parameters along the shock wave front. When the initial position of the current sheet does not coincide with the disturbance source, the peaks of the ratios of density, gas pressure and magnetic field strength deviate westward in longitude, whereas the Peak of the kinetic pressure jump and the normal across the source center are located at the same side of the current sheet. When the center coincides with the current sheet there exists a peak on each part of the shock wave front i.e. a double peak structure, and moreover, the kinetic pressure jump is larger on the eastern part while the magnetic field strength is stronger on the western pall.