Numerical study on propagation properties of interplanetary shocks

A two-dimensional, two-component MHD model and the PPM scheme are used in t his paper to investigate distribution of the density ratio (rho(2)/rho(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 up stream 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 axisymmetr ic background, the stronger magnetic field region is situated at the wester n 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 ratio s are essentially symmetrical with respect to the normal across the source center. (2) The velocity of the background solar wind exerts a great influe nce 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 d istribution of the relevant parameters. (3) The Presence of the current she et directly affects the distribution of the parameters along the shock wave front. When the initial position of the current sheet does not coincide wi th the disturbance source, the peaks of the ratios of density, gas pressure and magnetic field strength deviate westward in longitude, whereas the pea k 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 wi th the current sheet, there exists a peak on each part of the shock wave fr ont i.e. a double peak structure, and moreover, the kinetic pressure jump i s larger on the eastern part while the magnetic field strength is stronger on the western part.