Numerical Study of Characteristic of Interplanetary Shocks

Abstract

A two‐dimensional, two‐component MHD model and the PPM scheme are used to investigate distribution of the density ratio (), magnetic field strength ratio (), gas pressure ratio (), and kinetic pressure jump() on the shock wave front at 1 AU in the inner helioshperic equatorial plane (the subscripts 1 and 2 represent the upstream and downstream sides respectively). Effects of the background solar wind velocity, 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 axial symmetric 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 ratio 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 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 part.

Propagation Properties of Transient Shocks in the Inner Heliospheric Meridional Plane

“…Hu [11] discussed the propagation properties of flare-associated shocks in the heliospheric equatorial plane, and explained the statistical conclusion on the east-west deflection of the fastest propagation direction of shocks. Yang et al [12] and Jia et al [13] analyzed in detail the east-west asymmetry of the property distribution along the shock front near the Earth and pointed out that such an asymmetry stems from the east-west deflection of the fastest propagation direction of shocks and the spiral structure of the interplanstary magnetic field. Some researches also made simulation studies of the propagation properties of transient shocks in the meridional plane [14∼16] with emphasis on the influence of the HCS on the shock propagation.…”