Propagation of interplanetary shock and its consequent geoeffectiveness

Using 2.5 dimensional ideal magnetohydrodynamic (MHD) equations, the propagation of the interplanetary shock and its consequent geoeffectiveness are Studied. The heliospheric current sheet (HCS)-heliospheric plasma sheet (HI'S) structure has some negative influences on the propagation of the interplanetary shock. When the shock propagates aslant the HCS, the segment on the opposite side of HCS with respect to shock nose is weaker than the other segment on the same side. The bending effect of the interplanetary shock on the magnetic field is ail important mechanism that can cause geomagnetic storm. The local normal (or shape) of the shock front exerts a crucial influence on the strength and direction of the bending effect. In the propagating direction of shock nose, it is a quasi-parallel shock mode and the strength of the bending effect is very weak. But on the edge of the shock nose, it is an oblique shock mode and the strength of the bending effect is strong. A concave is formed at the shock front across the HCS-HPS, at which the bending effect is efficiently intensified. The geoeffectiveness caused by the bending effect remarkably depends on the angular distance Delta theta(p) away from the HCS. The numerical results suggest that: whatever the direction of the interplanetary shock propagates in, there is no notable geoeffectiveness at the shock nose; when the shock propagates along the HCS, the most geoeffective regions are on the edge of HCS-HPS; when the shock propagates aslant. the HCS, the most geoeffective region is at the opposite side of HCS.