MHD SIMULATION OF INTERACTIONS BETWEEN TWO NEIGHBORING INTERPLANETARY SHOCK WAVES——ENEGETIC EFFECTS

A MHD 2 1/2D,time-dependent model is used to investigate a series,individually of neighboring interplanetary shock wave interactions in the equatorial plane.For an azimuthal angular separation of 36 degree,between the centers of two disturbances,four different initial velocities,v_s=500,1000 2000 and 3000 km/s are considered in this paper.The results indicate: for the case of v_s=2000 and 3000 km/s,the two shock waves have already coalesced into a new shock within 1 AU,there are not any two peaks in the velocity,desity and temperature.From those parameters at 1 AU,it is difficult to identify whether this new shock wave coalesced from two shock waves,however,the magnetic field distribution in the new shock is very distinct from a single shock wave;for the case of v_s=1000 km/s,the two shock waves have not completely coalesced into a new shock wave,and the peak of shock parameters of each shock wave can be identified from their distributions;for the case of v_s=500 km/s,the coalescence would almost not occur,in fact,the two shock waves would decayed independently into ordinary MHD waves near 0.3 AU.