Magnetohydrodynamic simulation of the interactionbetween two interplanetary magnetic cloudsand its consequent geoeffectiveness:2. Oblique collision

摘要

The numerical studies of the interplanetary coupling between multiple magneticclouds (MCs) are continued by a 2.5-dimensional ideal magnetohydrodynamic(MHD) model in the heliospheric meridional plane. The interplanetary direct collision(DC)/oblique collision (OC) between both MCs results from their same/different initialpropagation orientations. Here the OC is explored in contrast to the results of the DC. Boththe slow MC1 and fast MC2 are consequently injected from the different heliosphericlatitudes to form a compound stream during the interplanetary propagation. The MC1 andMC2 undergo contrary deflections during the process of oblique collision. Theirdeflection angles of 16011 and 16021 continuously increase until both MC-driven shockfronts are merged into a stronger compound one. The Oil, 16021, and total deflection angleAO (AO = 16011 + 16021) reach their corresponding maxima when the initial eruptionsof both MCs are at an appropriate angular difference. Moreover, with the increase ofMC2's initial speed, the OC becomes more intense, and the enhancement of 691 ismuch more sensitive to 602. The 18011 is generally far less than the 16021, and the unusualcase of 16011 _^2 16021 only occurs for an extremely violent OC. But because of the elasticityof the MC body to buffer the collision, this deflection would gradually approach anasymptotic degree. As a result, the opposite deflection between the two MCs, togetherwith the inherent magnetic elasticity of each MC, could efficiently relieve the external'compression for the OC in the interplanetary space. Such a deflection effect for the OCcase is essentially absent for the DC case. Therefore, besides the magnetic elasticity,magnetic helicity, and reciprocal compression, the deflection due to the OC should beconsidered for the evolution and ensuing geoeffectiveness of interplanetary interactionamong successive coronal mass ejections.