Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness: 2. Oblique collision

TL;DR

This study uses 2.5D MHD simulations to analyze how oblique collisions between magnetic clouds in interplanetary space affect their deflections and potential geoeffectiveness, highlighting the importance of collision angle and speed.

Contribution

It provides new insights into the deflection behavior of magnetic clouds during oblique collisions and their impact on space weather forecasting.

Findings

Oblique collisions cause significant deflections of magnetic clouds.

Deflection angles increase with initial speed and angular difference.

Collision elasticity leads to asymptotic deflection degrees.

Abstract

The numerical studies of the interplanetary coupling between multiple magnetic clouds (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 initial propagation orientations. Here the OC is explored in contrast to the results of the DC (Xiong et al., 2007). Both the slow MC1 and fast MC2 are consequently injected from the different heliospheric latitudes to form a compound stream during the interplanetary propagation. The MC1 and MC2 undergo contrary deflections during the process of oblique collision. Their deflection angles of $|\delta \theta_1|$ and $|\delta \theta_2|$ continuously increase until both MC-driven shock fronts are merged into a stronger compound one. The $|\delta \theta_1|$, $|\delta \theta_2|$, and total deflection angle $\Delta \theta$ ($\Delta \theta = |\delta \theta_1| + |\delta \theta_2|$) reach their corresponding maxima when the initial eruptions of both MCs are at an appropriate angular difference. Moreover, with the increase of MC2's initial speed, the OC becomes more intense, and the enhancement of $\delta \theta_1$ is much more sensitive to $\delta \theta_2$. The $|\delta\theta_1|$ is generally far less than the $|\delta\theta_2|$, and the unusual case of $|\delta\theta_1|\simeq|\delta\theta_2|$ only occurs for an extremely violent OC. But because of the elasticity of the MC body to buffer the collision, this deflection would gradually approach an asymptotic degree. Therefore, the deflection due to the OC should be considered for the evolution and ensuing geoeffectiveness of interplanetary interaction among successive coronal mass ejections (CMEs).