Successive Interacting Coronal Mass Ejections: How to Create a Perfect Storm

Abstract Coronal mass ejections (CMEs) are the largest type of eruptions on Sun and main driver severe space weather at Earth. In this study, we implement a force-free spheromak CME description within 3D magnetohydrodynamic simulations to parametrically evaluate successive interacting CMEs representative heliosphere. We explore CME–CME interactions for range orientations, launch time variations, handedness quantify their geo-effectiveness via primary solar wind variables empirical measures disturbance storm index subsolar magnetopause standoff distance. show how interaction two moderate between Earth can translate into extreme conditions different radial distances maximize that induce geophysical impacts. particular, demonstrate orientation given have significant impact conservation loss magnetic flux, consequently B z , due reconnection with interplanetary field. This study thus implicates identification chirality in corona as an early diagnostic forecasting geomagnetic storms involving multiple CMEs.