A Global Magnetohydrodynamic Simulation of the Birth and Cannibalism of Homologous Coronal Mass Ejections

Abstract

Homologous coronal mass ejections (CMEs) are sequential eruptions from the same active region. They are of particular space weather interest because they can interact and coalesce into compound ejecta, potentially amplifying their geomagnetic impact. Yet the full chain from recurrent initiation to magnetic merging has not been captured self-consistently in a single global simulation. We present a three-dimensional magnetohydrodynamic model that generates three homologous CMEs from a bipolar active region by recurrent photospheric shearing. All three eruptions follow the same initiation mechanism by tether-cutting reconnection within a recurrently formed sigmoid, while the later CMEs propagate significantly faster than the first. We demonstrate that this speed hierarchy arises from progressive coronal preconditioning; preceding eruptions evacuate the overlying corona, reducing both mass loading and ambient drag. The faster later CMEs catch up with their predecessors, and the compression between them forms inter-CME current sheets. Reconnection within these current sheets then progressively merges the interacting flux systems, completing the cannibalistic process. Synthetic coronagraph images reproduce the apparent coalescence of multiple white-light fronts. This simulation provides the first self-consistent global view of the birth, preconditioning, and cannibalistic interaction of homologous CMEs, bridging recurrent eruption initiation and inter-CME magnetic merging in the near-Sun corona.