Understanding the global structure of the September 5, 2022, coronal mass ejection using sunRunner3D

Fast coronal mass ejections (CMEs) drive the most severe geomagnetic storms. In the past, forecasting their properties upstream of the Earth required developing and running complex numerical models. In this study, we present a new global MHD model for initiating and following the evolution of CMEs from the outer corona to 1 AU. Based on a successful astrophysical code, PLUTO, this new heliospheric model (sunRunner3D) is easy to install, set up, and run, requiring relatively modest computer resources. To illustrate this, we demonstrate how sunRunner3D can be used to interpret the signatures of the September 5, 2022, CME, which was observed – albeit to a limited extent – by various heliospheric spacecraft, including Parker Solar Probe, Solar Orbiter, BepiColombo, STEREO-A, and ACE. We explore the event’s dynamical evolution out to 1 AU, highlighting its relatively complex structure given its simple launch profile. We also investigate whether this event would have produced extreme space weather phenomena had the Earth been situated more directly in its path. Based on the model results and initial analysis of the magnetic structure of the erupting active region, we suggest that, indeed, the September 5, 2022 ICME would have had substantial geomagnetic consequences. Although sunRunner3D currently supports a modest range of options and features, with community adoption, we believe it could become a valuable tool for space weather applications.