Speaker
Description
First Name: Cecilia
Last Name: Mac Cormack
Affiliation: Catholic University of America, NASA Goddard Space Flight Center
All Authors: Cecilia Mac Cormack, Abril Sahade, Erika Palmerio, Evangelia Samara, Phillip Hess, Robin Colaninno and Teresa Nieves-Chinchilla
Abstract: On April 21, 2023, a complex filament eruption produced an Earth-directed coronal mass ejection (CME) that triggered the first severe geomagnetic storm of solar cycle 25. Although this CME appeared as a simple halo in LASCO observations, SoloHI observations revealed a more intricate structure. In this study, we explore the CME's complex morphology by integrating SoloHI observations with additional remote-sensing data and by simulating the eruption using the thermodynamic MHD model CORHEL-CME. Our primary objective is to understand the physical origin of the CME’s severe impact on Earth and to assess whether its complexity, as seen in remote-sensing observations, could have indicated its geoeffectiveness in advance. To this end, we model the source region as two interacting magnetic flux ropes and validate the early evolution of the eruption with extreme-ultraviolet and white-light observations from Solar Orbiter, SDO, SOHO and STEREO. We then compared the simulated CME arrival time and structure with in situ measurements, finding that the CME merged with a corotating interaction region (CIR) before reaching Earth. This interaction compressed the CME sheath, producing a sustained negative Bz component that later triggered the geomagnetic storm. The internal configuration of the magnetic flux rope, which also maintained a sustained southward component during its propagation toward Earth, intensified the storm into severe. This model–data comparison underscores the power of using MHD simulations, when validated by multi-viewpoint observations, to reveal hidden dynamical processes and improve the prediction of space weather impacts.