Significant rotation of spheromak CMEs from Sun to Earth: implications for numerical space weather predictions

Eleanna Asvestari - University of Helsinki; Jens Pomoell - University of Helsinki, Finland; Venla Koikkalainen - University of Helsinki, Finland; Emilia Kilpua - University of Helsinki, Finland

Session: Interplanetary CMEs and Solar Particle Events

Abstract

Coronal Mass Ejections (CMEs) are one of the primary drivers of space weather phenomena. Modelling of their arrival time, as well as their plasma and magnetic field properties are important for assessing the impact of a CME. Especially for Earth-directed events, the interplay between the magnetic field of the CME and the Earth determines largely the severity of the CME impact. Therefore, modelling CMEs as magnetised structures is of key importance for space weather forecasting. In these efforts, the spheromak model has recently received attention as a viable approach for simulating the magnetic structure of CMEs. In this work we focus in detail on how the spheromak flux rope magnetic field evolves as the CME propagates in different Interplanetary Magnetic Field (IMF) conditions. For this purpose we use EUHFORIA, a data-driven physics-based space weather model with varying background IMF settings. A preliminary result of our analysis is that after being injected in the modelling domain the spheromak experiences significant rotation about its axis of symmetry. This rotation can significantly alter the signature of the CME magnetic field as observed at 1 au, which in turn can significantly affect the predicted geoefficiency of the CME.