Global Modelling of Extreme Events and Their Space Weather Effects: The September 2022 ‘Labour Day’ CME

Coronal mass ejections (CMEs) are humongous eruptions of plasma and magnetic fields that permeate the heliosphere as they travel away from the Sun and major drivers of space weather activity at Earth and other solar system bodies. One of the most prominent challenges in heliophysics is the achievement of a complete understanding of the intrinsic structure and evolution of CMEs, and in particular of their spatiotemporal variability, which in turn would allow more precise forecasts of their arrival time and related space weather response. Of special interest are so-called extreme events, i.e. fast, large CMEs that tend to travel rapidly to 1 au and to drive the most severe geomagnetic effects. In this regard, one of the advantages of global magnetohydrodynamic (MHD) modelling is that results from a given simulation can be used not only to provide additional context to the available observations, but also to explore CME properties at any location in the heliosphere that may not feature corresponding spacecraft measurements.

On 5 September 2022, the Sun released a fast (~3000 km/s) CME from a far-sided active region (AR). The AR, the eruption, and the low-coronal evolution were observed by Solar Orbiter from its vantage point at 0.7 au and 150º west of Earth. Providentially, Parker Solar Probe was experiencing its 13th perihelion (2022-09-06T06:04 at 13.3 Rs and 85º west of Earth) just as it was being impacted by the CME. To investigate in detail the CME’s evolution from its eruption through its coronal and heliospheric propagation, we show an MHD simulation of the event using the Magnetohydrodynamic Algorithm outside a Sphere (MAS) code. Owing to the remarkable, diverse measurements that are available for this event, we can compare MAS modelling results with coronagraph observations from SOHO and STEREO-A, heliospheric imagery from Parker, as well as in-situ data from Parker and Orbiter. Additionally, we analyse synthetic time series of magnetic field and plasma properties at 1 au throughout the CME body, to evaluate the space weather effects that Earth would have experienced had it been somewhere along the CME’s path and to quantify the variability in geomagnetic response with respect to spacecraft crossing location. We conclude by discussing how combining 3D MHD modelling with novel data sets collected in the corona and inner heliosphere can help advance our current understanding of CME evolution and geoeffectiveness.