When Most of the Action is Hidden from View: A Synthesis of Observations of the Fast March 13, 2023 CME

Observational analyses of the evolution and dynamics of coronal mass ejection (CME) case study events tend to employ a holistic approach that takes advantage of multi-point and multi-regime measurements. Ideally, well-observed CMEs can be followed from their eruption off the solar disc via multi-wavelength remote-sensing data, through their coronal and heliospheric evolution via white-light imagery, and up to their arrival at a spacecraft of interest via in-situ measurements at one or more locations. In practice, events that can be tracked consistently through multiple regimes and from multiple viewpoints are understandably rare, and most CME detections are characterised by some “missing pieces in the puzzle” and/or limited observational perspectives. In this presentation, we shall focus on an event that was imaged remarkably well in white light (by both coronagraphs and heliospheric imagers) but had its source region and eruption dynamics completely hidden from view.

On March 13, 2023 an exceptionally fast and energetic CME was released from the solar far side as seen from Earth. Alas, the two other spacecraft equipped with disc cameras—STEREO-A and Solar Orbiter—were also imaging mostly the Earth-facing Sun, leaving a critical observational gap into the source, topology, and onset of the eruption. On the other hand, the coronal and heliospheric evolution of the CME were well observed from these three viewpoints as well as by Parker Solar Probe, which was located closer in longitude to the eruption’s source region. We present a synthesis of available (off-limb) EUV and white-light remote-sensing observations that aims to infer the complex eruption and early evolution of the event as well as to contextualise in-situ measurements at Parker Solar Probe, which was impacted by the CME at a heliocentric distance of ~0.25 au. Finally, we highlight the importance of observing the far side of the Sun, which, among other advantages, can fill a crucial observational gap required for multi-viewpoint measurements of every CME.