A fast-moving halo CME was first observed in LASCO imagery around 16:00 UTC on December 17 following a powerful eruption on the farside of the Sun. No radio emissions were detected, and Earth-facing imagery confirms that this event was a result of a farside eruption, not directed toward Earth.
The CME was classified as an ER-type (Extremely Rare) by CCMC DONKI (Community Coordinated Modeling Center’s Database Of Notifications, Knowledge, Information), with an estimated speed of approximately 3 161 km/s (1 964 miles/s).
This speed is notably higher than some of the fastest historically recorded CMEs, such as those associated with the 2003 “Halloween storms,” which were recorded at speeds below 3 000 km/s.
If it had been Earth-directed, we’d be looking at G5 – Extreme geomagnetic storming on December 18 and 19.
Absolutely exceptionally fast CME (estimated speed ~3161 km/s). If this was an Earth-directed CME, we’d likely be looking at a G5 storm by late afternoon (UTC) tomorrow. Sun-Earth transit time would likely be <18 hrs. pic.twitter.com/o8UuEMHx9M
— Jure Atanackov (@JAtanackov) December 17, 2024
“This is truly an exceptionally rare kind of CME,” said Jure Atanackov, geologist and researcher associated with the Geological Survey of Slovenia (GeoZS) who reported extensively about this exceptional event. “Few recorded CMEs are as fast or faster than this one (~3 161 km/s). The 23 July 2012 far side event, known as the ‘Carrington event that missed us’ clocked in at ~3 300 km/s. The 2003 Halloween G5 storm CMEs were slower, <3 000 km/s.”
This is the fourth farside CME in the past 10 days, indicating the presence of a highly active sunspot currently hidden from view. This active region is likely located in the southern hemisphere near the central meridian. As the Sun rotates, Earth will face this active region next week.