Complex active region 13514, located in the northwestern edge of the solar disc, produced a powerful X2.8 solar flare on the 14th December, peaking at 17:02 UT. This flare is the strongest in this solar cycle, and the largest seen in the last six years. The associated coronal mass ejection (CME) is an asymmetric full-halo, with the bulk of the ejecta heading away from Earth. Modelling suggests that a glancing blow from the CME could arrive late on the 16th, or early on the 17th December.
The strength of any geomagnetic storm depends on the nature of the CME impact; what proportion of the CME is Earth-directed, and the strength and direction of the interplanetary magnetic field contained in the CME. A geomagnetic storm is predicted, and activity could range from STORM G1 to potentially STORM G3, if the impact is significant.
Active region 13514 has also produced several C- and M-class solar flares over the past week, some with associated coronal mass ejections. A CME arrival from one of these smaller events arrived at Earth 11:46 UT on 15th December and we could see ACTIVE to STORM G1 effects in the hours following. Other CMEs associated with M-class flare events may combine with the CME associated with the X2.8 event.
Assuming clear, cloud-free, dark skies, there is an increased chance of seeing the aurora on 16th and 17th December. Those in Scotland, northern England and Northern Ireland have the best chance if the weather and timing of the CME arrivals is favourable.
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