According to the NOAA’s Space Weather Prediction Center (SWPC), the CME associated with the M8.1 flare is expected to reach Earth early to mid-day UTC on December 9, producing G3 – Strong geomagnetic storming and expanding the auroral oval toward mid-latitudes.
If the interplanetary magnetic field turns strongly southward upon impact, auroral activity could extend unusually far equatorward, allowing visibility across northern-tier U.S. states from Pennsylvania through Iowa to Oregon, and over comparable latitudes across northern Europe and southern Canada.
For observers in North America, the best chance to observe auroras will occur during the late evening hours of December 8 through the early morning of December 9 (local time), depending on the actual arrival time of the CME shock.
Bright and dynamic auroral activity is also expected across Alaska, northern Canada, Iceland, Scandinavia, and northern Scotland, where skies remain dark long enough for optimal visibility. Cloud cover and local light pollution will determine how far south auroras can be observed.
G3 – Strong geomagnetic storm potential effects include voltage irregularities in high-latitude power systems, surface charging, and increased drag on low-Earth-orbit satellites, temporary GPS degradation, and intermittent high-frequency radio communication.
The CME was generated by a strong M8.1 solar flare that erupted from Active Region 4299 at 20:39 UTC on December 6. The event began at 20:29 and ended at 20:49 UTC, producing a full-halo CME and a Type II radio emission with an estimated velocity of 1 143 km/s (710 miles/s). A 10 cm radio burst peaking at 1 100 sfu was also recorded between 20:35 and 20:39 UTC.
The region has a beta–delta magnetic configuration, indicating continued potential for additional M-class and possibly X-class flares in the coming days.
SWPC currently assigns a 65% probability of further M-class and 15% probability of X-class flares through December 8.