Moderate M1.3 solar flare erupts at 18:27 UTC on December 21, 2025

A moderate M1.3 solar flare erupted at 18:27 UTC on December 21, 2025.

Today’s flares include several C-class events: a C1.8 flare from region 4317 at 02:14 UTC, a C1.3 flare from region 4316 at 11:54 UTC, another C1.3 from region 4317 at 12:11 UTC, and a C1.3 from region 4315 at 12:47 UTC. Other activity today included radio emissions and optical flares from regions 4315 and 4316. No M-class or X-class flares besides the reported M1.3 event were listed among today’s edited events.

In 24 hours to 12:30 UTC on December 21, solar activity was at low levels. The majority of observed activity was C-class flares produced by region 4317, which showed growth after rotating into full view. Some additional growth was seen in regions 4311 and 4316. No Earth-directed coronal mass ejections were detected in available imagery.

Solar activity is expected to remain at low levels, though there is a slight chance for additional M-class flares through December 23.

Active sunspot regions presently observed on the Earth-facing solar disk include AR 4311 (N04W41 – Beta), AR 4312 (N19E32 – Alpha), AR 4314 (N24E31 – Beta), AR 4315 (N20E49 – Beta), AR 4316 (S00E40 – Beta), and AR 4317 (N13E73 – Beta).

Over the past 24 hours, the greater than 2 MeV electron flux reached high levels with a peak of 7 320 pfu. The greater than 10 MeV proton flux remained at background values. The greater than 2 MeV electron flux is expected to return to normal to moderate levels from December 21 to 23, while the greater than 10 MeV proton flux is forecast to persist at background throughout the period.

Over the past 24 hours, the solar wind environment became enhanced with the onset of corotating interaction region effects. The total magnetic field peaked at 15 nT, with the Bz component dipping southward to -12 nT. Solar wind speeds increased from around 450 km/s to nearly 650 km/s. Enhanced solar wind conditions are expected to persist through December 23 due to continuing CIR and coronal hole high-speed stream influences.

The geomagnetic field reached active levels in response to corotating interaction region effects. Active geomagnetic conditions are likely to continue, with a chance for G1 – Minor storm periods on December 21. Periods of G1 – Minor storming are likely, and there is a possibility for G2 – Moderate storm periods, on December 21 and 22 under ongoing high-speed solar wind influences.