Moderate M1.0 solar flare erupts at 07:53 UTC on December 20, 2025

A moderate M1.0 solar flare erupted at 07:53 UTC on December 20, 2025.

Today’s flares include a C1.2 flare at 00:59 UTC, a B8.8 flare at 03:40 UTC, a B8.0 flare at 04:10 UTC, two C1.3 flares at 05:22 UTC and 06:08 UTC, and a C1.2 flare at 05:42 UTC.

In 24 hours to 00:30 UTC on December 20, solar activity briefly reached moderate levels due to a single impulsive M1.0 flare. Region 4308 and 4310 decayed to plage, and no Earth-directed CMEs were observed.

Solar activity is forecast to remain at low levels with occasional C-class flares through December 22, 2025.

Active sunspot regions presently observed on the Earth-facing solar disk include AR 4305 (S25W0 – Alpha), AR 4307 (S15W0 – Beta), AR 4311 (N04W27 – Alpha), AR 4312 (N19E51 – Alpha), and AR 4313 (S14E16 – Alpha).

Over the past 24 hours, the greater than 2 MeV electron flux reached high levels, with a peak flux of 3 240 pfu. The greater than 10 MeV proton flux persisted at background levels. High electron flux is expected through December 21 before returning to normal to moderate levels. Proton flux is forecast to persist at background through December 22.

The solar wind environment reflected waning negative polarity coronal hole high-speed stream influences. Total field decreased from 5 nT to 2–4 nT, and Bz remained about ±5 nT. Solar wind speeds declined from around 670 km/s to about 500 km/s, with phi oscillations into the positive sector late in the period. Solar wind is forecast to remain mildly enhanced on December 20, return to background on December 21, and enhance again on December 22 due to recurrent positive polarity CH HSS influences.

Geomagnetic field activity was at quiet levels over the past 24 hours. Geomagnetic activity is expected to be quiet with a chance for isolated periods on December 20 as CH HSS effects diminish. Quiet conditions are expected to continue on December 21. G1 – Minor geomagnetic storming is likely on December 22 due to recurrent positive polarity coronal hole high-speed stream effects.