Moderate M1.2 solar flare erupts at 06:39 UTC on October 18, 2025

A moderate M1.2 solar flare erupted at 06:39 UTC on October 18, 2025.

Today’s flares include an M1.0 flare from Region 4246 peaking at 00:40 UTC, an M1.1 flare from Region 4246 peaking at 02:39 UTC, and a C9.9 flare from Region 4246 peaking at 06:05 UTC.

In 24 hours to 00:30 UTC on October 18, solar activity increased to high levels due to numerous M-class flares. Some sunspot decay was observed in active regions, with no Earth-directed coronal mass ejections detected.

Minor to moderate R1 to R2 radio blackouts are likely through October 18, with a slight chance for an isolated R3 event due to ongoing flare potential. Probabilities decrease on October 19 and 20 as active regions rotate beyond the limb.

Active sunspot regions presently observed on the Earth-facing solar disk include AR 4246 (N24W81 – Beta-Gamma-Delta), AR 4248 (N07W54 – Beta-Gamma), AR 4250 (N04W45 – Alpha), AR 4252 (S13E01 – Beta), AR 4254 (N11E33 – Alpha), AR 4255 (S08E26 – Beta), AR 4256 (S15E52 – Beta), and AR 4257 (S08E75 – Alpha).

Over the past 24 hours, the greater than 2 MeV electron flux reached high levels, with a peak of 3 330 pfu observed at 17:00 UTC on October 17. The greater than 10 MeV proton flux remained at background levels. The electron flux is expected to decrease to normal to moderate levels on October 18 due to glancing CME effects, with a slight chance for a greater than 10 MeV proton event above S1 – Minor levels.

During the past 24 hours, solar wind parameters were at nominal levels until an enhancement occurred in the interplanetary magnetic field at 09:30 UTC on October 17, likely due to glancing effects from a CME between October 13 and 15. Total field values increased, and the Bz component reached up to -9 nT. Solar wind speeds stayed near 380 km/s. Additional enhancements in solar wind are anticipated through October 18 due to lingering CME influences, with a transition into a negative polarity coronal hole high-speed stream expected on October 19.

Geomagnetic field activity was at quiet to unsettled levels over the past 24 hours. Unsettled to active geomagnetic conditions, with a chance for a G1 – Minor storm, are expected on October 18 due to any glancing CME impacts. These activity levels may persist into early October 19, followed by unsettled to active conditions from a negative polarity CH HSS.