Moderate M1.1 solar flare erupts at 00:21 UTC on October 16, 2025

A moderate M1.1 solar flare erupted at 00:21 UTC on October 16, 2025.

Today’s flares include several M-class events reported in the forecast discussion, such as an M4.8 flare, M3.7 flare, a long duration M1.1 flare, M2.7 flare, and M2.4 flare, all occurring on October 15, 2025, with no new event reports for October 16, 2025 in the edited events file.

In 24 hours to 00:30 UTC on October 16, solar activity continued at moderate levels with several M-class solar flares observed. Notable events included an M4.8 flare at 04:15 UTC, M3.7 at 07:18 UTC, a long-duration M1.1 flare peaking at 14:10 UTC, a long-duration M2.7 flare at 22:28 UTC, and an M2.4 flare at 23:45 UTC, all on October 15. Associated coronal mass ejections were detected with some flares, and further analyses are underway to determine any Earth-directed components.

Minor to moderate (R1-R2) radio blackouts are likely through October 18, with a slight chance for an isolated R3 (Strong) event, due to continued elevated flare activity.

Active sunspot regions presently observed on the Earth-facing solar disk include AR 4246 (N22W56 – Beta-Gamma-Delta), AR 4248 (N07W27 – Beta-Gamma-Delta), AR 4250 (N07W21 – Alpha), AR 4252 (S13E28 – Beta), and AR 4254 (N10E60 – Alpha).

Over the past 24 hours, the greater than 2 MeV electron flux reached high levels, peaking at 2 850 pfu. The greater than 10 MeV proton flux remained at background levels. The greater than 2 MeV electron flux is expected to decrease to normal to moderate levels with the arrival of CMEs on October 16, rising again to moderate to high levels on October 17–18. There is a slight chance for a greater than 10 MeV proton event above the S1 – Minor level through October 18.

Solar wind parameters were slowly returning to nominal levels as the effect of a negative coronal hole high-speed stream waned. The total interplanetary magnetic field was at or below 6 nT, and solar wind speeds gradually decreased from about 550 km/s to 485 km/s. Solar wind conditions are expected to gradually wane over October 16 as this influence continues to subside, with disturbed conditions expected late on October 16 and through October 17 due to CME arrivals from earlier activity.

Geomagnetic field activity was quiet to unsettled with a single isolated active period. G2 – Moderate geomagnetic storm levels are likely late on October 16 in response to recent CMEs, with G1 – Minor geomagnetic storm activity likely to persist into October 17 and quieter conditions returning by October 18.