Moderate M1.3 solar flare erupts at 14:08 UTC on October 16, 2025

A moderate M1.3 solar flare erupted at 14:08 UTC on October 16, 2025. Today’s flares include a M1.1 event (began 00:17 UTC, peaked 00:21 UTC, ended 00:24 UTC, Region 4246) along with several C-class events sourced mainly from Region 4246.

In 24 hours to 12:30 UTC on October 16, solar activity continued at moderate levels due to M-class flare activity. Notable flares included a long duration M1.1 event, as well as multiple C-class events from two active regions. No X-class flares were detected.

Solar activity forecast: Minor to moderate (R1–R2) radio blackouts are likely through October 18, with a slight chance for an isolated R3 (Strong) event related to the current and potential flare activity of active regions 4246 and 4248.

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 with a maximum flux of 2 850 pfu. The greater than 10 MeV proton flux remained at background values. The greater than 2 MeV electron flux is expected to decrease to normal to moderate levels on October 16 with CME arrivals and rebound 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 slowly returned to nominal levels as the negative coronal hole high-speed stream (CH HSS) influence waned. The total interplanetary magnetic field stayed at or below 6 nT, and the Bz component ranged between +3 and –4 nT. Solar wind speeds gradually decreased from about 520 km/s to 450 km/s. Solar wind parameters are expected to continue gradually waning during October 16 as the CH HSS influence reduces. Disturbed solar wind conditions are anticipated late on October 16 through October 18, due to CME arrivals from October 11–13 and October 15.

Geomagnetic field activity was mostly quiet during the past 24 hours. Geomagnetic field activity is likely to reach G2 – Moderate storm levels late on October 16 in response to CME arrivals, with G1 – Minor storm conditions possible through October 17–18 related to ongoing CME influences.