Moderate M1.3 solar flare erupts at 06:58 UTC on October 18, 2025

A moderate M1.3 solar flare erupted at 06:58 UTC on October 18, 2025.

Today’s flares include an M1.0 event from AR 4246 (peak 00:40 UTC), an M1.1 event from AR 4246 (peak 02:39 UTC), and several C-class flares including a C2.9 at 02:09 UTC, a C9.5 at 02:24 UTC, and a C9.9 at 06:05 UTC, all from AR 4246.

In 24 hours to 00:30 UTC on October 18, solar activity increased to high levels due to numerous M-class flares. Region 4246 is responsible for most of this activity as it moved toward the western limb. No Earth-directed coronal mass ejections have been observed during this period.

Minor to moderate (R1 – Minor to R2 – Moderate) radio blackouts are likely through October 18, with a slight chance for an isolated R3 – Strong event, mainly due to the flare potential of active regions 4246 and 4248. Probabilities are expected to decrease as region 4246 rotates beyond the solar limb on October 19–20.

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, greater than 2 MeV electron flux reached high levels with a maximum of 3 330 pfu. 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 of a greater than 10 MeV proton event above S1 – Minor levels through the day. High electron flux is likely to return on October 19–20.

During the past 24 hours, solar wind conditions were nominal until an enhancement in the interplanetary magnetic field occurred at 09:30 UTC on October 17, likely due to a glancing CME from October 13–15. The total field increased to 14 nT, with solar wind speeds remaining near 380 km/s. Enhancements are possible through October 18 due to CME influences, followed by a transition into a negative polarity coronal hole high speed stream 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 possible glancing CME effects. These activity levels may continue into early October 19, followed by unsettled to active conditions as a negative polarity coronal hole high speed stream arrives.