Moderate M1.0 solar flare erupts at 00:40 UTC on October 18, 2025

A moderate M1.0 solar flare erupted at 00:40 UTC on October 18, 2025.

Today’s flares include numerous M-class flares, as solar activity increased to high levels. However, there are no individual flare event reports available for October 18, 2025, as of 01:02 UTC.

In 24 hours to 00:30 UTC on October 18, solar activity increased to high levels due to multiple M-class flares. Sunspot region 4246 experienced some decay as it neared the western limb. Regions 4248 and 4256 were generally quiet, with region 4256 exhibiting minor penumbral growth. A new sunspot group, region 4257, was numbered this period. No Earth-directed coronal mass ejections were observed.

There is a likelihood of minor to moderate (R1-R2) radio blackouts through October 18, with a slight chance for an isolated strong (R3) event due to remaining flare potential. These probabilities lessen after October 18 as region 4246 rotates off the visible disk.

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 maximum flux of 3 330 pfu at 17:00 UTC on October 17. The greater than 10 MeV proton flux remained at background levels. The greater than 2 MeV electron flux is predicted to decrease to normal to moderate levels on October 18 before returning to high levels on October 19 and 20. There is a slight chance for an S1 – Minor solar radiation storm through October 18.

Solar wind conditions were nominal until 09:30 UTC on October 17, when an increase in the interplanetary magnetic field occurred, likely due to previous coronal mass ejection (CME) effects. The total field strength rose to 14 nT after 20:20 UTC. Solar wind speed remained near 380 km/s. Further enhancements are anticipated through October 18 due to glancing CME influences, followed by entry into a coronal hole high-speed stream on October 19.

The geomagnetic field was quiet to unsettled over the past 24 hours. Unsettled to active geomagnetic conditions with a chance for G1 – Minor storming are expected on October 18, associated with possible glancing impacts from CMEs. These conditions may persist into early October 19, with additional activity possible as the negative polarity coronal hole high-speed stream arrives.