Minor C8.0 solar flare erupts at 21:54 UTC on October 18, 2025

A minor C8.0 solar flare erupted at 21:54 UTC on October 18, 2025.

Today’s flares include several M-class and C-class solar flares. Notable events are M1.0 at 00:40 UTC from region 4246, M1.1 at 02:39 UTC from region 4246, M1.2 at 06:39 UTC from region 4246, M1.3 at 06:58 UTC from region 4246, and M1.5 at 10:51 UTC from region 4246. Multiple C-class flares occurred, with the strongest being C9.9 at 06:05 UTC from region 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 showed intermediate spot decay as it approached the west limb, while regions 4248, 4256, and 4257 were either quiet or showed minor changes.

Minor to moderate (R1-R2) radio blackouts are likely through October 18, with a slight chance for an isolated R3 (Strong) event. Probabilities decrease slightly on October 19–20 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 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 expected to decrease to normal to moderate levels on October 18 due to glancing CME effects, and then return to high levels on October 19–20. There is a slight chance for a greater than 10 MeV proton event above S1 – Minor thresholds through October 18.

Solar wind parameters were nominal until 09:30 UTC on October 17, when interplanetary magnetic field enhancements were observed, likely due to glancing CME effects from October 13–15. The total magnetic field increased to 14 nT after 20:20 UTC, with solar wind speeds near 380 km/s. Further enhancements in the solar wind are possible through October 18 due to these CME influences, followed by a transition to a negative polarity coronal hole high speed stream on October 19.

Geomagnetic field activity was at quiet to unsettled levels. Unsettled to active geomagnetic conditions, with a chance for G1 – Minor storming, are expected on October 18 due to glancing CME effects, carrying over into early October 19. A transition to a negative polarity coronal hole high speed stream may sustain active conditions on October 19.