Moderate M1.5 solar flare erupts at 01:28 UTC on October 17, 2025

A moderate M1.5 solar flare erupted at 01:28 UTC on October 17, 2025.

Today’s flares include an M1.5 solar flare from AR 4246 (peak at 01:28 UTC), a C8.0 flare from AR 4248 (peak at 05:54 UTC), and several minor C-class flares from AR 4246 throughout the day, including C6.7 (10:20 UTC), C6.5 (10:37 UTC), C7.2 (10:46 UTC), and C6.1 (12:06 UTC).

In 24 hours to 12:30 UTC on October 17, solar activity remained at moderate levels with multiple M-class and numerous C-class flares. Region 4246 was the primary contributor, producing several M1 flares. No Earth-directed CMEs were detected.

Minor to moderate R1 to R2 radio blackouts are likely through October 18, with a slight chance for an isolated R3 (strong) event, primarily due to activity from regions 4246 and 4248. Probabilities slightly decrease on October 19 as AR 4246 rotates off the visible disk.

Active sunspot regions presently observed on the Earth-facing solar disk include AR 4246 (N24W69 – Beta-Gamma-Delta), AR 4248 (N07W41 – Beta-Gamma), AR 4250 (N05W34 – Alpha), AR 4252 (S13E14 – Beta), AR 4254 (N10E46 – Alpha), AR 4255 (S08E38 – Beta), and AR 4256 (S16E66 – Beta).

Over the past 24 hours, the greater than 2 MeV electron flux reached high levels, peaking at 3 769 pfu, while 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 17 due to glancing CME influence, returning to high levels on October 18 and 19. There is a slight chance for a greater than 10 MeV proton event to exceed S1 – Minor levels through October 18.

Over the past 24 hours, solar wind parameters were nominal until 09:30 UTC when an enhancement occurred in the interplanetary magnetic field, potentially from a CME glancing blow from October 13 to 15. The total field increased from 6 to 12 nT and the Bz component turned southward between -3 and -9 nT. Solar wind speeds remained around 380 km/s. Further enhancements are possible through October 18, with a return to quieter conditions expected by October 19.

Geomagnetic field activity was at quiet to active levels. G1 – Minor geomagnetic storming is likely on October 17 due to further glancing CME effects, with unsettled to active geomagnetic conditions and a chance for G1 – Minor storming on October 18 as well. Activity levels are anticipated to decrease in the early part of October 19.