Minor C9.0 solar flare erupts at 23:30 UTC on October 17, 2025

A minor C9.0 solar flare erupted at 23:30 UTC on October 17, 2025.

Today’s flares include M1.5, M1.3, M1.2, M1.1, and M1.0 events from region 4246, with peak times at 01:28, 16:32, 16:58, 12:45, 19:05 and 14:32 UTC. Additional C-class flares were also recorded from regions 4246 and 4248.

In 24 hours to 12:30 UTC on October 17, solar activity remained at moderate levels, with continued M-class and several C-class flare activity from region 4246. Region 4248 was relatively quiet. No Earth-directed CMEs have been identified.

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 flare activity potential in regions 4246 and 4248. Event probabilities decrease slightly on October 19.

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, with a maximum flux of 3 769 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 17 before returning to high levels on October 18–19. There is a slight chance for greater than 10 MeV proton levels to exceed S1 – Minor thresholds through October 18.

Solar wind conditions were nominal until 09:30 UTC on October 17, with an enhancement in the interplanetary magnetic field possibly from prior CME effects. Total magnetic field increased from 6 to 12 nT, with Bz decreasing to values between -3 and -9 nT. Solar wind speeds stayed around 380 km/s. Further enhancements are possible through October 18 due to glancing CME influences, with more nominal conditions expected October 19.

Geomagnetic field activity ranged from quiet to active levels. G1 – Minor geomagnetic storming is likely on October 17 due to CME effects from events on October 12–13, with unsettled to active conditions and more G1 activity possible on October 18 as further CME effects impact the near-Earth environment into early October 19.