Solar activity reached high levels on September 28, with multiple M-class flares from Region 4232. An impulsive M6.4 flare erupted from Region 4232 at 08:43 UTC on September 28, launching a non-Earth-directed CME. Later that day, the same region also produced a C7.4 flare.
Region 4232 generated another CME-producing flare at 01:45 UTC on September 29, an impulsive M3.6 event. The associated CME was observed in SOHO LASCO coronagraph imagery beginning at 02:12 UTC, with trajectory modeling still in progress.
NOAA’s Space Weather Prediction Center (SWPC) forecasts solar activity to stay at moderate levels, with about a 55% chance for additional M-class flares through October 1 and a 10% chance for an X-class flare.
Energetic particle flux was stable in 24 hours to 12:30 UTC on September 29. The greater than 2 MeV electron flux was at moderate levels, while the greater than 10 MeV proton flux remained at background. Both are forecast to persist at same levels through October 1.
Solar wind parameters reflected weak influence from a negative polarity coronal hole high-speed stream (CH HSS). Total magnetic field strength peaked at 15 nT, with the Bz component turning southward after 20:00 UTC on September 28 and reaching −13 nT.
Wind speeds ranged from 375 to 450 km/s, with the interplanetary magnetic field oriented in the negative sector.
The geomagnetic field was at quiet to active levels. Forecasts indicate unsettled to isolated G1 – Minor storm conditions on September 29 under continued CH HSS influence, followed by mostly quiet conditions on September 30 and October 1.
References:
1 Forecast Discussion – NOAA/SWPC – September 29, 2025 at 00:30 UTC
2 Forecast Discussion – NOAA/SWPC – September 29, 2025 at 12:30 UTC