NOAA’s Space Weather Prediction Center’s (SWPC) three-day forecast, issued at 00:30 UTC on October 9, predicts a peak planetary Kp index of 6, corresponding to a G2 – Moderate geomagnetic storm.
At G2 geomagnetic storm levels, possible effects include voltage alarms in high-latitude power systems, satellite orientation corrections, and changes in atmospheric drag that affect satellite orbit predictions. High-frequency (HF) radio propagation can also fade at higher latitudes, while aurora could be visible as far south as New York and Idaho.
The CME’s influence is expected to give way to a negative polarity coronal hole high speed stream on October 10. Unsettled to active geomagnetic conditions are expected that day, including another G1 – Minor storm interval during 03:00–06:00 UTC period on October 11.
The geomagnetic field was quiet before the anticipated CME arrival, with the highest observed three-hour Kp during the preceding reporting period at 2, below geomagnetic storm levels.
Solar wind speed averaged approximately 350 km/s. The total interplanetary magnetic field ranged from 1 to 6 nT, while its north–south component, Bz, was weakly southward.
A separate eruption occurred on October 8, when solar active Region 4549 produced an M6.7 flare peaking at 15:48 UTC. The flare was accompanied by Type II and Type IV radio emissions and an extreme ultraviolet wave observed in GOES Solar Ultraviolet Imager imagery. SWPC was still analyzing the CME associated with that eruption at the time of this report.
The Type II radio emission produced an estimated speed of approximately 4 125 km/s, reported by the Sagamore Hill station of the U.S. Air Force Radio Solar Telescope Network. However, SWPC’s preliminary analysis of the CME indicated a speed closer to 900 km/s.
Region 4549 had a beta-gamma-delta magnetic configuration and was located at N10W29 at the time of eruption. Its leading and trailing sunspots were separating, while an east–west-oriented delta configuration continued to bisect the leading spots, increasing the potential for magnetic shearing.
The region remains the main expected source of further M-class flares through October 11. SWPC gives a daily 55% probability of R1–R2 (Minor–Moderate) radio blackouts and a 10% probability of R3 (Strong) or greater radio blackouts during that period.
Energetic electron levels were also elevated over the past 24 hours, with the greater than 2 MeV electron flux peaking at 11 336 particle flux units (pfu) at 12:50 UTC on October 8.
High electron flux is expected to persist early on October 9, then fall to normal or moderate levels following the anticipated CME arrival by midday UTC. Levels were forecast to remain below the high-flux threshold through October 11.
The greater than 10 MeV proton flux remained at background levels. SWPC gives a 10% probability of a proton event exceeding the 10 pfu threshold for an S1 – Minor solar radiation storm through October 11.
Additional solar wind enhancements remain possible from the October 8 CME.
References:
1 Forecast Discussion – NOAA/SWPC – Issued at 00:30 UTC on October 9, 2026