Solar wind speeds increased from 320 km/s to around 650 km/s after 23:00 UTC on September 14, consistent with the arrival of a corotating interaction region (CIR) ahead of the CH HSS.
G1 – Minor geomagnetic storm threshold was reached at 23:47 UTC, followed by G2 – Moderate conditions by 02:10 UTC. Impacts at this level include power grid fluctuations, satellite orientation irregularities, and degraded HF radio propagation at high latitudes.
Geomagnetic conditions peaked at 02:59 UTC with G3 – Strong storming. Possible impacts at G3 geomagnetic storm include power system voltage irregularities, false alarms on protection devices, spacecraft charging and drag, intermittent satellite navigation problems, and HF radio blackouts.
Dazzling aurora timelapse over Mill Pond late Sunday night between 10:52 PM and 11:41 PM ET (0252-0341 UTC).
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September 14, 2025
Alton, New Hampshire@TamithaSkov pic.twitter.com/nm3S6i5BED— Rob Wright Images (@RobWrightImages) September 15, 2025
This activity caused auroral displays to expand well into mid-latitudes, reaching as far south as Pennsylvania, Iowa, Oregon, and confirmed sightings in Texas.
The storm subsided within an hour, with conditions returning to G1 – Minor by 03:32 UTC. As of the latest SWPC updates, geomagnetic activity is fluctuating near G1 – Minor level.
Below is a selection of aurora photographs captured during the peak of the event.
The storming was caused by a negative polarity coronal hole high-speed stream that enhanced the solar wind environment, coupled with possible influence of a coronal mass ejection (CME) launched on September 11.
According to the SWPC Forecast Discussion issued at 00:30 UTC on September 15, solar activity remains low with primarily C-class flares from newly emerging regions.
Multiple CMEs were observed off the east following a series of C-flares from Region 4217, and a filament eruption near S23E68 on September 14. However, analysis indicates that no CMEs had Earth-directed components.
The greater than 2 MeV electron flux reached high levels on September 14, peaking at 1 570 pfu at 20:00 UTC, while the >10 MeV proton flux remained at background values. SWPC expects the electron flux to stay at high levels on September 15 before declining to normal to moderate levels during September 16–17. Proton flux is forecast to persist at background through the same period.
Geomagnetic activity is expected to remain elevated, with active to storm-level conditions possible through September 17 as CH HSS influence persists.
