A sudden impulse of 17 nT was observed at the Boulder magnetometer at 23:00 UTC on November 11, indicating the arrival of CME/s at Earth. The ACE spacecraft at L1 position recorded a sharp rise in solar wind speed from 464 km/s to 741 km/s at 22:12 UTC, accompanied by an increase in the interplanetary magnetic field (IMF) strength to 60 nT and a southward Bz component near -55 nT.
Geomagnetic field responded sharply with K-index of 4 at 00:19 UTC on November 12, increasing to G1 – Minor geomagnetic storm at 00:21 UTC, G2 – Moderate at 00:30 UTC, and G3 – Strong at 00:45 UTC.
G4 – Severe geomagnetic storming was observed starting at 01:22 UTC and lasting until about 03:10 UTC. Another period of G4 – Severe storming was observed from 03:46 to about 07:00 UTC, followed by G3 – Strong storming from about 09:00 UTC.
During G4 – severe geomagnetic storm conditions, impacts are primarily observed at geomagnetic latitudes poleward of 45°.
Power transmission systems may experience widespread voltage control problems, and protective devices can mistakenly trip out key components from the grid. Induced currents in long conductive structures, such as pipelines, intensify.
Spacecraft are exposed to surface charging, increased aerodynamic drag in low Earth orbit, and potential tracking and orientation difficulties.
Satellite-based navigation systems, including GPS, can experience significant degradation or complete loss of service for several hours.
High-frequency (HF) radio propagation becomes sporadic or is entirely blacked out while aurora can extend to unusually low latitudes, potentially visible as far south as Alabama and northern California.
“Infrastructure operators and authorities have been notified to take action to mitigate any possible impacts and for situational awareness,” SWPC said.
Our first experiment with a video explanation of the activity was well received, so here is an update as we continue into the overnight to morning hours. We will attempt another update later on Wednesday if warranted. Stay informed at pic.twitter.com/3QHpcMp0N3
— NOAA Space Weather Prediction Center (@NWSSWPC) November 12, 2025
Model analyses by SWPC indicated that the CME launched on November 9 would be followed by two additional, faster eruptions associated with major flares on November 10 and 11.
The November 9 CME, produced by an X1.7 flare, was modeled to arrive near 23:00 UTC on November 11, with subsequent impacts expected late on November 12 as the November 10 CME, associated with an X1.2 flare, and the November 11 CME, associated with an X5.1 flare, reach Earth.
Together, these eruptions are forecast to produce a sequence of elevated solar wind speeds exceeding 700 km/s and sustained geomagnetic storming extending through November 13.
By mid to late November 12, activity is expected to intensify again to G4 – Severe or greater levels with the arrival of the November 11 CME.
Geomagnetic storming is likely to persist through November 13 at G1 – Minor to G3 – Strong levels as CME activity continues. Conditions are forecast to decline to unsettled to G1 – Minor levels by November 14 as solar wind parameters gradually weaken.
Aurora watchers have reported vivid and widespread displays, with sightings confirmed well south of the usual auroral zones.
Observers documented visible aurora from Tennessee, Arkansas, Louisiana, and Florida, including along the Mississippi River just north of Natchez. These reports place the southernmost extent of visibility at unusually low latitudes for a G4 – Severe geomagnetic storm.
Further south, observers in Mexico reported visible aurora over several states, with particularly bright sightings documented as far south as Zacatecas.
In 24 hours to 00:30 UTC on November 12, the solar radiation environment showed notable enhancement following three consecutive major flares and associated CME activity. The greater than 2 MeV electron flux increased above high levels at 10:25 UTC on November 11, coinciding with a rise in high-energy proton flux that indicated contamination of electron measurements.
The greater than 10 MeV proton flux began to rise after 10:20 UTC on November 10, following the X1.2 flare at 09:19 UTC on November 10, reaching S1 – Minor radiation storm levels at 11:25 UTC on November 10.
After the X5.1 flare at 10:04 UTC on November 11, proton flux intensified further, exceeding S2 – Moderate levels at 12:25 UTC on November 11.
The greater than 10 MeV proton flux exceeded 1 000 pfu, reaching S3 – Strong radiation storm levels at 01:45 UTC on November 12.
Under S3 – Strong radiation storm conditions, passengers and crew in high-latitude, high-altitude flights may experience increased radiation exposure, and astronauts performing extra-vehicular activity are subjected to elevated radiation doses.
Spacecraft may experience single-event upsets in onboard systems, noise in imaging instruments, and minor efficiency losses in solar panels, while high-frequency radio communication over polar regions may experience significant degradation or episodic blackouts.
The greater than 2 MeV electron flux is forecast to remain at normal to moderate levels from November 12 to 14 as the CMEs from November 9 to 11 pass Earth. The greater than 10 MeV proton flux is expected to remain elevated above S1 – Minor to S2 – Moderate levels through November 13.
S1 – Minor levels are likely to persist on November 14 as particle flux gradually diminishes, provided no other enhancements take place.
Active Region 4274, responsible for this round of geomagnetic and radiation storming, still has ‘beta-gamma-delta’ magnetic configuration and is capable of producing more major eruptions, exceptional CMEs and new rounds of storming on Earth.
References:
1 Forecast Discussion – NOAA/SWPC – 00:30 UTC on November 12, 2025