ALERT – Geomagnetic K-index of 4 Alert issued on September 14

A Geomagnetic K-index of 4 Alert was issued by NOAA’s Space Weather Prediction Center (SWPC) at 18:02 UTC on September 14, 2026. The alert indicates geomagnetic activity reached an active threshold (K-index of 4) at 17:43 UTC, during the synoptic period from 15:00 to 18:00 UTC. The alert is currently active and primarily concerns regions poleward of 65 degrees geomagnetic latitude.

The potential impacts outlined by SWPC include weak power grid fluctuations that could be observed in the affected high-latitude areas. Additionally, aurora may be visible at high latitudes such as Canada and Alaska. Impacts are not expected to extend beyond the high-latitude regions for this level of geomagnetic activity. The alert corresponds to the active level on the NOAA Space Weather Scale.

The present geomagnetic activity is associated with negative polarity coronal hole high speed stream (CH HSS) effects anticipated to continue through September 16. Solar wind parameters remained mostly at background levels with some minor disturbances recorded, and the geomagnetic field was quiet prior to the threshold being met. As stated in the official forecast, unsettled to active geomagnetic conditions are expected to persist, with a chance for isolated G1 – Minor Geomagnetic Storm periods by September 15 and 16.