G1 – Minor Geomagnetic Storm Alert issued on October 21

A G1 – Minor Geomagnetic Storm Alert was issued on October 21, 2026, after the geomagnetic K-index reached 5 at 23:59 UTC. This alert corresponds to the NOAA Space Weather Scale for G1 – Minor geomagnetic storms and applies to the synoptic period from 21:00 to 24:00 UTC. The warning remains active as of the time of issue at 00:03 UTC on October 22, 2026.

Potential impacts from this event include weak power grid fluctuations in areas poleward of 60 degrees geomagnetic latitude. Minor impacts are possible for satellite operations, and auroras may be visible at high latitudes—potentially extending to the northern tier of the United States, such as northern Michigan and Maine. These impacts align with the expected effects of a G1 – Minor geomagnetic storm according to NOAA’s official classification.

The alert was triggered by enhanced geomagnetic activity resulting from coronal hole high speed stream (CH HSS) effects. During the preceding period, the solar wind showed gradual increases in speed and sustained southward magnetic field components, both contributing to increased geomagnetic activity. No Earth-directed coronal mass ejections were observed. Solar activity otherwise remained low, with only several C-class flares reported.