ALERT – Geomagnetic K-index of 4 Alert issued on October 11

A Geomagnetic K-index of 4 Alert was issued on October 11, 2025, by the NOAA Space Weather Prediction Center. The threshold was reached at 05:09 UTC and the alert is active for the synoptic period from 03:00 to 06:00 UTC. This alert indicates heightened geomagnetic activity.

Impacts are primarily expected poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations are possible in affected areas. Additionally, auroras may be visible at high latitudes, including locations such as Canada and Alaska.

The currently observed geomagnetic activity is linked to mildly enhanced interplanetary magnetic field conditions and slow solar wind, as stated in the latest forecast discussion. No Earth-directed coronal mass ejections have been detected. Increased geomagnetic activity is anticipated due to the influence of a recurrent, negative polarity coronal hole, with active conditions likely to persist through October 11 and a chance of G1 – Minor Geomagnetic Storm levels on October 12 and 13.