ALERT: Geomagnetic K-index of 4 Alert issued on October 15

A Geomagnetic K-index of 4 Alert was issued on October 15, 2025, by the NOAA Space Weather Prediction Center. The alert was triggered at 02:59 UTC, covering the synoptic period from 00:00 to 03:00 UTC. The Geomagnetic K-index reached a value of 4, indicating unsettled to active geomagnetic conditions. The alert remains active as of the time of issuance.

Potential impacts from this level of geomagnetic activity are primarily expected in areas poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations may occur in these regions. In addition, auroras may become visible at high latitudes, such as in Canada and Alaska, during this period of increased geomagnetic activity.

According to the latest forecast discussion issued on October 15, 2025, solar wind parameters are gradually returning to nominal levels as the influence of a negative coronal hole high speed stream (CH HSS) wanes. The geomagnetic field is forecast to remain unsettled to active until late on October 15, with more significant storming conditions possible on subsequent days due to the arrival of coronal mass ejections (CMEs) from active region 4246. No new Earth-directed CMEs were detected during the period leading up to the alert.