K-index of 4 – Geomagnetic Storm Alert issued on October 17

A K-index of 4 – Geomagnetic Storm Alert was issued on October 17, 2025. The alert was triggered after the threshold was reached at 11:59 UTC, and the alert is valid for the synoptic period from 09:00 UTC to 12:00 UTC.

According to official information, areas primarily poleward of 65 degrees geomagnetic latitude may be affected. The main potential impacts include weak power grid fluctuations due to induced currents, and aurora may be visible at high latitudes such as Canada and Alaska. These impacts are consistent with minor geomagnetic storm conditions defined on the NOAA Space Weather Scales.

The event was linked to geomagnetic field activity that increased from quiet to active levels, attributed to the glancing effects of a coronal mass ejection (CME) that left the Sun between October 13 and 15. An enhancement in the interplanetary magnetic field was observed around 09:30 UTC on October 17, increasing the total field and causing the Bz component to turn further southward, all while solar wind speeds remained near 380 km/s. Forecasts indicate that unsettled to active geomagnetic conditions, with a chance for further G1 – Minor geomagnetic storm activity, may continue through October 18 due to ongoing CME influences.