K-index of 4 – Geomagnetic K-index Alert issued on October 28

A Geomagnetic K-index of 4 Alert was issued by NOAA’s Space Weather Prediction Center on October 28, 2025, at 15:01 UTC. The alert indicates that the geomagnetic K-index reached a value of 4 at 14:51 UTC during the synoptic period from 12:00 to 15:00 UTC, signifying increased geomagnetic activity.

Potential impacts from this level of geomagnetic activity are expected primarily in areas poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations may occur due to induced currents, and aurora may be visible at high latitudes such as Canada and Alaska. These impacts are consistent with the NOAA Space Weather Scale for this level of geomagnetic disturbance.

The latest forecast discussion indicates that the elevated geomagnetic activity is related to the influence of a positive polarity coronal hole high-speed stream (CH HSS) impacting Earth’s environment. Solar wind speeds increased from 350 km/s to near 450 km/s over the past 24 hours, with unsettled geomagnetic conditions recorded. No significant solar flares or Earth-directed coronal mass ejections were detected during this period. Geomagnetic activity is expected to continue at similar levels through October 30, 2025.