ALERT: Geomagnetic K-index of 4 Alert issued on September 27

A Geomagnetic K-index of 4 Alert was issued on September 27, 2026, indicating heightened geomagnetic activity for the synoptic period from 00:00 UTC to 03:00 UTC. The alert was issued by NOAA’s Space Weather Prediction Center at 00:40 UTC.

The potential impacts are primarily confined to regions poleward of 65 degrees Geomagnetic Latitude. Weak power grid fluctuations can occur due to induced currents in these areas. In addition, aurora may be visible at high latitudes, such as Canada and Alaska. This level of geomagnetic activity is consistent with minor space weather effects as described by NOAA’s space weather scales.

According to the latest forecast discussion, the geomagnetic activity is a result of lingering but weakening influences from a coronal hole high speed stream (CH HSS). The solar wind environment was mildly enhanced, with declining wind speeds and field strengths. No Earth-directed coronal mass ejections (CMEs) were detected, and solar activity overall remained at low levels.