Alert – Geomagnetic K-index of 4 issued on April 18, 2026

A Geomagnetic K-index of 4 Alert was issued on April 18, 2026, with the threshold reached at 04:14 UTC. This alert covers the synoptic period from 03:00 to 06:00 UTC. The alert is currently active and was issued by NOAA’s Space Weather Prediction Center.

The primary area of impact for this alert is poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations can occur due to induced currents. In addition, auroras may be visible at high latitudes, including regions such as Canada and Alaska. These potential impacts are consistent with the NOAA Space Weather Scales for a K-index of 4.

The forecast discussion indicates that solar wind parameters are expected to become more enhanced early on April 18 due to the arrival of a corotating interaction region (CIR) followed by negative polarity coronal hole high speed stream (CH HSS) activity. Enhanced solar wind conditions are anticipated to persist through April 21, with geomagnetic field conditions expected to range from quiet to active levels early on April 18 and increase to G1-G2 (Minor-Moderate) geomagnetic storming levels later in the day.