Geomagnetic storm reaches G3 levels after March 18 CME impacts Earth

A strong G3-level geomagnetic storm occurred late on March 20 into early March 21, 2026, following the impact of a coronal mass ejection (CME) that left the Sun on March 18. The storm intensified after at least two CME structures arrived at Earth, with solar wind speeds reaching approximately 567 km/s and the interplanetary magnetic field (IMF) turning strongly southward to −28 nT. This configuration facilitated efficient coupling between the solar wind and Earth’s magnetic field, driving geomagnetic activity into the G3 – Strong range. The NOAA Space Weather Prediction Center (SWPC) reported that the first CME arrival was detected around UTC on March 20, followed by a second later the same day. The total IMF peaked at 36 nT during the event. Such geomagnetic storms can disrupt space-based systems by increasing atmospheric drag on satellites, degrade high-frequency radio communications and satellite navigation, and necessitate operational adjustments in power grids at higher latitudes to maintain stability. The storm also expanded auroral visibility to mid-latitude regions, with reports of northern lights observed in areas such as Vernon, British Columbia. This geomagnetic storm coincided with the March equinox, a period when the alignment between Earth’s magnetic field and the IMF typically enhances geomagnetic coupling, often leading to stronger storm responses even under moderate solar activity. Although solar activity remained low with minimal sunspot development and no significant flares, the CME impacts and the seasonal factor combined to produce the observed storm intensity. Forecasts from SWPC indicate that geomagnetic activity is expected to gradually decline as the CME effects wane through March 22. However, a coronal hole high-speed stream (CH HSS) is anticipated to influence the solar wind environment, potentially sustaining minor G1-level geomagnetic conditions into March 22 and keeping unsettled to active space weather through March 23. Solar activity overall remains low, with no Earth-directed CMEs currently expected.