Geomagnetic storm update - 3rd September 2025
What Has Happened?
An abrupt shock in the solar wind speed around 21:02 UTC, 01 September marked the sudden storm commencement associated with this coronal mass ejection event (CME), first observed on 30 August. In the UK, geomagnetic activity reached STORM G2 - STORM G1 / minor storm conditions between 21:30 UT 01 September and 04:00 UT 02 September, approximately. The interplanetary magnetic field component Bz was only weakly southward (less than -28 nT) and did not persist for long periods, thus avoided any large geomagnetic storms.
Around 00:31 UTC on 03 September further minor storm periods were detected. The solar wind speed gradually dropped in throughout 03-September, signifying that the Earth has emerged from the magnetic cloud of the CME. No additional significant enhancements to geomagnetic activity are anticipated from this event.
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Glossary
- BGS
- The British Geological Survey is a geoscience research centre that is part of UK Research and Innovation (UKRI) and affiliated to the Natural Environment Research Council (NERC).
- CME or Coronal Mass Ejection
- The eruption of a portion of the outer atmosphere of the Sun into space, caused by rapid changes in its magnetic field. Often occurs along with a solar flare.
- Solar Wind
- The ever-present expansion of the Sun’s hot outer atmosphere into the solar system, which carries space weather within it.
- Magnetogram
- The variation, minute by minute, of the strength and direction of the Earth’s magnetic field. Measured in units of nano-Tesla (for the strength of the field) or in degrees (direction of the field).
