Geomagnetic storm forecast - 6^th August 2025

What Has Happened?

We are expecting an increase in geomagnetic activity on Friday and throughout the weekend due to the combined effects of a coronal hole high speed stream (HSS) and the arrival of an Earth-directed Coronal Mass Ejection (CME).

An M4.5-class solar flare occurred in the centre of the solar disk on 5^th August 2025 at 15:53 UT. This flare produced a CME that is traveling toward Earth at a moderate speed of over 500 km/s. Additionally, the high speed stream from a recurrent coronal hole (CH69) is due to arrive on Friday. The combined effect of the CME and the HSS is expected to enhance geomagnetic activity on Friday 8^th August 2025 up to minor geomagnetic storm level or G3 on the NOAA scale.

Assuming clear dark skies, there is an increased chance of seeing the aurora Friday and Saturday night, August 8^th-9^th. Those in Scotland, northern England and Northern Ireland have the best chance if the weather is favourable.

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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.

Coronal Hole

A region in the Sun’s outer atmosphere (corona) where hot material can flow unrestrained by its magnetic fields out into space.

High Speed Stream

A fast moving stream of solar wind, responsible for magnetic storms.

Solar Flare

Energy released by the explosive reorganisation of magnetic fields within the Sun's atmosphere.