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Space Weather Alert Update - 8th September 2017

What Has Happened?

Solar wind data showing the CME arrivals of the two CMEs. (Data: NOAA DSCOVR)

Chart of planetary Kp, a measure of global geomagnetic activity. This reached Kp8, or STORM G4 classification.

Magnetogram for BGS Lerwick Magnetic observatory over the 7th - 8th September 2017.



The coronal mass ejection from the 6th September, associated with the X9.3 solar flare, arrived earlier than expected, overnight on 7th/8th September. The impact on the Earth's magnetosphere was recorded at BGS's magnetic observatories. The magnetic field began to strengthen from 23:00 UT (00:00 BST). Geomagnetic activity was high. Globally this reached a peak of Kp=8 STORM G4 levels which sustained for around 6 hours.

In the UK geomagnetic activity was greatest at our most northern observatory in Lerwick, Shetland Isles. The local K reached K=9, STORM G5 levels, which is the highest value in this activity scale. The field also varied rapidly - at one point the compass direction (declination) swung by more than 3 degrees in 2 minutes!

The auroral oval broadened and stretched southwards and aurora sightings have been reported across Scotland. Many areas were affected by cloud but those on the east coast were fortunate to find the clouds cleared in time for a spectacular show.

Although the initial impact has now passed, the solar wind remains elevated and energised so there will continue to be some chance of further auroral displays over the weekend depending on the nature of the solar wind (impossible to predict!).


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The British Geological Survey is one of the Natural Environment Research Council's Research Centres.

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.

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

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

Solar Wind
The ever-present expansion of the Sun’s hot outer atmosphere into the solar system, which carries space weather within it.

Sunspot/Active Region
A region of intense magnetic field in the Sun's visible outer atmosphere often associated with flares and CMEs.