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Space Weather Alert - 07 September 2017

What Has Happened?

Image of the Sun's corona showing the CME. The Sun is behind the occulting disc. (SOHO NASA/ESA)

Image of the Sun showing the M5.5 flare. (SDO NASA)

Plot of the solar X-ray flux from the 5th of September showing an increase due to the long-duration M-class flare around 2033UT on the 4th of September



A full halo Coronal Mass Ejection (CME) associated with a long duration M-class (Moderate) solar flare, which peaked at M5.5 around 20:33 UT, was observed on the evening of the 4th of September from active region AR2673 which is currently close to the centre of the solar disc.

This CME is expected to arrive at Earth early on the morning of the 7th of September bringing geomagnetic STORM conditions, although the precise arrival time cannot be confirmed. Periods of up to STORM G3 are possible with an average level of at least STORM G1 which is likely to continue throughout the day and into Friday the 8th.

Solar wind speed is currently somewhat elevated due to the waning influence of a northern polar coronal hole which may contribute to the enhancement of geomagnetic activity.

Assuming clear dark skies, and that the geomagnetic field is suitably disturbed, there is an increased chance of seeing the aurora. In the UK, those in Scotland, northern England and Northern Ireland may have the best opportunities.


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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.