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Space Weather Alert - 3rd November 2021

What Has Happened?

Coronagraph images showing the halo CME from 2nd Nov. An earlier CME can also be seen in the bottom right of the image. Coronagraph credit: SOHO/LASCO (ESA/NASA), gif made using helioviewer.org.

GOES X-ray flux showing the M1.7 class solar flare, starting just after 2:00 on the 2nd Nov (credit: NASA).


A full-halo coronal mass ejection (CME) left the Sun early on 2nd Nov, associated with an M-class solar flare. This CME is directed towards the Earth and we expect it to arrive late on the 3rd or early on 4th Nov.

There have also been several more CMEs in the past few days, which might have some earthward component. There is a chance that some or all of these CMEs will interact with each other, increasing the chance for enhanced geomagnetic activity. This could lead to some periods of STORM conditions following the arrival, and throughout the 4th Nov.

Assuming clear, dark skies, there is a chance of seeing the aurora tonight (3rd) and early tomorrow (4th). Those in Scotland, northern England and Northern Ireland have the better chance if the weather is favourable.


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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.

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

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).

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