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Space Weather Alert - 12th May 2021

What Has Happened?

DSCOVR solar wind measurements showing the shock arrival (sharp jump in speed, magnetic field and density) around 05:50 UT, credit: DSCOVR (NASA).


A coronal mass ejection (CME) left the Sun on 9th May, associated with a filament eruption. A shock signature from this CME was observed in the ACE and DSCOVR satellite data at around 05:50 (UT) on 12th May and a sudden commencement was recorded at Earth just after 6:30 (UT) on the morning of the 12th May.

The geomagnetic field has been disturbed as a result and has reached STORM G3 conditions ( Click here for a description of the G-scales) already today. This was associated with a period of southward pointing interplanetary magnetic field (IMF, as measured in the solar wind). The IMF has since turned back northwards so geomagnetic activity is likely to wane, for the moment. However, further periods of southward IMF are possible, which could lead to some further STORM periods this evening (12th May).

Assuming clear, dark skies, there is a chance of seeing the aurora on the evening of 12th May. 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.

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.