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Space Weather Alert - 23rd October 2020

What Has Happened?

EUV image from SDO satellite showing the large southern extension of the northern polar coronal hole  responsible for the anticipated storm events (black area of the Sun). Image from SDO (NASA).


Geomagnetic activity is expected to increase over the weekend due to the effects from various coronal holes in geoeffective positions. There are two extensions to the northern polar coronal hole, and another coronal hole centrally-positioned near the equator. On the previous rotation these coronal holes were responsible for geomagnetic activity reaching STORM G2. Statistically geomagnetic storms are more likely around the equinoxes, including September and October. The nature of the coronal holes has changed in the past month but there is still a good chance of further magnetic activity from these features.

Initially some ACTIVE periods are possible on Friday or Saturday (23-24th). From Sunday 25th October the solar wind speed is expected to increase further and it is possible we will reach STORM G1 level, and we can't rule out the possibility of activity up to STORM G2. These effects may persist into the start of next week.

The timing of coronal hole high-speed solar wind arrival can be often uncertain, but assuming clear, dark skies, there is a greater chance of seeing the aurora over the next few days. Those more northerly - Scotland, northern England and Northern Ireland - will have the better chance, if there are cloud-free skies.


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

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