Coronal Hole Promts Aurora Storm Watch for October 22-23

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Northern Lights Now – SWPC has issued a G1 geomagnetic storm watch for October 22nd and 23rd due to the enhanced magnetic fields expected as a high speed wind stream arrives at Earth. The high winds are the result of a coronal hole pointed directly towards Earth on October 18th and 19th. The watch means it’s possible that KP values could exceed 4.67 at some point in time on each of the two days the watch is in effect. This same coronal hole was responsible for two periods of G1 storming on September 25th. Here’s an image of the coronal hole:

Small coronal hole pointed toward Earth on October 19
Small coronal hole pointed toward Earth on October 19

The current forecast shows the impact of this storm arriving in two waves. First, at onset there may be a shock as the high-speed wind front arrives at Earth. Later on the 23rd, another period of higher KP is expected as the cumulative effects of the high solar wind enhance the magnetosphere’s sensitivity to any disturbances traveling on the wind. In this second period, any prolonged negatively oriented Bz would push the KP higher again. That means the exact timing of the second wave will be harder to predict. Aurora hunters will need to watch the data to know when and if to go out – or as this recent Twitter meme suggests: know when to put your pants on. Here are the current predicted timings from the NLN AuroraCast:

NLN AuroraCast shows two periods of G1 storming predicted, one on the 22nd and another on the 23rd
NLN AuroraCast shows two periods of G1 storming predicted, one on the 22nd and another on the 23rd

Looking ahead a little, it’s possible to see the edges of the next coronal hole coming into view in the north and east. This is a return of the coronal hole that produced Strong aurora from September 27 to 29. The Sun rotates about once every 28 days, so this means we can expect additional geomagnetic storm watches to be posted over the next couple of days for Sept 24-26. Stay tuned for those watches too.

Happy Hunting!