Feb 21 forecast

[Sam Warfel]

While looking at the long-term KP index forecast, I noticed the prediction of KP=5 on Feb 21.  This interests me, KP=5 offers a potential of viewing for my area (Southern WI, US). 

I’m wondering how it can be predicted so far out. Is it because of the sun spinning, it comes back around at that time? How accurate is this forecast, or how likely is it to actually turn out to be less active than the predicted maximum?

I’m also wondering why, with active periods like this one or the several the past couple months, the first day of activity is usually the strongest.  It definitely seems like this is a consistent pattern, what causes this? So, in general, the first night of an active period is the best chance to look?

Thanks, sorry for so many questions   :P

[halojatapäivää]

There's been a long lasting coronal hole in the sun's northern hemisphere. The strongest effect was in late September (kp6-) but it has caused kp4 or kp5 roughly every 27 days or so when the sun has rotated once. You can see it from here: https://www.spaceweatherlive.com/en/archive/2020/09/26/coronal-holes.html

If you click "next rotation" you can see how it has developed. The first day is usually the strongest because the solar wind speed is slightly higher. Strongly negative bz tends to be more likely too so the solar wind leaks into the atmosphere more easily.

Edited February 5, 2021 by halojatapäivää