CO-ROTATING INTERACTION REGION: NOAA forecasters estimate a 30% chance of polar geomagnetic storms on Sept. 23-24 when a co-rotating interaction region (CIR) is expected to hit Earth's magnetic field. CIRs are transition zones between fast- and slow-moving solar wind streams. Solar wind plasma piles up in these regions, producing density gradients and shock waves that do a good job of sparking auroras.In all my years of visiting the SpaceWeather.com website every day, this is the first time I've read about a CIR. I'm drawn to the fact that CIRs are "transition zones between fast- and slow-moving solar wind streams," since that feels a lot like where we are right now, trying to decide which stream to jump into.
I guess we'll see what the "density gradients and shock waves" feel like, eh?