I hope you’ll have clear skies tonight to see a nice conjunction of Saturn and the almost-half moon in the southwestern sky at dusk. They’ll be fairly close, about 2½° apart, and worth a look. If you haven’t seen Saturn through a telescope lately, tonight’s pairing will serve as a reminder to look at the ringed planet yet another time before it departs the evening sky. Sure as sugar, it’s been drifting westward with the seasons and already getting too low for a good look after 9 p.m. local time.
Then get ready for a good shot at seeing the northern lights Wednesday night the 27th. High speed solar winds from a large coronal hole are joining forces with a CIR or corotating interaction region to set us up for a minor G1 geomagnetic storm starting tomorrow afternoon. It’s expected to amp up to a G2 or moderate storm by nightfall across the northern half of the U.S. and Canada.
What’s a CIR? When a high-speed solar wind, say from a coronal hole, interacts with an earlier, slow-moving stream, it enhances the strength of the magnetic field embedded in the material, making a CIR. When the bundle arrives at Earth, our magnetic defenses can get pounded almost as much as when the sun erupts with a CME or coronal mass ejection. Since coronal holes are common even around solar minimum, we’re never really out of the woods when it comes to the sun’s magnetic muster.