Aurora Bump Tonight, Storm Expected This Weekend Sept. 27-28

A cloud of suspended magnetized gas called a filament erupted in the sun’s atmosphere on Sept. 20 and send a cloud of material that may arrive to spark auroras tonight. Photo by NASA’s STEREO spacecraft. A disk blocks the sun so cameras can photograph the area around it without glare. NASA

The sun sneezed on Sept. 20 and blew a bunch of electrons and protons into space in a coronal mass ejection. That material is expected to arrive later this afternoon and evening and potentially spark a minor display of the northern lights. Skywatchers in the fringes of the northern U.S. and across Canada should be on the watch tonight from nightfall till around midnight. I suspect we’ll see a glow or possibly a bright arc low in the northern sky from northern Minnesota, Michigan and Wisconsin.

That’s just the warm-up act. A more powerful stream is en route from a giant magnetic hole in the sun’s corona. This is the same hole that kicked up the last significant aurora on Aug. 30-31. Remember that one? While it never filled the sky we saw all kinds of fascinating rays and glowing puffs plus an appearance by the aurora-lookalike STEVE. Now, not quite a month later — equal to one rotation of the sun — that same hole is facing our way again.

He’s back! The same hole you see here in this ultraviolet photo of the sun has returned to (we hope) wreak more beautiful havoc. NASA / SDO

In their 27-day forecast, space weather experts predict a Kp index of 6 at peak, equal to a moderate G2 geomagnetic storm. Kp indices are a marker of magnetic activity in the Earth’s ionosphere, the layer of atmosphere where the aurora makes its appearance. Kp numbers range from “0” for no activity to “9” for a massive event. A moderate storm would be visible as far south as the central U.S. For now, peak activity is expected Friday night (Sept. 27) and will continue through Saturday evening.

No moon will spoil the fun, so if the weather’s good tonight or coming this weekend, watch the sky. I’ll update if viewing times change.

The thick crescent moon and a touch of fall Monday morning about 9 a.m. Bob King

Have you guys noticed the moon in the morning sky lately? It’s been rolling through the constellations that the sun spends time in during the summer months, so it’s way up high during the morning hours in a full-blown daylight sky. Some have remarked how white it looks against the blue. The fall months, with their late sunrises, afford a great opportunity to see the moon’s waning phases. Those are all the phases that start AFTER full moon, when the moon slims from waning gibbous to last quarter to crescent.

A sugar maple shows off yesterday along the Superior Hiking Trail near Duluth. Bob King

It’s a crescent now and getting a little harder to see as it approaches the direction of the sun and its glare. We probably have one more morning of viewing, and then we’ll have to wait for the next round that runs from about Oct. 16-25. Try tomorrow (Sept. 25). Block the sun with your open hand and look about 5 fists to the right and above it for a pale sliver.