Two big, naked-eye sunspot groups are putting on a splendid show this week. We're also in the crosshairs for a strong geomagnetic storm and possible auroras.

Wait a minute. Giant sunspots, multiple M-class flares, and a coronal mass ejection forecast to send the magnetosphere into a tizzy of Northern Lights? Wasn't the Sun supposed to be easing toward solar minimum?

Last Saturday, a solitary sunspot metastasized into a sprawling cluster big enough to see with the naked eye and solar filter in just 24 hours. Named Active Region (AR) 2673, it grew rapidly in magnetic complexity. Most sunspot groups are bipolar, like the two poles of a horseshoe magnet; one end of the group is magnetic north, the other end magnetic south, with their polarities clearly separated. AR 2673 developed a potentially explosive Beta-Gamma-Delta structure, where bits of dark umbra of opposite polarity mingle close together inside a spot's penumbra.

In the broiling, convective environment of the Sun's photosphere, their proximity increases the chances they'll reconnect — positive to negative, negative to positive — and release their pent up magnetic energy as powerful solar flares. That's exactly what happened Monday, when no fewer than seven moderate or M-class flares erupted inside the group followed by five more on Tuesday.

During one of these flares, AR 2673 blasted a coronal mass ejection (CME) into space in Earth's direction. When it arrives later this morning (September 6th), space weather forecasters expect it to couple with our planet's magnetic field and send a torrent of high-speed electrons and protons into the upper atmosphere to spawn moderately-strong to strong (G2 to G3) geomagnetic storms.

You know what that means? A good shot at seeing the aurora borealis from the northern border states to as far south as Illinois and Oregon. While timing couldn't be worse — it's full Moon and western skies filled with smoke — a strong storm would likely still show up as bright arcs or balletic rays dancing across the northern sky. If AR 2673 continues spouting flares, auroras could also appear later in the week, when the Moon won't be as much of a problem. That's why I'd advise you to keep a lookout through the weekend.

Auroras or not, the Sun's looking lively these days in both white light and H-alpha. Another more benign but no less impressive sunspot group, AR 2674, has been "crawling" across the disk like a large caterpillar with a prominent, naked-eye leader spot and two large "back legs."

Still have your eclipse glasses? I hope you didn't make the mistake my mom did and toss them out after the eclipse, thinking they were for one-time use. I've been watching the progress of both AR 2673 and the leader spot of AR 2674 as they've inched across the rotating solar disk. Both appear as dark, round blemishes on an otherwise pristine Sun and should remain visible for another couple days. Seeing naked-eye sunspots reminds us that the ancient Chinese astronomers also used their unaided vision to record the comings and goings of sunspots; their first observations reach back to as early as the 4th century B.C.

Large regions of the western and central U.S. have been under a veil of smoke haze from forest fires in Oregon, Washington, and Canada throughout the summer. On Sunday night, smoke so attenuated the near-setting Sun, I could see the spots directly without a filter.