Solar Blast Could Trigger Bright Northern Lights Weds. night Dec. 9

 

Look at those whirls of hot plasma! These formed in the wake of a C-class solar flare in active region 2790 mid-morning (CST) on Dec. 7. The material is now on its way to Earth and could possibly spark a geomagnetic storm and auroras. The photo was made in far ultraviolet (UV) light by NASA's Solar Dynamics Observatory. NASA / SDO

A modest flare that occurred in sunspot group 2790 on Dec. 7 blasted a tsunami of solar ions toward planet Earth. The wave is expected to arrive late Weds. afternoon (Dec. 9) and initiate a minor or G1 geomagnetic storm that will intensify into a G3 or strong storm later that evening.

Sunspot group 2790, pictured here on Dec. 5, is no great shakes but somehow pulled off a big enough flare to stir excitement among aurora-watchers down here on Earth. Bob King

The arrival is coupled with material expelled from another source, a coronal hole, so we get the benefit of a double whammy. The latest space weather forecast predicts a G1 storm through about 9 p.m. CST followed by a steep increase in activity to G3 from 9 to around midnight. From midnight till dawn, activity will decline to G1 again. (Updated 12/9 at 4:15 p.m. — the storm is delayed and now expected to arrive Thursday, Dec. 10, beginning in the afternoon and continuing well into the night. It will reach G3 levels early, drop to G1 during the early evening hours and then increase to G2 closer to midnight.)

A massive wall of rayed curtains towers in the northern sky during the Aug. 26, 2018 auroral display. Bob King

This is the most exciting aurora forecast I've seen in a long time. Should it play out as anticipated, skywatchers could see the northern lights as far south as Illinois and Oregon. And because the moon is a crescent and doesn't rise until around 2:45 a.m. local time it won't brighten the sky and detract from the display.

To watch, find a place with an open view to the north. Start looking as early as nightfall, which begins around 6-6:30 p.m. for most locations. The aurora is often brightest and most active closer to midnight, so check regularly for activity. If you don't see anything at 6:30, go out again an hour later and then an hour after that. Displays sometimes have multiple peaks, too. Just when you think it's over, the show reconstitutes itself and explodes again! This is the reason aurora-watchers rarely get the sleep they need. 

I know one thing we do need right now — clear skies!

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