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Astro Bob: Strong geomagnetic storm, auroras forecast Aug. 17-18

A pair of solar blasts are expected to punch up bright auroras across the much of the upper U.S. and Canada Wednesday night.

Aurora spikes
Parallel spikes of northern lights spear the northern sky during a moderate geomagnetic storm in March 2021. Space weather scientists expect an even stronger event starting Wednesday night, Aug. 17 and continuing through the night.
Contributed / Bob King
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Wow, this looks good. We have a solid forecast for northern lights Wednesday night through Thursday dawn, August 17-18. The first wave of the storm hit earlier this morning, with the grand slam expected to arrive early Wednesday night.

Early on August 14, the sun expelled a blast of plasma (electrons and protons) into space in the direction of the Earth called a CME. It's expected to arrive today and tonight and fire up extensive auroras. A metal disk covers the sun in this photo taken by the Solar and Heliospheric Observatory (SOHO).
Contributed / NASA, ESA

Solar forecasters point their collective finger at a CME (coronal mass ejection) that erupted back on August 14 as the primary cause, amplified by a recent coronal hole, a high-speed wind of material streaming from a gap in the sun's atmosphere.

NOAA's Space Weather Prediction Center (SWPC) forecasts a strong geomagnetic storm reaching the G3 level on a 1 to 5 scale of increasing intensity. While that won't pose a threat to power grids and satellites it does mean that folks living as far south as Illinois and Oregon may finally get their chance to see a northern lights show.

Solar wind
This is a prediction model showing the impact of the CME (red-yellow arc) at Earth (green dot) around midnight, August 17. The red and blue dots on either side of the Earth are the sun-observing satellites STEREO-A and STEREO-B, respectively.
Contributed / NASA, WSA-ENLIL

Aurora is likely to show as soon as evening twilight ends across northern Maine, Minnesota, Michigan, Wisconsin and North Dakota. It should intensify after 10 p.m. local time and remain strong through 2 a.m. before declining to a moderate (G2) storm before dawn. Based on past aurora behavior and the latest forecast, peak activity will likely be from about 11 p.m. to 1 a.m. local time.

Sun and sunspots
A flare that occurred in sunspot group 3076 on August 14 hurled a plume of blazing hydrogen gas called a filament into space. That material is now approaching Earth and will likely spark auroras Wednesday night. Group 3078 has also been flaring a lot recently, possibly setting the stage for future auroras.
Contributed / NASA, SDO

More good news! The shock from the impact will be significant, with storming continuing at the moderate level through Thursday night, Aug. 18. Two nights in a row of aurora — can we be so lucky? Let's hope so!


Always there are caveats. Sometimes the best forecast storms blow by without even touching us. Or they arrive early during the daytime. You drive 100 miles, stay up late and see nothing. I try to remind myself that nature always has the upper hand and can be as predictable as capricious. Think of the aurora as more like a relationship, where compromise (clouds, failure to appear) helps us take things in stride. That said, I'm reasonably confident we'll have a wonderful show.

Watching the northern lights requires no special equipment, just your eyes and if you like, a chair. The only essentials are a dark sky to the north with as little city light pollution as possible and clear weather. Partly cloudy works, too.

Aurora with clouds
Clear skies are best, but you can still see the northern lights through clouds as long as they're not too thick. Green streaks are firefly flashes.
Contributed / Bob King

My local forecast isn't looking great. We expect mostly cloudy skies with maybe some clearing around midnight. Like you, I listen to the National Weather Service forecast, but my favorite tool is Clear Sky Chart , which displays an hourly cloud forecast. Each hour is shown as a small, colored square. The darker blue the square, the clearer the sky. A white one indicates overcast.

If you click on a square, a map showing your location and the predicted cloud cover pops up. Go to the website, then click the Find a Chart link to the left, fill in your location, and you're ready to go. I like to check it several times a day for the latest prediction. If things look dire for your town, click the Within 180 miles link to check on other locations that may offer better weather prospects.

Mars moon August 18 2022.jpg
The moon, Mars and the Pleiades will gather in the eastern sky during the wee hours of Thursday, August 18.
Contributed / Stellarium

We always like to know what the moon's doing since its glare can compromise a delicacy like the aurora. Good news on that front, too. It rises Weds. night around 11 p.m. local time near last quarter phase and shouldn't pose much of a problem. In fact, it presents yet another scenic opportunity for skywatchers — if you're out late, the moon triples up with Mars the Pleiades star cluster. Keep an eye out for this pretty trio.

I hope you have clear skies. Much luck to you! I'll update the aurora's progress Wednesday night on my Facebook page.

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at nightsky55@gmail.com.
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