NORTHERN LIGHTS

Increase Your Chances Of Seeing This Most Spectacular Of Northern Spectacles

By Bob King

Northern lights happen when a solar storm called a flare or a gash in the sun’s atmosphere called a coronal hole sends high speed streams of tiny, subatomic particles in great, ghostly waves toward the Earth. Normally, Earth’s magnetic defenses shed those particles and we’re no worse for the wear, but occasionally they link into our magnetic field and make a beeline for the atmosphere.

When the torrent collides with oxygen and nitrogen atoms and molecules about 60-200 miles overhead, they get excited. Excited atoms “relax” by releasing energy as light. That’s exactly what happens in the aurora. Both oxygen and nitrogen shoot off tiny jolts of red and green light. Taken together, they create the amazing colors and shapes of the aurora.

Galileo himself gave us the name aurora borealis back in 1619. Aurora is the Roman goddess of dawn, and “borealis” is a Greek word that refers to the “north” or “north wind.” If you’ve ever seen the aurora, it often begins as a glow above the northern horizon that resembles dawn. There’s also an aurora australis or southern lights that appears at the same time as the northern version.

The best time to see them is within a day or two of a large flare, a massive explosion in the sun’s lower atmosphere with the power of millions of nuclear bombs. Flares often arise in large sunspot groups. But since we’re now near the low end of the 11-year solar cycle, there aren’t very many big sunspots. That’s why the aurora is less frequent now than a few years ago. Still, it can occur anytime.

Auroras are most common in the Arctic and Antarctic regions but during strong activity, can work their way south to the northern U.S. Northern Minnesota is an excellent place to see at least a half dozen shows a year. You can check my Astro Bob blog (astrobob.areavoices.com) and Spaceweather (spaceweather.com) for alerts about upcoming storms and potential auroras.

Or you can check the Planetary Kp index at swpc.noaa.gov/products/ planetary-k-index. Kp is an indicator of magnetic activity high in the atmosphere. It’s rated from 0 to 9, with “0” meaning no chance for an aurora to “9” for a raging, sky-filling storm of light. If the Kp is “3” or less, it shows up as a green bar at the site. Kp=4 is yellow, and 5 and above are red. Want to know if an aurora’s likely to show? If you see red bars reaching to 5 or higher on the right side of the graph, it’s time to head outside for a look! That simple.

To photograph the aurora, you’ll need a camera, tripod and preferably a wide-angle lens, though a “normal” lens will work OK, too. Your camera must be able to take time exposures of at least 15 seconds.

First, use the camera’s auto-focus feature to focus on a distant object like the moon or a cloud, then click your lens into “M” or manual mode.

You’re now set for the night. If there’s no moon out, secure the camera to the tripod, set the lens to M and focus on a bright star using the camera’s “live view” function. You’re now ready to take pictures of the aurora.

Set the ISO to 800 or 1600, the lens to its widest setting (usually f/2.8, 3.5 or 4.5) and expose from 10-30 seconds. Check the camera’s back viewing screen to make sure your exposures are in the ballpark.

I do a lot of aurora watching from dirt roads in the countryside north of the city of Duluth. Your best bet is to drive north of town since most northern light displays happen in the northern sky. Good places to look are up Rice Lake Road in the Island Lake area, Pequaywan Lake Road and the Fish Lake area. You can also drive up the North Shore to a pull-out and watch from there.

Seeing a great aurora display takes time, patience and a willingness to sacrifice sleep. Sometimes the lights will start out looking unimpressive, but don’t let them fool you. Often, if you stick around, you’ll see an amazing show. Make a habit of looking up at night, and I promise you that sooner rather than later, you’ll have your fill of one of nature’s grandest spectacles.

Bob King is the Duluth News Tribune’s photo editor and an amateur astronomer.

Book Signings

Bob King will be signing copies of his new book, “Wonders of the Night Sky You Must See Before You Die,” at the following events.

Thursday, April 26

1-3:30 p.m. Duluth News Tribune

Sunday, April 29

1-3 p.m. Bookstore at Fitger’s

Saturday, May 5

2:30-4 p.m. Zenith Bookstore

Wednesday, May 9

6-7 p.m. Marshall W. Alworth Planetarium at UMD followed by a free sky show