Astro Bob: Auroras bloom like flowers — a look back and tips for what's ahead
With solar activity continuing to increase, auroras are becoming more frequent. Here's an alert app you don't want to be without.
I hope you caught the surprise northern lights show on May 19-20. Space weather experts did not expect the storm, but a release of material from the sun called a coronal mass ejection dealt the Earth a glancing blow that night. It was enough to break through our magnetic defenses and spark a wonderful light show.
Unlike the bigger storms in April and May this one mostly held to the northern sky. There were lots of colors and forms — pillars, arcs, pleated curtains and tall, faint rays reaching to the Big Dipper near the zenith.
Like college revelers, the subatomic party carried on into the night, still tossing out rays well after 2 a.m. At times, the display faded back only to return in another form. That's why it's so hard to tear yourself away from an aurora. You may have seen a dozen or more displays, but variations are endless and captivating.
For instance, I saw all the familiar forms pictured in the photos, but my friend Will in northern Wisconsin noticed a very faint red arc crossing from east to west nearly overhead around 10:45 p.m. CDT. While I did make a few sweeps of the entire sky with my eyeballs I totally missed that one. Did you see it? I suspect it was a stable auroral arc caused by heating of the Van Allen radiation belts during auroral storms.
Nearly all auroras originate from what goes on on the sun. Solar blasts called flares, along with holes in the sun's corona and random ejections of plasma in our direction send hordes of electrons and protons (the stuff of the sun) in our direction. They find their way into the upper atmosphere traveling at some 44 million miles an hour and excite oxygen and nitrogen atoms to produce ghostly streaks and arcs of red, blue, purple and green.
The past 18 months the sun has been on a tear with multiple sunspot groups dotting the glaring disk nearly every day. Some have been large enough to make out with the naked eye using a safe solar filter. Magnetic energy concentrated in these darker, cooler regions gives rise to flares and other activity that can lead to spectacular light shows in Earth's skies.
On Sunday, May 21, for example, there were eight sunspot groups visible through a small, properly filtered telescope. One of them, Region 3311, has a complex, unstable magnetic field ideal for producing flares. On May 20, I set up a special telescope for viewing flares and found one already underway! The group's continued rumblings may lead to more auroras in the next two weeks.
The most recent forecast shows a fair chance for a minor to moderate storm arriving on Tuesday night, May 23, due to the combined influence of a coronal mass ejection and high speed solar wind from one of those coronal holes. It's still early but you may want to remain vigilant that evening. There's also a possibility for aurora on Sunday night, May 21. Check my Facebook page for updates.
Recently, I found a very useful (and free) iPhone aurora app called Aurora Forecast & Alerts by LW Brands LLC (try My Aurora Forecast & Alerts for Android phones). It get my highest rating because it pesters me with vibration alerts more often than any other aurora app I've ever used. I'm not complaining! The app also has data and diagrams, but the alert feature is its most useful function.
Of course, no one will be seeing any auroras until the wildfire smoke dissipates. By good fortune it drifted out of the northern Wisconsin-Minnesota region on May 19 in the nick of time and left the cleanest sky I've seen in nearly a week. The next day it returned with a vengeance. To keep track of where the smoke is I turn to NOAA's Fire and Smoke map . You'll also find a comprehensive written forecast at Satellite Smoke Text Product . Check it from time to time to see what the trend is. Don't worry if you arrive to find a blank map. Sometimes it takes the agency a little time to update it.
The yellow and red suns we see are from wildfire smoke drifting south and east from massive fires in northeastern British Columbia, central and northern Alberta, central and northern Saskatchewan, and the southern part of the Northwest Territories.
High temperatures and a dry spring are behind the blazes. Smoke both absorbs light, dimming the sun, and scatters away all the cooler colors, leaving only yellow, orange and red. Contrary to popular belief forest fires don't necessarily produce spectacular sunsets. They're drained of color if you ask me. But they make for a spectacular red sun!