I’m sure everyone has their aurora stories from May 10th and 11th. Whether you saw it for yourself or not, there was a flood of photos online. People as far south as Florida saw the aurora due to a massive sunspot/coronal mass ejection/geomagnetic storm. Yes, I’m throwing word salad, but they are all correct and in the correct order, but I might not be able to properly explain it all even though that is part of my job.
Summer tours are all about wildlife and totem parks for me these days. In winter I facilitate people’s northern lights adventure. Whether I’m driving them to and from Borealis Basecamp or guiding a week-long, small group tour, seeing the aurora is always the goal. Let me share with you what I tell all of my guests about what they hope to see.
I always start the aurora speech by saying that you need three things to see the northern lights. First, you need a dark sky. That’s why there’s an aurora season up in Fairbanks from late August to early April. Nobody up there was able to see this last one because it wasn’t dark enough. Second, you need a clear sky. The aurora happens anywhere from 50,000 to 200,000 feet up, but the clouds are much closer to earth. Cloudy skies are like Mother Nature pulled the curtains closed on the show. Third, the sun has to be active enough to make the show happen in the first place. That’s what happened two weeks ago.
If you want to see the northern lights you can look at aurora forecast apps or websites like spaceweatherlive.com Or you can type aurora forecast into your favorite search engine. UAF has a really good forecast page and hosts a skycam located north of Fairbanks that can allow you to watch the entire night sky from anywhere.
The sun is more than a bright, shiny thing in the sky. It has its own weather and a very tangled magnetic field. I barely understand what goes on to cause sunspots and coronal loops, but I do know that sometimes those loops will twist until they burst and fling plasma, or energized particles out into space, creating the solar wind. My favorite analogy is to compare the sun to a pan of tomato sauce simmering on the stove. If the heat is up, it will splatter in all directions, leaving a red ring on the stove top. If you leave something near the pan, it will get splattered with the sauce. This is what the sun does, only in all dimensions. If a “splatter” hits earth, we have an aurora event.
The charged particles on the solar wind could be damaging to us if they were to all hit earth, so it is good that we have our magnetic field to act as a shield. Most of the particles will be deflected and continue on through space. Some will follow the magnetic field lines down into our polar regions, forming an auroral ring. That is where they encounter the gas atoms and molecules in our atmosphere and interact to cause that glow.
In the upper atmosphere, charged particles will hit gas atoms, most often oxygen, and transfer energy to the gas atoms. This pushes the atoms to a higher energy level where they become unstable and want to shed the extra energy as soon as possible. They do this in the form of photons, also called light particles. If there are enough photons you will see the lights.
The aurora guides I work with tell me that the Kp index is not the best indicator for a later show, but it is easy to understand so I like to start there.
The Kp index goes from 0 to 9. 0 is exactly what it sounds like. Nothing is hitting our atmosphere and there will be no lights. 1 or 2 on the Kp index is very faint. It might look like a mist or fog, but glows green when you take a picture with your camera on night settings.
A Kp of 3 to 4 is much more visible. In fact, this is usually a pretty good show. It typically shows up as a green ribbon across the sky, sometimes splitting into a curtain of light or spreading across the sky. With more energy, there can be more color. Different energy levels can cause photons of different wavelengths, making different colors. Most often, that appears as layers of magenta and white in a curtain of green.
At a Kp of 5, 6 or higher, the aurora will often dance. At 7 or 8 other colors are more likely to appear. With more energy hitting the atmosphere, charged particles can plunge deeper and nitrogen molecules can get in on the show. Where oxygen glows green, white, and magenta, nitrogen will glow red, blue, and deep purple. It makes for a very colorful show.
May 10th was a very bright, energetic aurora. It hit higher on the Kp index than anything we have seen in years, as shown in the screenshots at the beginning. Amazingly, the sky was clear and dark enough that I was able to get some beautiful photographs. I hope you enjoy them.
If you want a chance to see the aurora for yourself, come up to Fairbanks for a week in winter. Be prepared to miss out on sleep. Plan to check out some of the museums and spend time out in the snow. You might not want to live there, but I’m sure you will see why some of us don’t want to leave.
