The Auroral Oval – What is it?

Hang onto your hats people, we’re going to get a little scientific for a minute in an effort to take a closer look at one of our favorite sky events, the Aurora Borealis.

We’re all more than likely familiar with the Aurora. We’ve seen countless images while craving an opportunity to make some of our own while witnessing the spectacular event. We’ve discussed briefly, in a previous post, the Aurora, and our trips to Fairbanks each year in a quest for stunning images of this awe inspiring event.

Backcountry Journeys visits the sub-arctic regions of Alaska several times per year in search of the Aurora Borealis. Ultimate Northern Lights is an amazingly unique trip and typically produces incredible results for our photographers. So, we thought it would be worthwhile to take a closer look into the aurora because it’s cool, and why not?

When we look up and see the Northern Lights, we are only seeing a tiny section of a huge auroral oval. The geomagnetic field surrounds the Earth and extends into space as the magnetosphere, and the Geomagnetic Pole is the center of the region around which the Northern Lights can be seen.

At the center of our solar system lies the sun, the yellow star that sustains life on our planet. The sun’s many magnetic fields distort and twist as our parent star rotates on its axis. When these fields become knotted together, they burst and create sunspots. Usually, these sunspots occur in pairs; the largest can be several times the size of Earth’s diameter.

At the center of the sun, the temperature is 27 million degrees Fahrenheit. As the temperature on its surface rises and falls, the sun boils and bubbles. Particles escape from the star from the sunspot regions on the surface, hurtling particles of plasma, known as solar wind, into space.

It takes these winds around 40 hours to reach Earth, and when they do they cause the famous and dramatic displays that attract so many visitors, like us, to the locales where the lights can be seen. The colors most often associated with the aurora are pink, green, yellow, blue, violet, and occasionally orange and white. Typically, when the particles collide with oxygen, yellow and green are produced. Interactions with nitrogen produce red, violet, and occasionally blue colors.

The type of collision also makes a difference to the colors that appear in the sky: atomic nitrogen causes blue displays, while molecular nitrogen results in purple. The colors are also affected by altitude. The green lights typically in areas appear up to 150 miles high, red above 150 miles; blue usually appears at up to 60 miles; and purple and violet above 60 miles.

These lights may manifest as a static band of light, or, when the solar flares are particularly strong, as a dancing curtain of ever-changing color.

The auroral oval is the footprint in the atmosphere of the boundary between the highly stretched field lines of the polar cap and the more normal field lines at lower latitudes. When the solar wind blows hard, this boundary moves equatorward – sometimes as far as Huntsville, Tel Aviv, or Kyoto – as more high latitude field lines are blown out into the tail.

Suppose we could wait for when Huntsville or Kyoto light up and go there. Instead, we travel to Fairbanks for the Lights because the town boasts the clearest night skies in Alaska and it’s prime location directly underneath the Auroral Oval make it second to none as a destination for photographing the Northern Lights. Oh, and when in Fairbanks we get to dine at Lavelle’s. Shameless plug here, we know.

We time these excursions so that we are there during the best months of the year for the Aurora – spring & fall are often best with winter as a close second. In Alaska’s long summer days it doesn’t get dark enough to witness the phenomenon.

The result of all this amazing science is a light show unrivaled by any other sky event. We hope that you can join us on Ultimate Northern Lights and see for yourself this marvel unravel in front of your own eyes!