Göran Strand from Östersund, Sweden captured this time-lapse video showing what happened on March 17, 2013 when a coronal mass ejection (CME) from the sun hit Earth’s magnetic field. It starts slowly … but then becomes very beautiful as auroras ripple across the sky. The entire 3-minute video actually took place over about 4 hours.
What causes an aurora? The March 17 aurora originated from sunspot AR1692, which erupted on March 15, 2013 at about 0600 UTC. This explosion on the sun took hours to unfold, and produced an M1-class solar flare and a bright coronal mass ejection, or CME. The CME consists of charged solar particles hurtling across space. As often happens, the March 15 CME was aimed so that Earth was in the path of the particle stream.
When the charged solar particles struck Earth’s magnetic field, a geomagnetic storm resulted. In other words, when the charged particles from the sun struck atoms and molecules in Earth’s atmosphere, they excited those atoms, causing them to light up.
What does it mean for an atom to be excited? Atoms consist of a central nucleus and a surrounding cloud of electrons encircling the nucleus in an orbit. When charged particles from the sun strike atoms in Earth’s atmosphere, electrons move to higher-energy orbits, further away from the nucleus. Then when an electron moves back to a lower-energy orbit, it releases a particle of light or photon.
What happens in an aurora is similar to what happens in the neon lights we see on many business signs. Electricity is used to excite the atoms in the neon gas within the glass tubes of a neon sign. That’s why these signs give off their brilliant colors. The aurora works on the same principle – but at a far more vast scale.
Bottom line: Beautiful video by Göran Strand in Sweden of auroras seen on March 17, 2013.
Deborah Byrd created the EarthSky radio series in 1991 and EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.