For those of us who haven’t had the good fortune (yet) of seeing the Northern Lights perhaps they always seem a bit strange and otherworldly, but this video below really seems to turn that up a notch.
The great speed of movement and diversity of colors seen in the video is, I’m told, the result of pronounced solar activity, and is relatively rare. So enjoy. When watching the video, though, I suggest keeping the sound off, the guy talks quite a lot. 🙂
Some background on aurorae for those that are curious:
“An aurora (plural: aurorae or auroras; from the Latin word aurora, “sunrise” or the Roman goddess of dawn) is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). The charged particles originate in the magnetosphere and solar wind and, on Earth, are directed by the Earth’s magnetic field into the atmosphere. Most aurorae occur in a band known as the auroral zone, which is typically 3° to 6° in latitudinal extent and at all local times or longitudes. The auroral zone is typically 10° to 20° from the magnetic pole defined by the axis of the Earth’s magnetic dipole. During a geomagnetic storm, the auroral zone expands to lower latitudes.”
“The aurora borealis most often occurs near the equinoxes. The northern lights have had a number of names throughout history. The Cree call this phenomenon the ‘Dance of the Spirits’. In Medieval Europe, the auroras were commonly believed to be a sign from God.”
“In the traditions of Aboriginal Australians, the Aurora Australis is commonly associated with fire. For example, the Gunditjmara people of western Victoria called aurorae ‘Puae buae‘, meaning ‘ashes’, while the Gunai people of eastern Victoria perceived aurorae as bushfires in the spirit world. Similarly, the Ngarrindjeri people of South Australia referred to aurorae seen over Kangaroo Island as the campfires of spirits in the ‘Land of the Dead’. Aboriginal people in southwest Queensland believed the aurorae to be the fires of the ‘Oola Pikka‘, ghostly spirits who spoke to the people through aurorae.”
Red: At the highest altitudes, excited atomic oxygen emits at 630.0 nm (red); low concentration of atoms and lower sensitivity of eyes at this wavelength make this color visible only under some circumstances with more intense solar activity. The low amount of oxygen atoms and their very gradually diminishing concentration is responsible for the faint, gradual appearance of the top parts of the “curtains”.
Green: At lower altitudes the more frequent collisions suppress this mode and the 557.7 nm emission (green) dominates; fairly high concentration of atomic oxygen and higher eye sensitivity in green make green auroras the most common. The excited molecular nitrogen (atomic nitrogen being rare due to high stability of the N2 molecule) plays its role here as well, as it can transfer energy by collision to an oxygen atom, which then radiates it away at the green wavelength. (Red and green can also mix together to pink or yellow hues.) The rapid decrease of concentration of atomic oxygen below about 100 km is responsible for the abrupt-looking end of the bottom parts of the curtains.
Yellow and pink: A mix of red and green.
Blue: At yet lower altitudes atomic oxygen is not common anymore, and ionized molecular nitrogen takes over in visible light emission; it radiates at a large number of wavelengths in both red and blue parts of the spectrum, with 428 nm (blue) being dominant. Blue and purple emissions, typically at the bottoms of the “curtains”, show up at the highest levels of solar activity.
Image Credit: NASA/J Curtis of U Alaska/ACRC