One of the great things about being at or near the Earth’s polar region is the opportunity to witness the incredible celestial display known as the Northern Lights (aurora borealis) in the Arctic or the Southern Lights (aurora australis) in the Antarctic. I remember first seeing the aurora borealis as a doctor at the U.S. Navy’s 1990 Applied Physics Laboratory Ice Station on the Arctic ice cap. Shimmering bands of green light dancing across the ink black night sky; it was truly awe inspiring.
So it was with great anticipation I awaited my first glimpse of the aurora australis soon after the Sun bid farewell in March. It was on a clear night during nautical twilight that I was rewarded with an impressive upper atmospheric light show. I stayed outside to watch it for as long as I could withstand the cold.
The aurora results from the collision between energetic charged particles and atoms in the upper atmosphere. The two-million degree heat of the Sun’s corona produces a solar wind composed of electrons and ionized atoms. With during periods of increased solar activity and sun spots, coronal mass ejections increase the intensity of the solar wind. The Earth’s magnetic field traps these particles and accelerates them towards the poles along the lines of magnetic force. The solar wind particles then collide with atoms of oxygen and nitrogen in the upper atmosphere (50 miles or 80 kilometers), exciting or energizing the atoms. When the atoms return to their normal state, they give off light…usually green for oxygen atoms and blue or red for nitrogen atoms. The interactions are more complex than I have described, but this is the basic idea.
Despite to extreme cold and darkness here at the South Pole, I try to get outside as often as I can in hopes of enjoying as many auroral displays possible. Fortunately, this is a time of increased solar activity, so hopefully this will be a good season for the Southern Lights. I will try to capture some good images of the aurora to share with you in the remaining months of darkness at the South Pole. One of the scientists wintering here, Robert Schwarz, is an expert at capturing aurora and has kindly provided advice to the newcomers, as well as sharing photographs from previous years.