Recently I was waiting on the shores of a lake in Northern Minnesota with my parabolic microphone in my hand and my digital audio recorder ready to record. It was one o’clock in the morning and I was waiting for the resident loons on the lake to begin their nightly serenade. I was there to record the four distinct vocalizations of the Common Loon but what I got was a streaming curtain of light across the northern sky-the aurora.
The name aurora comes from the Roman Goddess of the dawn and is the name given to the spectacle of light that appears in the skies of earth near the polar regions. In the northern hemisphere, they are called aurora borealis or northern lights. In the southern hemisphere they are called aurora australis or the southern lights.
The auroras are caused by the sun. Sometimes the sun has violent storms and spews out a stream of charged particles (plasma) in an event called a coronal mass ejection. The results of the storms are solar winds traveling at speeds of 1 to 2 million miles per hour and are filled with tiny highly charged particles.
It takes two or three days but eventually the solar wind reaches the earth. When the particles do arrive, they are deflected towards the North and South poles by the earth’s magnetic field. The particles hit and interact with our atmosphere and the sky begins to glow.
The delicate colors of the auroras depend on the height at which the energy particles collide with our atmosphere. Street lamps and neon signs emit different colors of light depending upon the types of gas trapped within the fixture. The same applies for the auroras. If the predominant gas is oxygen and nitrogen the auroras will be red. This is rare and only occurs at times of maximum solar activity. The most common color is green, and yellow again caused by oxygen, but at lower levels.
The auroras occur on 27 day intervals and usually last for several nights in a row. Northern lights that occur just after dark are not very showy. The best displays occur around midnight or shortly after. The auroras are never absent from the earth. Every hour of the day, every day of the year, the auroras are blazing somewhere on the earth. However most people can go many years between seeing the northern display. The reason is the aurora spends most of its time around the ends of the earth, where there are plenty of penguins and polar bears but few humans.
The best place to view the aurora lights lie within an auroral zone that encompasses the northern polar regions. From Alaska through the Northwest Territories of Canada, around to Norway, Russia and back to Alaska. Along this band, the lights can be seen on virtually every cloudless night from autumn to spring. Small expansions of the auroral zone are common and aurora often spills out to neighboring regions such as our.
Oh and by the way, the loons never called that night. I think they were speechless, as I was, and just watched the light show unfold over they heads.
Until next time…