The northern lights flame in pale green, red or white and shimmer across the sky, and we are filled with a sense of beauty, wonder and awe. I wish everyone had the chance to see the swirling and pulsating displays, but it takes a dark sky, far from the city lights and pollution.
The northern lights, also called the aurora borealis, are visual evidence of disruptions to the earth's magnetic field. What we know is that the aurora is caused by high energy-charged particles, electrons and protons streaming from the sun at speeds up to 3 million miles per hour. The flow of charged particles is known as the solar winds. Solar wind gusts, captured and concentrated by the earth's magnetic field near the poles, can interact with gases high up in our planet's atmosphere, causing them to glow like gases in a fluorescent light bulb.
The fact that the northern lights do not show themselves on most nights here in Minnesota makes them all the more impressive. The best times of the year to see them are March and April or September and October, when the earth's magnetic field is most closely aligned with the sun's. The best hour is just before midnight, especially when the moon is new and the skies darker. The finest displays seem to light up the whole sky, but even then they seldom exceed the light of the moon during its quarter phase. Northern lights are visible about 200 nights a year at the latitude of Fairbanks, Alaska. East-central Minnesota can expect the natural light show about 30 times a year.
Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.