Dear Tom,
While camping in the “north woods” (300 miles north of Winnipeg, Canada), we saw the aurora borealis. How high up do auroras form?
— John Lutz
Dear John,
Dr. Fredrik Carl Stormer (1874-1957), a professor of mathematics at the Institute of Theoretical Astrophysics in Blindern, Norway, pioneered the use of photography to study auroras in the early 1900s. He and his research team simultaneously photographed auroras from many different locations and, by means of triangulation and geometry, calculated the height in the atmosphere at which they occur.
Stormer found that auroras occur in two separate “zones of activity” — a lower zone about 50 to 200 miles above the Earth’s surface and an upper zone 350 to 630 miles aloft.
Stormer also found that most auroras originate in the lower zone.
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