Dear Tom,
Is it possible to see the northern lights in Chicago?
Tom Hallerson, Chicago

Dear Tom,
We can indeed see the aurora borealis, also known as the northern lights, in Chicago, but not very often. Aurorae are visible in Chicago about once every two years, but the sightings are limited by the nighttime glow of city lights. Far from the city, say west of the Fox Valley, aurorae can be spotted more frequently, perhaps three or four times a year. The sun is constantly ejecting charged particles from its upper atmosphere (the corona), creating the solar wind. When that wind strikes the upper atmosphere of the Earth, the ionosphere, aurorae are created. The Earth’s magnetic field deflects the charged particles toward the North and South Polar regions, causing the ionosphere to fluoresce.