PRIEST LAKE / NORTHERN LIGHTS

By John D Sahr Photo courtesy of Elkins Resort



Many of us have seen the Northern Lights at Priest Lake.

The Northern Lights happen when high speed electrons crash into atoms and molecules in the Earth's upper atmosphere, at altitudes above about 95 km (60 miles). The atoms and molecules that got crashed into eventually settle down, and in the process they emit a little bit of light of a particular color. The color depends upon the atom or molecule that was struck. The usual colors that we see are white, green, and (occasionally) red. In other words, the Northern Lights are pretty similar to neon signs, but oxygen and nitrogen are the important gases.

The Northern Lights appear white when they are not very bright; the black-and-white receptors of our eyes present them as "white" even though they are actually green. When you see the Lights as bright green, perhaps looking like curtains, that is a special treat. The reason that they look like curtains is that electrons can flow very easily up and down along the magnetic field lines of the Earth, but not very easily across the magnetic field lines. When you see the "curtain" shaped aurora, you are, quite literally, seeing a trace of the Earth's magnetic field.

At the latitude of Priest Lake, we almost always see the Northern Lights to the north, where (from our point of view) the magnetic field lines are pretty much vertical. Read more...