After a bright northern lights display the night sky sometimes is filled with pulsating patches of light.
This pulsating aurora is fairly weak compared to normal aurora, so you need to be at a very dark place to see it. It also helps if you let your eyes get used to the darkness of the night for at least ten minutes.
The same patches of aurora then appear and fade out again constantly over the whole sky, a pulsating process that might go on for hours.
Usually the period of pulsating is approximately half a minute but very rapid flashes of less than a second are also observed.
Pulsating aurora takes place in the upper part of the atmosphere that is called the ionosphere, at heights between 150 and 400 kilometers.
The exact mechanism that causes pulsating aurora is still a mystery.
The timelapse footage was shot with a modified Nikon D1H digital still camera at one frame per second and a three step noise reduction was applied in post production.
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