Flickering Aurora

One of the stranger kinds of aurora is one rarely recognized by eye. Called flickering aurora by the University of Alaska researchers who first described it, this aurora undergoes rapid change somewhat akin to that seen when a candle's flame is struck by a sudden draft of air.

After more than a year of recording flickering auroras on sensitive television systems used to observe the night sky, the flickering aurora was finally recognized as being something other than a problem with the TV sets. The crucial observation came one night in 1966 when such an intense display of flickering aurora occurred that it was easily seen by the unaided eye as well as the sensitive TV systems.

Flickering occurs only near the time of the auroral breakup, this is the time when quiet auroral arcs rapidly grow brighter and twist into contorted shapes that sweep across the sky. Why flickering occurs only at this time and why it occurs at all are unknown.

Curiously, in each display flickering aurora oscillates at a rather fixed frequency between 7 and 13 cycles per second. This is just the frequency range of alpha waves in the human brain.

Alpha waves become dominant when a person changes from an active thinking state to a passive, blank state. Apparently persons prone to epilepsy can sometimes be caused to undergo petit and grand mal seizures when exposed to light flashing near 10 cycles per second, the frequency of flickering aurora. It is also been suggested that some auto and aircraft accidents have been caused by persons being lulled into a blank alpha-dominant state by rapidly flashing lights. So far, the flickering aurora has not been blamed for accidents or epileptic seizures, but who knows?