Scientists have found the elusive trigger that sets off the most striking visual outbursts, known as pulsating aurorae or blinking lights around Earth's polar regions. (See aurorae pictures.)

Though typical auroras usually stretch more than 620 miles (a thousand kilometers), and last only minutes at a time, pulsating aurora are small glowing patches of light about a 62 miles (a hundred kilometers) wide that flash on and off every 5 to 40 seconds. This flickering gives the appearance of exploding lights in the sky.

"The driver behind auroral pulsation has been a long-standing question in the auroral physics community for more than four decades," said project leader Toshi Nishimura, a researcher at