Soon curved bands of light appear above the glow, and beams begin to shoot upward toward the middle of the sky. The beams keep changing their positions and their brilliance from second to second. At its full intensity, the aurora covers the entire sky with shifting curtains of light like draperies waving in the wind. These lights seldom occur less than 50 miles above the earth, and are sometimes as much as 60 miles high. The light display of the aurora is greatest at times of magnetic storms.
Displays are most frequent around the time of greatest sunspot activity.