By combining simultaneous observations by NASA s aurora-watching Polar satellite and Japan s Geotail satellite, scientists have learned that the best auroral light shows happen when a solar flare lets loose a magnetic vortex, or bubble, of plasma that slams into the Earth s magnetic field. These collisions cause the Earth s magnetic field to shrink on the daylight side of the planet and stretch out like a comet s tail on the nighttime side of the planet. If the Earth s magnetic tail stretches long enough, parts of it can break free as separate magnetic bubbles, which continue moving off into space on the solar wind. Breaking free of Earth s magnetic field is a violent event, however, like breaking a colossal rubber band. It causes a massive amount of energy to fly back toward Earth s poles on the nighttime side of the planet, making nighttime auroras much brighter and bigger than those on the daylight side of the planet.
Auroras appear simultaneously in the atmosphere above the North and South poles.
Glowing blue, violet, red, yellow and green, the auroral lights in some ways represent subatomic skid marks. Each of the colors corresponds to a specific wavelength of light emitted when electrons associated with atmospheric gases slow down. As the electrons drop back to their normal energy state, they release a burst of light that becomes the aurora. The bigger the quantum leap, the higher the energy and the bluer the color. Smaller quantum leaps produce red and green auroras.