The solar wind constantly streams toward theEarth, but dont worry because a protective magneticfields surrounds our planet. The same magnetic field that makes your compasspoint north also steers the particles from the Sun to the north and southpoles. The charged particles become trapped in magnetic belts around the Earth.When a large blast of solar wind crashes into the Earths magnetic field first gets squeezed and then the magnetic fieldlines break and reconnect.
The breaking and reconnecting of the magneticfield lines can cause atomic particles called electrons trapped in the belts tofall into the Earths atmosphere at the poles. As theelectrons fall into the Earth, they collide with gas molecules in theatmosphere, creating flashes of light in the sky.
Each atmospheric gas glows a different color.Oxygen and nitrogen glows red and green and nitrogen glows violet-purple. Asthese various colors glow and dance in the night sky, they create the NorthernLights and the Southern Lights.
Watching auroras(北极光)is fun and exciting, but normally you can only see them in places far northlike Alaska and Canada. The movement of the aurora across the sky is usuallyslow enough to easily follow with your eyes but they can also pulsate(跳动), flicker(闪烁), or even move like waves.During solar maximum, 5 auroras are seen as far south as Florida, even Mexico!Aurorasoften seem to be very close to the ground, but the lowest aurora is still about100 kilometers above the ground, a distance much higher than clouds are formedor airplanes can fly. A typical aurora band can be thousands of kilometerslong, a few hundred kilometers high, but only a few hundred meters thick.
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