The sun is stormy and has it own kind of weather. It is so hot and active that even the Sun’s gravity cannot hold its atmosphere in check! Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour. These particles are called plasma, and the stream of plasma coming from the Sun is called the solar wind. The more active the Sun, the stronger the solar wind.
The solar wind constantly streams toward the Earth, but don’t worry because a protective magnetic fields surrounds our planet. The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles. The charged particles become trapped in magnetic belts around the Earth. When a large blast of solar wind crashes into the Earth’s magnetic field first gets squeezed and then the magnetic field lines break and reconnect.
The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into the Earth’s atmosphere at the poles. As the electrons fall into the Earth, they collide with gas molecules in the atmosphere, 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. As these various colors glow and dance in the night sky, they create the Northern Lights and the Southern Lights.
Watching auroras is fun and exciting, but normally you can only see them in places far north like Alaska and Canada. The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate, flicker, or even move like waves. During solar maximum, auroras are seen as far south as Florida, even Mexico!
Auroras often seem to be very close to the ground, but the lowest aurora is still about 100 kilometers above the ground, a distance much higher than clouds are formed or airplanes can fly. A typical aurora band can be thousands of kilometers long, a few hundred kilometers high, but only a few hundred meters thick.
We hope you are able to travel to far-north places like the Arctic Circle and see the Northern Lights at least once during your lifetime. We know you will never forget it!
1.The Sun’s gravity is too weak to keep its plasma from flowing to the Earth.
A. right B. wrong C. not mentioned
2.The Earth is quite safe with a magnetic field surrounding it to protect it from the attack by the solar wind.
A. right B. wrong C. not mentioned
3.Some scientists are worrying about the possible disappearance of the Earth’s protective magnetic field in the future.
A. right B. wrong C. not mentioned
4.The auroras are formed when the electrons falling into the Earth’s atmosphere at the poles and colliding with gas molecules in the atmosphere.
A. right B. wrong C. not mentioned
5.You cannot see the Northern Lights unless you are in Alaska or Canada.
A. right B. wrong C. not mentioned
6.Tens of thousands of tourists take special trips to Norway and Sweden every year to watch the Northern Lights.
A. right B. wrong C. not mentioned
7.An aurora is generally close to the ground and is very long and thick.
A. right B. wrong C. not mentioned
答案与解析：
1.分析文章标题：The Northern Lights(北极光)
2.直接解题：
1. The Sun’s gravity(引力) is too (太...而不能...)weak(弱的， 虚弱的) to keep its plasma(等离子体) from (阻止/防止...)flowing(流动) to the Earth.
A. right B. wrong C. not mentioned
1.B. 细节题。 利用问题句中的特征词(the Sun’s gravity, the Earth )及细节信息词(plasma) 共同作为答案线索， 在文章中查找答案相关句：
(第一段)The sun is stormy(狂暴的，多暴风的) and has it own(自己的) kind of weather(气候，天气). It is so(如此...以至于...) hot(热的， 辣的) and active(活跃的) that even(甚至) the Sun’s gravity (引力)cannot hold (控制)its atmosphere(大体层， 气氛) in check! Energy(能量) flows away from (从...流出)the Sun toward(向) the Earth in a stream of (以一连串的形式)electrified(带电的) particles(粒子) that move at speeds (以...的速度)around a million miles per(每) hour(小时). These particles(粒子) are called(被称为) plasma, and the stream(流，溪， 一连串) of plasma coming from(来自) the Sun is called the solar wind(太阳风). The more active the Sun, the stronger the solar wind.
责任编辑：虫虫
