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Questions 46-50
Auroras, often called Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis), are
spectacular light displays (from the Latin word aurora, “sunrise” or the Roman goddess of dawn)
predominantly seen in the high latitude (Arctic and Antarctic) regions. Auroras occur because of
interactions between Earth’s magnetic field and solar winds. The solar wind is a stream of charged
particles emitted from the sun’s corona that travels far into space at speeds of up to 400 miles per second.
Charged particles within the solar winds collide with atmospheric atoms and molecules when they reach
Earth’s magnetic field. The collisions cause quantum leaps, which mean the kinetic energy within the
electrons of the particles are converted to light. The collisions of different particles result in different
colored lights. Atomic oxygen produces red and green lights, nitrogen produces pink, blue, or violet light,
helium produces purple lights and neon produces rippled orange light. Auroras come in a vast array of
shapes and forms such as arcs, swirls, “curtains” and glowing shapes. They often appear to be moving.
Auroras often occur as a result of a geomagnetic storm. A geomagnetic storm is the temporary
disturbance of the Earth’s magnetic field as a result of an event in space such as a solar flare or coronal
mass ejection (the ejection of charged particles from the sun’s corona). In noteworthy geomagnetic
storms, Auroras can be seen well south (or north) of where they usually occur. The famous Great
Geomagnetic Storms of 1859 produced what witnesses call the most spectacular auroras ever seen. Such
auroras were seen throughout the United States, Japan, and Australia. The event lasted for almost a week.
Which of the following is a necessary element for an aurora?
Aa stream of polar wind
Bsolar collision with charged particles
Cthe conversion of kinetic energy正確答案
Dthe far-travelling corona of the sun
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