An aurora is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). The charged particles originate in the magnetosphere and solar wind are directed by the Earth`s magnetic field into the atmosphere. Most auroras occur in a band known as the aurora zone which is typically 3 to 6 in latitudinal extent and at all local times or longitudes.
Aurora is classified as diffuse or discrete aurora. The diffuse aurora is a featureless glow in the sky which may not be visible to the naked eye even in a dark night and defines the extent of the aurora zone. Discrete aurorae are sharply defined feature within the diffuse aurora which vary in brightness from just barely visible to the naked eye to bright enough to read a newspaper at night .Discrete aurorae are usually observed only in the night sky because they are not as bright as the sunlit sky .
In northern latitudes ,the effect is known as the aurora borealis (or the northern lights ),named after the Roman goddess of dawn, Aurora , and the Greek name for the north wind ,Boreas ,by Pierre Gassendi in 1621.Its southern counterpart , the aurora australis (or the south lights), has almost identical features to the aurora borealis and changes simultaneously with the changes in the northern auroral zone and is visible from high southern latitudes in Antarctica , South America and Australia.
(Soal UN SMA/MA IPA 2011/2012)
1. The following are some facts about aurora EXCEPT ….
A. it is diffuse or discreteB. it is a display of natural lightC. it can be seen in Arctic and AntarcticD. it is always bright enough for you to read a newspaperE. it is caused by the collision of charged particles and atoms in the thermosphere
2. What is the main idea of paragraph2?
A. The diffuse aurora is a featureless glow in the skyB. The discrete aurora are sharply defined features within the diffuse aurora
C. There are two kinds of aurora, diffuse and discrete aurora
D. Discrete aurora are usually observed only in the night sky
E. Discrete aurora are the not as bright as sunlit sky
3. We know from the text that ….
A. An aurora is very beautifulB. Aurorae can be seen in the north and south polesC. Aurora is named after a roman god
D. Diffuse aurora is sharply definedE. Discrete aurora is more beautiful than diffuse aurora
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