Table of Contents
BEST IELTS General Reading Test 236
BEST IELTS General Reading Test 236 – PASSAGE – 3
IELTS GENERAL READING TEST
READING PASSAGE – 3
The Auroras
An aurora occasionally referred to as polar lights, northern lights (aurora borealis), or southern lights (aurora Australis), is a natural light exhibition in the Earth’s sky, largely seen in the high- latitude regions (around the Arctic and Antarctic). Auroras are the result of turbulences in the magnetosphere activated by solar wind. These turbulences are sometimes stout enough to change the courses of charged particles in both solar wind and magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere(thermosphere/exosphere. The subsequent ionization and excitation of atmospheric constituents produce light of changing colour and complexity. The form of the aurora, happening within bands around both polar regions, is also reliant on the amount of acceleration informed to the precipitating particles. Precipitating protons usually produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are usually observed at lower latitudes.
The Word “aurora” is derivative from the name of the Roman goddess of the dawn, Aurora, who travelled from east to west announcing the coming of the sun. Ancient Greek poets used the name metaphorically to denote to dawn, often stating its play of colors across the otherwise dark sky. Most auroras happen in a band known as the “auroral zone”, which is typically 3° to 6° wide in latitude and between 10° and 20° from the geomagnetic poles at all local times (or longitudes), most evidently seen at night against a dark sky. A region that presently displays an aurora is called the “auroral oval”, a band exiled towards the night side of the Earth.
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Early indication for a geomagnetic connection comes from the statistics of auroral observations. Elias Loomis (1860), and later Hermann Fritz (1881) and Sophus Tromholt (1881) in more detail, established that the aurora looked mainly in the auroral zone. Day-to-day positions of the auroral ovals are posted on the Internet. In northern latitudes, the effect is known as the aurora borealis or the northern lights. The previous term was coined by Galileo in 1619, from the Roman goddess of the dawn and the Greek name for the north wind. The southern counterpart, the aurora Australis, or the southern lights, has features almost identical to the aurora borealis and changes concurrently with changes in the northern auroral zone. The aurora Australis is observable from high southern latitudes in Antarctica, Chile, Argentina, New Zealand, and Australia.
A geomagnetic storm grounds the auroral ovals (north and south) to expand, bringing the aurora to lower latitudes. The rapid distribution of auroras (“auroral oval”) is slightly different, being cantered about 3-5° night ward of the magnetic pole, so that auroral arcs reach furthest toward the equator when the magnetic pole in question is in between the observer and the Sun. The aurora can be seen finest at this time, which is called magnetic midnight.
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Auroras seen inside the auroral oval may be directly overhead, but from farther away, they brighten the poleward horizon as a greenish glow, or sometimes a faint red, as if the Sun were growing from an unfamiliar direction. Auroras also happen poleward of the auroral zone as either diffuse patches or arcs, which can be sub visual.
Colours and wavelengths of auroral light
Red: At the highest elevations, excited atomic oxygen emits at 630 nm (red); low concentration of atoms and lower sensitivity of eyes at this wavelength make this color visible only under intense solar activity. The low number of oxygen atoms and their gradually diminishing concentration is responsible for the faint appearance of the top parts of the “curtains”. Scarlet, crimson, and carmine are the most often-seen hues of red for the auroras.
Green: At lower heights, the more frequent collisions suppress the 630-nm (red) mode: rather the 557.7 nm emission (green) dominates. A high concentration of atomic oxygen and higher eye sensitivity in green make green auroras the most common. The excited molecular nitrogen (atomic nitrogen being rare due to the high stability of the N₂ molecule) plays a role here, as it can transfer energy by collision to an oxygen atom, which then radiates it away at the green wavelength. (Red and green can also mix to produce pink or yellow hues.) The rapid decrease of concentration of atomic oxygen below 100 km is responsible for the abrupt- looking end of the lower edges of the curtains. Both the 557.7 and 630.0 nm wavelengths correspond to forbidden transitions of atomic oxygen, a slow mechanism responsible for the graduality (0.7 s and 107 s respectively) of flaring and fading.
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Blue: At lower altitudes, atomic oxygen is uncommon, and molecular nitrogen and ionized molecular nitrogen take over in producing visible light emission, radiating at many wavelengths in both red and blue parts of the spectrum, with 428 nm (blue) being dominant. Blue and purple emissions, typically at the lower edges of the “curtains”, show up at the highest levels of solar activity. The molecular nitrogen transitions are much faster than the atomic oxygen ones.
Ultraviolet: Ultraviolet radiation from auroras (within the optical window but not visible to virtually all humans) has been observed with the requisite equipment. Ultraviolet auroras have also been seen on Mars, Jupiter, and Saturn. Infrared: Infrared radiation, in wavelengths that are within the optical window, is also part of many auroras.
Yellow and pink are a mix of red and green or blue. Other shades of red, as well as orange, may be seen on rare occasions; yellow green is moderately common. As red, green, and blue are the primary colours of additive synthesis of colours, in theory, practically any colour might be possible, but the ones mentioned in this article comprise a virtually exhaustive list.
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QUESTION 27-33
Do the following statements agree with the information given in the Reading Passage?
TRUE If the statement agrees with the information
FALSE If the statement contradicts the information
NOT GIVEN If there is no information on this
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27. Auroras are the consequence of commotions in the magnetosphere triggered by solar wind.
28. The charged particles are primarily electrons and protons which travels hastily into the upper atmosphere.
29. It is believed that the Roman goddess Aurora created the Auroras.
30. Few auroras transpire in a band known as the “auroral zone”.
31. In northern latitudes, the aurora effect is recognized as the aurora borealis or the northern lights.
32. The Australis aurora emerges in several provinces including Antarctica.
33. Magnetic midnight is the ideal time to witness auroras.
IELTS General Reading Test
QUESTION 34-40
Complete the fill ups below.
Write no more than TWO WORDS or NUMBERS for each answer
34. Red colour in auroras can be seen at the altitude.
35. Red colour is only visible when the ………….. is powerful.
36. Green colour is visible at elevation.
37. Green colour auroras are most common due to the extraordinary cluster of
38. At inferior heights, atomic oxygen is ……..
39. …………….. auroras have been witnessed on other planets.
40. Hypothetically, ……………… colour of aroura is probable
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ANSWERS ARE BELOW
IELTS General Reading Test
ANSWERS
27. TRUE
28. TRUE
29. NOT GIVEN
30. FALSE
31. TRUE
32. TRUE
33. TRUE
34. HIGHEST
35. SOLAR ACTIVITY
36. LOWER
37. ATOMIC OXYGEN
38. UNCOMMON
39. ULTRAVIOLET
40. ANY
IELTS General Reading Test