2015-02-27
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Helical fluid motions in the Earth's electrically conducting liquid outer core have an electromagnetic dynamo effect, giving rise to the Earth's magnetic field. The Earth's sizable, hot core, along with the planet's rapid spin, probably accounts for the exceptional strength of the magnetic field of the Earth as compared with those of the other terrestrial planets.
An important characteristic of the Earth's magnetic field is polarity reversal. In this process the direction of the dipole component reverses— e.g., the north pole becomes the south. Reversals occur unpredictably at intervals that may range from tens of thousands of years to millions of years. The mechanisms by which a changeover occurs remains uncertain. It is likely that a nondipolar field remains, at a small fraction of the strength of the normal field.
The Earth's main magnetic field permeates the planet and an enormous volume of space surrounding it. A great teardrop-shaped region of space called the magnetosphere is formed by the interaction of the Earth's field with the solar wind composed of charged particles (plasma) that streams outward from the Sun. At a distance of about 60,000 kilometres outward toward the Sun, the pressure of the solar wind is balanced by the geomagnetic field. This serves as an obstacle to the solar wind, and the plasma is deflected around the Earth by the resulting bow shock. The magnetosphere so produced streams out into an elongated magnetotail that stretches several million kilometres downstream from the Earth away from the Sun.
Solar wind plasma particles can leak through the magnetopause, the boundary of the magnetosphere, and populate its interior; charged particles from the ionosphere also enter the magnetosphere. The magnetotail can store an enormous amount of energy—several billion megajoules—for hours. This occurs through a process called reconnection, in which the interplanetary magnetic field, carried by the solar wind, becomes linked with the magnetic field in the Earth's magnetosphere. The energy is released in dynamic structural reconfigurations of the magnetosphere, called geomagnetic substorms, which often result in the precipitation of energetic particles into the the ionosphere, giving rise to fluorescing auroral displays.
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Converging magnetic field lines fairly close to the Earth can trap highly energetic particles so that they gyrate between hemispheres and slowly drift around the planet in two doughnut-shaped zones known as the Van Allen radiation belts. Many of the particles trapped in these radiation belts are produced by the decay of a neutron into an electron and a proton when energetic cosmic rays strike the Earth's upper atmosphere. The radiation belts were first discovered in 1958 by the American physicist James Van Allen, using instruments aboard the Explorer 1 and 3 satellites. The Earth's magnetosphere has been extensively studied ever since, and space physicists have extended their studies of plasma processes to the vicinities of comets and other planetary systems. In magnetospheric physics, as in most branches of planetary science, the Earth remains the touchstone for comparative planetology.
Vocabulary Notes:
- to harbour life
- crust, core and mantle
- lithosphere - the rigid outer layer of the earth, having an average thickness of about 75 km and comprising the earth's crust and the solid part of the mantle above the asthenosphere, that is a thin semifluid layer of the earth (100-200 km thick), below the outer rigid lithosphere, forming part of the mantle and thought to be able to flow vertically and horizontally, enabling sections of lithosphere to subside, rise, and undergo lateral movement
- atmosphere - the gaseous envelope surrounding the earth or any other celestial body
(a) troposphere - the lowest atmospheric layer, about 18 kilometres (11 miles) thick at the equator to about 6 km (4 miles) at the Poles, in which air temperature decreases normally with height at about 6.5°C per km;
(b) stratosphere - the atmospheric layer lying between the troposphere and the mesosphere, in which temperature generally increases with height;
(c) mesosphere - 1) the atmospheric layer lying between the stratosphere and the thermosphere, characterized by a rapid decrease in temperature with height 2) the solid part of the earth's mantle lying between the asthenosphere and the core;
(d) ionosphere - a region of the earth's atmosphere, extending from about 60 kilometres to 1000 km above the earth's surface, in which there is a high concentration of free electrons formed as a result of ionizing radiation entering the atmosphere from space
- magnetosphere - the region surrounding a planet, such as the earth, in which the behaviour of charged particles is controlled by the planet's magnetic field
- hydrosphere - the watery part of the earth's surface, including oceans, lakes, water vapour in the atmosphere, etc
- bow shock - головная ударная волна (в магнитосфере), головной скачок уплотнения
- Copernican - of or relating to Nicolaus Copernicus, the Polish astronomer (1473-1543)
- Galileo Galilei - Галилео Галилей (выдающийся итальянский математик, физик и астроном; 1564-1642)
- Earth’s curvature - something curved or a curved part of a thing
- Galileo - a US spacecraft, launched 1989, that entered orbit around Jupiter in late 1995 to study the planet and its major satellites
- flat entity
- to be outfitted - to be furnished with an outfit, equipment, etc.
- remote-sensing instruments
- to fly by = to fly over
- en route to = on a journey to
- latitudinal - широтный
- swarm/pile/range/group/mass of artificial satellites
- tawny - рыжевато-коричневый; тёмно-жёлтый
- fraction = fragment – частица
- equatorial circumference - 1) окружность; замкнутая кривая 2) длина окружности; длина замкнутой кривой
- bulge - выпуклость, округлый выступ bulge of a curve — горб кривой (линии)
- oblate - сплющенный (у полюсов)
- pheroid - сфероид (тело, образуемое вращением эллипса вокруг его малой оси; вообще тело, ограниченное поверхностью, похожей на сферу) oblate spheroid — сплющенный сфероид
- helium - гелий
- hydrogen - водород
- argon - аргон (инертный газ)
- suspension – хим. взвешенное состояние; суспензия; взвесь
- aurora, -ras or –rae 1) an atmospheric phenomenon consisting of bands, curtains, or streamers of light, usually green, red, or yellow, that move across the sky in polar regions. It is caused by collisions between air molecules and charged particles from the sun that are trapped in the earth's magnetic field
- doughnut пончик, doughnut-shaped
- Van Allen belt - either of two regions of charged particles above the earth, the inner one extending from 2400 to 5600 kilometres above the earth and the outer one from 13 000 to 19 000 kilometres. The charged particles result from cosmic rays and are trapped by the earth's magnetic field Etymology: named after its discoverer, James Alfred Van Allen (born 1914), US physicist Van Allen belt пояс Ван Аллена
- volatile – 1) летящий; летающий, способный летать 2) непостоянный, изменчивый; неуловимый, переменный
- alloy – сплав
Tasks:
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1. Make up a list of words and word combinations that present a difficulty in proper pronunciation. Make sure you pronounce these items correctly.
2. Make up 15 sentences (for translation) with the active vocabulary.
3. Pick out “space terms” from the text, arrange them into thematic groups.
4. Translate into Russian the following statements:
a) Scientists have applied the full battery of modern instrumentation to studying the Earth in ways that have not yet been possible for the other planets; thus, much more is known about its structure and composition.
b) In December 1990 the Galileo spacecraft, outfitted with an array of remote-sensing instruments, studied the Earth during the first of its two gravity-assisted flybys en route to the planet Jupiter.
c) The Moon is one of the bigger natural satellites in the solar system and is in fact relatively large compared with the Earth itself.
d) The Earth is surrounded by a relatively thin atmosphere consisting of a mixture of gases, primarily molecular nitrogen (77 percent) and molecular oxygen (21 percent).
e) Most of the atmosphere is concentrated in the troposphere, which extends from the surface to an altitude of about 15 kilometres.
f) Volcanic explosions, such as the 1991 eruption of Mount Pinatubo in the Philippines, can inject great quantities of particulates into the stratosphere, which remain suspended for years, decreasing atmospheric transparency and resulting in measurable cooling worldwide.
g) In terms of percentage, atmospheric water vapour is negligible, but the transport of water evaporated from the oceans onto land surfaces is an integral part of the hydrologic cycle that renews and sustains the ecosphere.
h) More than 90 percent of the Earth's mass is composed of iron, oxygen, silicon, and magnesium, elements that can form the crystalline minerals known as silicates. However, in terms of chemical and mineralogical composition, as in physical properties, the Earth is far from homogeneous.
5. What important historic facts were touched upon in the article? What do you personally know about the Copernican revolution, Galileo’s telescope, Apollo 8?
6. Name the most prominent spherical zones.
7. Speak on the Earth’s image.
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