Magnetosphere

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Magnetosphere

The magnetosphere is a region around an astronomical body where the behavior of charged particles is strongly influenced by magnetic and ionic phenomena. The magnetosphere around Earths outer atmosphere is comet-shaped. The planets Jupiter, Saturn, Uranus, and Neptune also have magnetospheres. Mercury, and Ganymede, one of Jupiters moons, have very weak magnetospheres, while Mars has an irregular magnetosphere. The term was first introduced by Austrian-born British astronomer and astrophysicist Thomas Gold (19202004) in 1959 although speculation about the existence of such a region goes back to the early 1930s in the studies of Sydney Chapman and V.C.A. Ferraro. The discovery of Earths magnetosphere was discovered in 1958 by astronomers researching through the spacecraft Explorer I.

The magnetosphere exists because of the interaction between the Earths own magnetic field and the solar wind, a rapidly moving plasma consisting of protons and electrons expelled from the suns surface. The magnetospheres distinctive shape is a consequence of the fact that the solar wind is deflected by Earths magnetic field in a manner somewhat similar to the way a rock deflects the flow of a stream of water.

The forward (sun-facing) edge of the magnetosphere is located at a distance of about ten Earth radii (about 40,365 mi/65,000 km) from Earths surface. At this distance, the pressure of particles escaping from Earths atmosphere is equal to the pressure of the solar wind. An equilibrium layer with a thickness of about 62 mi (100 km) in this region is known as the magnetopause. The magnetopause completely surrounds the magnetosphere like a thin envelope. Forward of the magnetopause in the direction of the sun is the magnetosheath, a region in which Earths magnetic field is highly turbulent.

The magnetosphere extends much farther from Earth on the side away from the sun (the night side) because both the solar wind and particles escaping from Earths atmosphere are moving in the same direction. It appears that the magnetopause in this direction may be located at a distance of a few thousand Earth radii.

The internal structure of the magnetopause is highly complex. The reason for this complexity is that three distinct factorsthe solar wind, Earths magnetic field, and the suns magnetic fieldare constantly interacting with each other. This interaction causes the development of distinct regions within the magnetosphere. For example, the night side of the magnetosphere appears to be subdivided into two regions by a thin layer of plasma called the plasma sheet.

Certain familiar astronomical phenomena are related to the magnetosphere. For example, particles excited by the interaction between the solar wind and the magnetosphere may eventually collide with and ionize particles in the upper atmosphere. When these ionized particles return to their ground state, they give off energy that may appear in the form of auroras (aurora borealis or aurora australis).

views updated

Magnetosphere

The magnetosphere is a comet-shaped region of Earth's outer atmosphere in which the behavior of charged particles is strongly influenced by magnetic and ionic phenomena. The term was first introduced by the British astronomer Thomas Gold in 1959 although speculation about the existence of such a region goes back to the early 1930s in the studies of Sydney Chapman and V.C.A. Ferraro.

The magnetosphere exists because of the interaction between Earth's own magnetic field and the solar wind , a rapidly moving plasma consisting of protons and electrons expelled from the sun's surface. The magnetos phere's distinctive shape is a consequence of the fact that the solar wind is deflected by Earth's magnetic field in a manner somewhat similar to the way in which a rock deflects the flow of a stream of water .

The forward (sun-facing) edge of the magnetosphere is located at a distance of about ten Earth radii (about 40,365 mi/65,000 km) from the Earth's surface. At this distance, the pressure of particles escaping from Earth's atmosphere is equal to the pressure of the solar wind. An equilibrium layer with a thickness of about 62 mi (100 km) in this region is known as the magnetopause. The magnetopause completely surrounds the magnetosphere like a thin envelope. Forward of the magnetopause in the direction of the Sun is the magnetosheath, a region in which Earth's magnetic field is highly turbulent.

The magnetosphere extends much farther from Earth on the side away from the Sun (the "night" side) because both the solar wind and particles escaping from Earth's atmosphere are moving in the same direction. It appears that the magnetopause in this direction may be located at a distance of a few thousand Earth radii.

The internal structure of the magnetopause is highly complex. The reason for this complexity is that three distinct factors—the solar wind, Earth's magnetic field, and the Sun's magnetic field—are constantly interacting with each other. This interaction causes the development of distinct regions within the magnetosphere. For example, the night side of the magnetosphere appears to be subdivided into two regions by a thin layer of plasma called the plasma sheet.

Certain familiar astronomical phenomena are related to the magnetosphere. For example, particles excited by the interaction between the solar wind and the magnetosphere may eventually collide with and ionize particles in the upper atmosphere. When these ionized particles return to their ground state, they give off energy that may appear in the form of auroras (aurora borealis or aurora australis).

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magnetosphere The space around a planet in which ionized particles are affected by the planet's magnetic field. The Earth's magnetosphere reaches far beyond the atmosphere. In the magnetosphere, charged particles are concentrated at altitudes of about 3000 km and 16 000 km. The charged particles oscillate between the northern and southern hemispheres. The outer boundary of the magnetosphere is sharp and well defined, extending to about 10 Earth radii on the sunlit side of the Earth and to perhaps 40 Earth radii on the dark side; but the boundary changes its position in response to solar activity, being depressed by the solar wind. See also EXOSPHERE; and IONOSPHERE.

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magnetosphere The space around a planet in which ionized particles are affected by the planet's magnetic field. The Earth's magnetosphere reaches far beyond the atmosphere. In the magnetosphere, charged particles are concentrated at altitudes of about 3000 km and 1600 km. The charged particles oscillate between the northern and southern hemispheres. The outer boundary of the magnetosphere is sharp and well defined, extending to about 10 Earth radii on the sunlit side of the Earth and to perhaps 40 Earth radii on the dark side; but the boundary changes its position in response to solar activity, being depressed by the solar wind. See also exosphere and ionosphere.