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...comet. When it is even closer to the Sun, solar radiation usually blows the dust of the coma away from the head and produces a dust tail, which is often rather wide, featureless, and yellowish. The solar wind, on the other hand, drags ionized gas away in a slightly different direction and produces a plasma tail, which is usually narrow with nods and twists and has a bluish appearance.
in comet: Cometary tails )...with the photoionization of parent molecules, but the mechanism that produces ions is not yet quantitatively understood. In 1951 the German astronomer Ludwig Biermann predicted the existence of the solar wind (see above) in order to account for the rapid accelerations observed in plasma tails as well as their aberration (i.e., deviation from the direction directly opposite the Sun). The...
The orbits of interplanetary dust particles are easily altered by interaction with the light and charged particles (solar wind) that emanate from the Sun. The smallest particles, less than 0.5 micrometre (μm; 0.00002 inch) in size, are blown out of the solar system. Drag effects from sunlight and the solar wind cause larger particles to spiral toward the Sun, some on paths that intercept...
The solar wind is a flow of completely ionized gas—ions (chiefly protons) and electrons—that continuously expands outward through the solar system from the Sun’s corona. Its density decreases with distance from the Sun; at the distance of Earth’s orbit, it has a density of about 5 particles per cubic cm (0.06 cubic inch). This outflow of plasma transports the magnetic fields of...
A fascinating and scientifically important property of lunar soils is the implantation of solar wind particles. Unimpeded by atmospheric or electromagnetic effects, protons, electrons, and atoms arrive at speeds of hundreds of kilometres per second and are driven into the outermost surfaces of soil grains. Lunar soils thus contain a collection of material from the Sun. Because of their...
in Moon: Lunar resources )The solar wind has implanted hydrogen, helium, and other elements in the surfaces of fine grains of lunar soil. Though their amounts are small—they constitute about 100 parts per million in the soil—they may someday serve as a resource. They are easily released by moderate heating, but large volumes of soil would need to be processed to obtain useful amounts of the desired...
...high latitudes. The field departs from this ideal dipolar configuration, however, at high altitudes. There the terrestrial field, Earth’s magnetic field, is distorted to a significant extent by the solar wind, with its embedded solar magnetic field. Ultimately the terrestrial field is dominated by the interplanetary field, which is generated by the Sun.
in magnetosphere )...65,000 km, or 40,000 miles), the magnetic field is so weak that the pressure associated with particles escaping from the Earth’s gravity is comparable to the opposing pressure associated with the solar wind—the flux mainly of protons and electrons escaping from the Sun’s gravitational field. This equilibrium region, with a characteristic thickness of 100 km (60 miles), is called the...
in astronomy: Planetary studies )Some of the planets have magnetic fields. Earth’s field extends outward until it is disturbed by the solar wind—an outward flow of protons and electrons from the Sun—which carries a magnetic field along with it. Through processes not yet fully understood, particles from the solar wind and galactic cosmic rays (high-speed particles from outside the solar system) populate two...
The solar wind is a collisionless plasma made up primarily of electrons and protons and carries an outflow of matter moving at supersonic and super-Alfvénic speed. The wind takes with it an extension of the Sun’s magnetic field, which is frozen into the highly conducting fluid. In the region of the Earth, the wind has an average speed of 400 kilometres per second; and, when it encounters...
...changing magnetic field creates an electric field, an electromagnetic wave results. Such waves are the slowest and have the lowest frequencies of any known electromagnetic waves. For example, the solar wind streams out from the Sun with a speed greater than either electromagnetic (Alfvén) or sound waves. This means that, when the solar wind hits the Earth’s outermost magnetic field...
At some point after most of the matter in the solar nebula had formed discrete objects, a sudden increase in the intensity of the solar wind apparently cleared the remaining gas and dust out of the system. Astronomers have found evidence of such strong outflows around young stars. The larger debris from the nebula remained, some of which is seen today in the form of asteroids and comets. The...
in solar system: Solution to the angular momentum puzzle )The answer to how this loss could have occurred seems to lie in the solar wind. The Sun and other stars of comparable mass have outer atmospheres that are slowly but steadily expanding into space. Stars of higher mass do not exhibit such stellar winds. The loss of angular momentum associated with this loss of mass to space is sufficient to reduce the rate of the Sun’s rotation. Thus, the...
...the English physicist Sydney Chapman and his student V.C.A. Ferraro, who first suggested its existence. It flows in a single sheet and forms a boundary between the magnetic fields of the Earth and solar wind. When solar wind particles encounter the Earth’s field, they are bent from their paths by the Lorentz force. As noted above, protons gyrate in a left-handed sense around a magnetic field...
in geomagnetic field: Magnetohydrodynamic waves—magnetic pulsations )...of excitation include waves on the magnetopause stimulated by flow of the solar wind, sudden pressure pulses that move the magnetopause in or out, and sudden changes in the flow direction of the solar wind that cause the magnetotail to flap.
The Sun emits not only visible light but also a continuous flow of particles known as the solar wind. Most of these particles are electrically charged and interact only weakly with the atmosphere, because the Earth’s magnetic field tends to steer them around the planet. Prior to the formation of Earth’s iron core and consequent development of the geomagnetic field, however, the solar wind must...
in Earth: The atmosphere )The gases of the atmosphere extend from the surface of Earth to heights of thousands of kilometres, eventually merging with the solar wind—a stream of charged particles that flows outward from the outermost regions of the Sun. The composition of the atmosphere is more or less constant with height to an altitude of about 100 km (60 miles), with particular exceptions being water vapour and...
As is the case for the other planets that have magnetic fields, Uranus’s field repels the solar wind, the stream of charged particles flowing outward from the Sun. The planetary magnetosphere—a huge region of space containing charged particles that are bound to the magnetic field—surrounds the planet and extends downwind from it. On the upwind side, facing the Sun, the...
As the solar wind bombards a planet at supersonic speeds, it generally forms a bow shock on the planet’s sunward side—that is, a standing wave of plasma that slows down, heats, and deflects the flow around the planet. For some planets the bow shock lies at a considerable distance from the surface, held off by the planet’s magnetic field. For example, because of Jupiter’s enormous magnetic...
...a controlling effect (see Earth: The magnetic field and magnetosphere). Of particular and ongoing interest has been the interaction of the flux of charged particles emitted by the Sun, called the solar wind, with the magnetosphere. Early space science investigations showed, for example, that luminous atmospheric displays known as auroras are the result of this interaction, and scientists came...
joint European-U.S. space probe launched in 1990 that was the first spacecraft to fly over the poles of the Sun and return data on the solar wind, the Sun’s magnetic field, and other activity in the Sun’s atmosphere at high solar latitudes. Understanding such solar activity is important not only because the Sun is an average star that is available for close scrutiny but also because its...
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