Solar wind

:Ion storm redirects here. For information about the games software company, see Ion Storm Inc. For the British comic, see Solar Wind (comic).

History

In 1916, Norwegian researcher Kristian Birkeland was probably the first person to successfully predict that in the Solar Wind, "From a physical point of view it is most probable that solar rays are neither exclusively negative nor positive rays, but of both kinds"; in other words, the Solar Wind consists of both negative electrons and positive ions.

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Three years later in 1919, Frederick Lindemann also suggested that particles of both polarities, protons as well as electrons, come from the Sun.

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Around the 1930s, scientists had determined that the temperature of the solar corona must be a million degrees Celsius because of the way it stood out into space (as seen during total eclipses). Some very clever spectroscopic detective work confirmed this extraordinary temperature. In the mid-1950s the British mathematician

Related Topics:
1930s - Corona - 1950s

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Sydney Chapman calculated the properties of a gas at such a temperature and determined it was such a superb conductor of heat that it must extend way out into space, beyond the orbit of Earth. Also in the 1950s, a German scientist named Ludwig Biermann became interested in the fact that no matter whether a comet is headed towards or away from the Sun, its tail always points away from the Sun. Biermann postulated that this happens because the Sun emits a steady stream of particles that pushes the comet's tail away.

Related Topics:
Sydney Chapman - Ludwig Biermann - Comet

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Eugene Parker realised that the heat flowing from the Sun in Chapman's model and the comet tail blowing away from the Sun in Biermann's hypothesis had to be the result of the same phenomenon. Parker showed that even though the Sun's corona is strongly attracted by solar gravity, it is such a good conductor of heat that it is still very hot at large distances. Since gravity weakens as distance from the Sun increases, the outer coronal atmosphere escapes into interstellar space.

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Opposition to Parker's hypothesis on the solar wind was strong. The paper he submitted to the Astrophysical Journal in 1958 was rejected by two reviewers. It was saved by the editor Subrahmanyan Chandrasekhar (who later received the 1983 Nobel Prize in physics).

Related Topics:
Astrophysical Journal - 1958 - Subrahmanyan Chandrasekhar - 1983 - Nobel Prize

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In January 1959 first ever direct observations and measurements of strength of the solar wind were made by the Soviet satellite Luna 1. However, the acceleration of the fast wind is still not understood and cannot be fully explained by Parker's theory.

Related Topics:
1959 - Soviet - Satellite - Luna 1

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In the late 1990s the UVCS instrument on board the SOHO spacecraft observed the acceleration region of the fast solar wind emanating from the poles of the Sun, and found that the wind accelerates much faster than can be accounted for by thermodynamic expansion alone. Parker's model predicted that the wind should make the transition to supersonic flow at an altitude of about 4 solar radii from the photosphere; but the transition (or "sonic point") now appears to be much lower, perhaps only 1 solar radius above the photosphere, suggesting that some additional mechanism accelerates the solar wind away from the Sun.

Related Topics:
1990s - SOHO - Supersonic - Photosphere

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