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The origin of the solar wind

It was the observation of the tail of comets that made it suspected that the Sun could emit a continuous stream of particles of high energy. In 1962 the space probe Mariner 2 brought the proof. The solar wind has its source in the solar corona which is the "atmosphere" of the Sun (it is the interface between the Sun and the interplanetary environment).

The nature of the solar wind

The solar wind is a plasma totally ionised, consisted of particles (protons and electrons) independent from one another. These particles, the fastest, have a speed which allows them to escape the solar gravity. The composition of this plasma is identical to that of the solar corona: 73 % hydrogen and 25 % helium. Here, the density is weak (about ten protons by cm3 or less). Due to its nature the solar wind is the origin of a magnetic field which will affect the environment of the Earth and the entire solar system.

The comet tail is created by the interaction of the solar wind particles with the gas of the head of the comet.