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Glossary of Solar-Terrestrial Terms | Solar, Earth Atmospheric and Climate Gallery
The changing position of a comet's tail as it circumnavigated the sun lead observers to predict a solar wind , something blowing out from the sun causing long streamers behind the comet just as a strong wind causes long hair to blow away from a face. This wind was confirmed in 1959 by the Soviet Luna 3 spacecraft and has been the object of study ever since.
The solar wind consists of charged particles, mainly protons and electrons, emanating from the Sun in all directions at speeds of several hundred kilometers per second and carries a magnetic field. The solar wind also contains, in much smaller amounts, positive ions stripped of many of their electrons by the extremely high temperatures of the Sun.
The very active, very hot corona continually expands outward moving at velocities of hundreds of kilometers per second, a million miles per hour! This allows these protons and electrons to escape the gravity of the sun and pour out into space well beyond the solar system. The Earth's magnetic field (magnetosphere) protects us from these particles, acting like a rock in a stream, diverting the solar wind around us.
The solar wind reaches earth if a break is created in the magnetosphere due to the magnetic field orientation of the solar wind being directly opposite to that of the Earth. At that time there is a momentary opening of the magnetosphere that protects us and some solar wind leaks in.
The solar wind is less energetic than galactic wind (cosmic radiation) by orders of magnitude and can be identified by these energetic differences. Solar wind energies are 1-2 keV (thousand electron volts) per nucleon. A large eruption from the sun (Coronal Mass Ejection, CME) could produce solar particles with energies of 10 MeV (million electron volts). Cosmic radiation energies are in excess of several billion electron volts.