Solar Wind, a continuous stream of matter that flows outward from the sun in all directions. The solar wind is composed of electrically charged particlesprimarily electrons and the nuclei of hydrogen and helium atoms. The particles travel away from the sun at speeds of 200 to 600 miles (320 to 960 km) per second. Relatively few of the particles reach the earth's atmosphere, because the earth's magnetic field acts as a barrier. Increases in the intensity of the solar wind are associated with auroras, magnetic storms, and other disturbances in the earth's magnetic field and atmosphere.
The solar wind was first detected in 1959 by spacecraft sent beyond the earth's magnetic field. Scientists had predicted the existence of the solar wind from the fact that a comet's tail always extends away from the sun.