The solar wind is the constant flow of charged particles from the sun. These particles include protons, electrons and some nuclei of heavy elements. They are accelerated by high temperatures of the solar corona or outer region of the sun, to velocities high enough to allow them to escape from the sun’s gravitational field. Recent researches using satellites have shown that the solar winis made up of plasma, i.e. ionized gas, mostly hydrogen and helium, containing nearly an equal number of protons and electrons.
The solar wind streams from the sun though outer space at a speed of about 480 km (300 miles) per second. It takes the particles about 3
days to reach Earth.
In 1958, the American physicist, Egune Norman Parker, called this outward system of protons — the solar wind.
The solar wind causes the tails of comets to change direction and point away from the sun. It also causes magnetic storms which may disrupt radio communications on Earth. The solar wind causes ionization of the gases in an upper atmosphere, resulting in the coloured light phenomena known as auroras.
When the solar wind encounters Earth’s magnetic field a shock wave results, the nature of which is not fully understood. That part of the solar wind which does not interact with Earth or the other planets continues to travel at supersonic speeds upto a distance of approximately 20 astronomical units (one astronomical unit is about 1.5 x 
kms). As it passes through a similar shock phenomenon it loses this supersonic characteristic. Here the gas cools off and eventually diffuses into the galactic space.