The solar wind is a stream of charged particles flowing out from the sun’s outer atmosphere or corona. It blows at speeds of about 400-500 kilometres per second and on an average takes 4-5 days to reach the vicinity of the earth. It consists mainly of elementary particles such as protons and electrons in roughly equal numbers, together with heavier particles such as alpha particles (helium nuclei). Violent events in the sun’s atmosphere such as flares and prominences send bursts of high speed particles singing through the slower moving wind. The sun loses more than a million tonnes of matter per second into the solar wind. This may appear to be alarming, but it is an infinitesimal quantity compared to the mass of the sun and so there is no danger of the fading away of the sun due to solar winds.
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