The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time. These particles can escape the Sun's gravity because of their high kinetic energy and the high temperature of the corona.

The solar wind creates the heliosphere, an enormous bubble in the interstellar medium that surrounds the Solar System. Other related phenomena include geomagnetic storms that can knock out power grids on Earth, the aurora (northern and southern lights), and the plasma tails of comets that always point away from the Sun.