The solar wind is powerful and is believed to have eroded or stripped away the atmospheres of other planets such as Mercury. Earth's relatively strong magnetic and gravitational fields have preserved its atmosphere from the constant onslaught. Observers near the poles sometimes see beautiful lights in the night sky known as auroras, the result of the solar wind interacting with Earth's magnetic field and atmosphere.
Photo: A coronal mass ejection, which is a type of violent solar plasma eruption that disrupts the solar wind (ESA/NASA)
Charged particles race across the Solar System.
Sir Patrick Moore's guests discuss Saturn's magnetic field and storms.
Sir Patrick Moore spoke to his guests, Professor John Zarnecki from the Open University and Professor Michele Dougherty from Imperial College, about Saturn's core, magnetic field and storms shortly after the Cassini-Huygens probe reached the ringed planet in 2004.
A stream of particles from the Sun stretches beyond the outer planets.
Measurements made by the 1962 Mariner 2 spacecraft confirmed the presence of solar wind, a stream of particles from the Sun that stretches far beyond the outer planets. The Earth's magnetic field fights a constant battle against the solar wind's atmosphere eroding effects.
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists of mostly electrons, protons and alpha particles with energies usually between 1.5 and 10 keV; embedded in the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona and magnetic, electrical and electromagnetic phenomena within it.
At a distance of more than a few solar radii from the sun, the solar wind is supersonic and reaches speeds of 250 to 750 kilometers per second. The flow of the solar wind is no longer supersonic at the termination shock. The Voyager 2 spacecraft crossed the shock more than five times between 30 August and 10 December 2007. Voyager 2 crossed the shock about a billion kilometers closer to the Sun than the 13.5 billion kilometer distance where Voyager 1 came upon the termination shock. The spacecraft moved outward through the termination shock into the heliosheath and onward toward the interstellar medium. Other related phenomena include the aurora (northern and southern lights), the plasma tails of comets that always point away from the Sun, and geomagnetic storms that can change the direction of magnetic field lines.