Beautiful lights sometimes seen in the night sky in northern and southern regions of the Earth are caused by the interaction of the solar wind - a stream of charged particles escaping the Sun - and our planet's magnetic field and atmosphere.
The Earth's magnetic field traps some of the particles and sends them on a collision course with molecules in the atmosphere. As a result of these repeated, tiny crashes, energy is released in the form of light.
Photo: Saturn's aurora taken by the Hubble Space Telescope (NASA, ESA, J. Clarke and G. Bacon)
The solar wind's assault on the Earth can be easily seen.
Brian Cox travels to Norway to see the Northern Lights.
Professor Brian Cox travels to Norway in search of the Aurora Borealis, or Northern Lights. Astrophysicist Professor Mike Lockwood accompanies him as they wait for the dazzling display brought by the solar wind.
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.
An aurora is a natural light display in the sky (from the Latin word aurora, "sunrise" or the Roman goddess of dawn), predominantly seen in the high latitude (Arctic and Antarctic) regions.[nb 1] Aurorae are caused by cosmic rays, solar wind and magnetospheric plasma interacting with the upper atmosphere (thermosphere/exosphere). Their charged particles, mainly electrons and protons, enter the atmosphere from above causing ionization and excitation of atmospheric constituents, and consequent light emissions. Auroras caused by protons are sometimes referred to as proton arcs. Incidental protons can also produce emissions as hydrogen atoms after gaining an electron from the atmosphere.