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.
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.
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.
An aurora is a natural light display in the sky (from the Latin word aurora, "sunrise" or the Roman goddess of dawn), especially in the high latitude (Arctic and Antarctic) regions, caused by the collision of solar wind and magnetospheric charged particles with the high altitude atmosphere (thermosphere). Most auroras occur in a band known as the auroral zone, which is typically 3° to 6° wide in latitude and observed at 10° to 20° from the geomagnetic poles at all local times (or longitudes), but often most vividly around the spring and autumn equinoxes. The charged particles and solar wind are directed into the atmosphere by the Earth's magnetosphere. A geomagnetic storm expands the auroral zone to lower latitudes.
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