36.9 MB (3.8 MB compressed)
4373 x 2951 pixels
37.1 x 24.9 cm ⏐ 14.6 x 9.8 in (300dpi)
PEKKA PARVIAINEN / SCIENCE PHOTO LIBRARY PEKKA PARVIAINEN / SCIENCE PHOTO LIBRARY
View of a colourful aurora borealis display (northern lights). Aurorae are caused by the interaction between energetic charged particles coming from the Sun and molecules of gases in the upper atmosphere (about 100km). A stream of charged particles, known as the solar wind, flows continuously from the Sun's corona towards interplanetary space at speeds of 400-500 km/s. These particles do not reach the Earth's atmosphere due to the shielding effect of the Earth's magnetic field. However, violent solar activities such as solar flares emit highly energetic particles which penetrate this shield and ionise molecules in the atmosphere.
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