Origin of polar auroras revealed

Researchers from UCL, University of Southampton and Cambridge University together with ESA and NASA have uncovered the origin of a colourful display in the night sky called 'theta aurora', explaining for the first time how auroras at high-latitudes form. Auroras are the most visible manifestation of the sun's effect on Earth, but many aspects of these spectacular displays are still poorly understood. The team's findings published in Science today show the role hot plasma, which comprises electrically charged atomic particles, plays in producing the unusual theta aurora. Theta aurora is so named because when seen from above it looks like the Greek letter theta - an oval with a line crossing through the centre. The line is an unusual feature due to the aurora occurring closer to the poles than normal auroras which are found about 65-70 degrees north or south of the equator in an area called the 'auroral oval' and are reasonably well understood by scientists. "The possibilities have been debated since the first satellite observations of the phenomenon were made in the 1980s," said Dr Robert Fear (University of Southampton) who led the study. Although separated by some 93 million miles, the sun and Earth are connected by what's known as the solar wind.