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Saturday 30 January 2016

X-ray Aurora above Earth....

Above: The surprising view of an violently X-ray emitting aurora, that the INTEGRAL space craft got. Courtesy of ESA

ESA’s INTEGRAL space telescope usually looks into deep space at x ray sources, like black holes and neutron stars. But in November it got a surprise: As it turned to map a section of deep spacer in X-rays it saw a powerful X-ray emission coming from somewhere else: Earth's atmosphere.
The blast of X-rays was coming from the polar regions, where a storm of high energy particles from the Sun was crashing into our upper atmosphere, causing Aurora - these huge curtains of light in the polar sky:

As the high speed particles of a solar storm are funnelled by Earths magnetism into the atmosphere over the poles, different molecules and atoms  in the atmosphere glow like a flourescent tube to create these curtains,  typically in green and red. But auroras also emit X-rays, generated as the incoming particles decelerate - and on this occasion they shone so brightly in X-rays they blotted out the cosmic sources Integral was set to map.
That said the observations weren't a waste: The Earth's magnetic field and how interacts with the solar wind and storms is a source of mysteries to science - which is great, because it means we can use the space around Earth as a huge laboratory to test our theories on magnetism, plasma, and electricity. In fact whole fleets of unmanned probes have been launched to do just that.

Above: Results from ESA's SWARM mission, a fleet of space craft studying Earth's magnetic field.

What Integral saw will help NASA understand the pattern of electrons raining into Earth’s upper atmosphere, and they reveal interactions between the solar wind and Earth’s protective magnetic bubble. “Auroras are transient, and cannot be predicted on the timeframe that satellite observations are planned, so it was certainly an unexpected observation,” comments Erik Kuulkers, Integral project scientist. “Although the original background X-ray measurements didn’t go quite to plan this time, it was exciting to capture such intense auroral activity by chance.”

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