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at 2 50 universal time on july 23 2012

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the sun unleashed an incredibly powerful

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coronal mass ejection or cme

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a cme is a huge cloud of plasma that

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bursts out of the sun's atmosphere and

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is held together with magnetic fields

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an average cme travels at about 1

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million miles per hour and weighs around

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2 trillion tons

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on this particular monday however the

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sun unleashed a perfect storm of plasma

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thanks to nasa's far-ranging

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heliophysics fleet we have an excellent

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picture of the event

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the incredibly high resolution view of

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the sun provided by nasa's solar

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dynamics observatory or sdo revealed the

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beginning of the eruption in several

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different wavelengths of ultraviolet

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nasa's twin stereo spacecraft orbiting

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the sun ahead and behind earth

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gave a similar view from alternate

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the stereo satellites also carry

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coronagraphs which block the bright

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solar disk to make the fainter extended

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solar atmosphere or corona visible

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as a result they were able to image the

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actual cme as it left the sun

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the cme headed in the direction of the

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stereo a spacecraft at an astonishing

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as the cme arrived at stereo a

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the coronagraph and stereo's wider field

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heliospheric imagers were pummeled by

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high energy particles which appear like

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snow in the imagery

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the joint esa and nasa solar and

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heliospheric observatory or soho that

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has been observing the sun since 1995

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captured footage of the cme in both of

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its coronagraphs which overlap their

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all of these data allow computer models

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to reconstruct the full shape and

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expansion of the cme

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the main event is preceded by a few

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smaller cmes one of which was earth

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directed

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it is immediately clear how much larger

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and faster the july 23rd cme was as it

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blasted towards stereo a

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nasa's fleet of heliophysics spacecraft

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watching the sun from all sides improves