Solar flare seen by SOHO

Solar storm hits the Earth

25 January 2012

A large solar flare, at 03:59 GMT on Monday, triggered a coronal mass ejection (CME) travelling at 1400 km/s that reached the Earth in the afternoon of 24 January. The impact of the CME caused a minor geomagnetic storm, but no effects on ground infrastructure such as power grids or phone networks were detected. The main impact of this storm was to trigger spectacular auroral displays at high latitudes.

A coronal mass ejection (CME) is a huge cloud of magnetised plasma from the Sun's atmosphere – the corona – thrown into interplanetary space. They often occur in association with a solar flare. This ejection was detected by the ESA/NASA SOHO and NASA Stereo spaceborne solar observatories. CMEs can produce geomagnetic storms when they reach Earth, between two and six days after leaving the Sun.

The solar flare on Monday morning also triggered the strongest stream of protons seen since 2005. This stream reached the Earth on Monday morning and continued on Tuesday. As an energetic eruption of this level can disrupt satellites, for 48 hours operation teams at ESA were on high alert to monitor the storm. Today, they report no incident. While the flare was stronger than the average and the proton storm was the first strong one in seven years, these events do not have impact at the ground level on Earth. Solar flares and proton events are mainly of concern to satellite operators and they are also closely monitored by the astronauts onboard the International Space Station (ISS).

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