A large solar flare yesterday triggered a coronal mass ejection travelling at 1400 km/s that will reach Earth today. An energetic eruption of this level can disrupt satellites, so operation teams at ESA and other organisations are closely monitoring the storm.

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.


http://www.esa.int/Our_Activities/Operations/Solar_storm_heading_toward_Earth