Solar Eruptions

Coronal mass ejections, or CMEs, are powerful eruptions that can blow up to 10 billion tons of the sun's atmosphere into interplanetary space. Traveling away from the sun at speeds of approximately one million mph, CMEs can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with Earth. Large geomagnetic storms can cause electrical power outages and damage communications satellites.

CMEs are often associated with solar flares and prominence eruptions, but they can occur when neither is present.

	Prominences, like these observed by STEREO, are loops of magnetic fields with hot gas trapped inside. Sometimes, they erupt and quickly rise off the sun as the fields become unstable. They become more common as we approach solar maximum. + Read More
Despite the importance of CMEs, scientists don't fully understand the origin and evolution of CMEs, nor their structure or extent in interplanetary space. STEREO's unique 3-D images of the structure of CMEs will enable scientists to determine their fundamental nature and origin.
	Ground- and space-based instruments called coronagraphs produce an artificial eclipse of the sun by placing a "disk" over the sun's image. This allows scientists to see solar events, such as the coronal mass ejections visible in this image to the left and right sides of the disk. Click here to view mpeg (271 KB).