Coronal Mass Ejections

About Coronal Mass Ejections

A Coronal Mass Ejection (CME) is a massive eruption of magnetized plasma from the Sun's corona into interplanetary space. Unlike solar flares, which are bursts of radiation, CMEs are physical clouds of solar material — billions of tons of plasma threaded with magnetic field lines — ejected at speeds ranging from 250 km/s (slow) to over 3,000 km/s (extremely fast). CMEs are often associated with solar flares and filament eruptions. When a CME is directed toward Earth (called a "halo CME" because it appears to surround the Sun in coronagraph images), it can trigger geomagnetic storms upon arrival 1 to 3 days later. Scientists analyze CME properties including speed, angular width (half-angle), type (S = slow, C = common, O = other), and whether it is likely to impact Earth. The SOHO and STEREO spacecraft provide coronagraph imagery used to detect and track CMEs.