CORONAL MASS EJECTIONS [CME] Coronal Mass Ejections (CMEs) are large expulsions of plasma and magnetic field from the Sun’s corona. They can eject billions of tons of coronal material and carry an embedded magnetic field (frozen in flux) that is stronger than the background solar wind interplanetary magnetic field (IMF) strength. CMEs travel outward from the Sun at speeds ranging from slower than 250 kilometers per second (km/s) to as fast as near 3000 km/s. The fastest Earth-directed CMEs can reach our planet in as little as 15-18 hours. Slower CMEs can take several days to arrive. They expand in size as they propagate away from the Sun and larger CMEs can reach a size comprising nearly a quarter of the space between Earth and the Sun by the time it reaches our planet.

GEOMAGNETIC STORM WATCH (G1): Yesterday's "canyon of fire" CME (described below) could graze our planet's magnetic field on March 20th. If so, the timing would be perfect for equinox auroras. At this time of year, even a glancing blow from a CME can spark geomagnetic storms thanks to the springtime Russell-McPherron effect. CANYON OF FIRE ERUPTION: A large filament of magnetism stretching across the sun's southern hemisphere erupted on March 17th, carving a "canyon of fire" in the sun's atmosphere. NASA's Solar Dynamics Observatory (SDO) recorded the blast. Debris from the explosion produced a partial halo CME seen here in a SOHO coronagraph movie. A NASA model of the storm cloud suggests it could strike Earth's magnetic field on March 20th, sparking high-latitude auroras on the first night of Northern Spring. spaceweather.com