CME TARGETS MARS, EARTH: New sunspot 1387 erupted during the late hours of Christmas Day, producing an M4-class flare and hurling a CME toward Earth and Mars. Click to view an animated forecast track prepared by analysts at the Goddard Space Weather Lab:

The CME is expected to deliver a glancing blow to Earth’s magnetic field on Dec. 28th at 1200 UT and a direct hit to the planet Mars on Dec. 30th at 1800 UT. Using onboard radiation sensors, NASA’s Curiosity rover might be able to sense the CMEwhen it passes the rover’s spacecraft en route to Mars. Here on Earth, NOAA forecasters estimate a 30-to-40% chance of geomagnetic storms on Dec. 28th when the CME and an incoming solar wind stream (unrelated to the CME) could arrive in quick succession. High-latitude sky watchers should be alert for auroras on Wednesday night. 

UPDATE: The chances of a geomagnetic storm on Dec. 28th improved today when a second CME left the sun, this one even more squarely directed toward Earth. Ananimated forecast track shows the cloud reaching our planet on Dec. 28th at 20:22 UT.

fr/spaceweather.com