Even at its most quiescent, the sun hurls into space a billion-ton cloud of charged particles every 2 days or so. The few particles that strike our planet can disrupt satellites and knock out power systems on the ground.
Twin spacecraft have for the first time tracked these storms, known as coronal mass ejections, from their birth in the lower depths of the sun's atmosphere all the way to Earth's orbit, scientists announced this week. The new capability will enable solar physicists to forecast the terrestrial arrival time of the storms with an uncertainty of just 3 hours, one-quarter the uncertainty of previous estimates, says Russ Howard of the Naval Research Laboratory in Washington, D.C.
The pair of craft makes up the Solar Terrestrial