The most powerful solar storm in more than two decades struck Earth on Friday, triggering spectacular celestial light shows from Tasmania to Britain -- and threatening possible disruptions to satellites and power grids as it persists into the weekend. The first of several coronal mass ejections (CMEs) -- expulsions of plasma and magnetic fields from the Sun -- came just after 1600 GMT, according to the National Oceanic and Atmospheric Administration (NOAA)'s Space Weather Prediction Center.