The storm, a big cloud of charged particles flung from the Sun at about 4.5 million miles per hour (7.2 million km per hour), was spawned by a pair of solar flares, scientists said.

This is probably the strongest such event in nearly six years, and is likely more intense than a similar storm in late January, said Joseph Kunches, a space weather specialist at the U.S. National Oceanic and Atmospheric Administration NOAA.L.

This solar disturbance is a three-stage affair, or as Kunches said in a telephone interview from Boulder, Colorado: "We hit the trifecta."