An Oct. 28, 2003 eruption created a monstrous solar flare – the third largest recorded since 1976 – and an associated coronal mass ejection, in which superheated gas, called plasma, streaks away from the sun at millions of miles an hour. When the plasma hits the Earth it can disrupt the planet’s magnetic field, triggering a geomagnetic storm. The geomagnetic storm associated with this event began at about 4 a.m. Oct. 29 and reached the highest level for such storms – G5 on a scale that starts at G1 – for about three hours before decreasing, according to John Kohl, a solar astrophysicist at the Harvard-Smithsonian Center for Astrophysics. Kohl is the principal investigator for the Ultraviolet Coronagraph Spectrometer on board NASA’s Solar and Heliospheric Observatory spacecraft (SOHO) The event could provide some insights as to the sun’s magnetic nature, Kohl said. Immediately after the enormous eruption, scientists saw material not only moving toward the Earth, but also moving away from it, as if the force of the explosion blew the magnetic field back, away from the Earth, pulling some material with it. “I think we’re going to learn about magnetic fields during this event,” Kohl said.