“The sun spit off a big blob of plasma,” Mr. Steenburgh said. The burst of energy, which has its own magnetic field, had been moving through space and reached Earth’s magnetic field on Sunday, when the two collided to create a geomagnetic storm, he said. “It got our magnetosphere pretty revved up.”
When this happens, the aurora can be seen closer to the Equator, Mr. Steenburgh said. Such events are not that uncommon, with about 100 occurring every 11 years, he said, adding that the storm can also disturb high frequency radio used at sea and by airlines.