Shortly after midnight UTC on Feb. 25 (7:25 p.m. Feb. 24 EST), an intense solar flare sent a powerful burst of radiation out from the sun.
It was rated an X-4.9 flare. X-class solar flares are the most intense, and 4.9 denotes significant intensity within the X-class. An X2 is twice as intense as an X1, an X3 is three times as intense, and so on, explains NASA.
Solar flares can affect GPS and other signals, though the radiation cannot pass through the Earth’s atmosphere to affect people. The U.S. National Weather Service reports that the Earth and the flare are not currently aligned in such a way that an impact is expected, but monitoring will continue.
Astronomer and Slate blogger Phil Plait describes solar flares well: “Huge magnetic energies stored in sunspots … [get] let loose all at once, creating an explosion that dwarfs all of humanity’s weapons combined.”