Because of atmospheric padding, the burst poses little risk to people on the ground. However, airplanes at cruising altitude and spacecraft are much more vulnerable. The flash also can zap electronics on satellites, which lie entirely outside the safety of Earth’s atmosphere.
While this initial burst can be dangerous, there’s a much slower wave of energy – a coronal mass ejection (CME) – that really can mess with electronics.
Not every flare produces a CME, and they often occur when no flare is present. When they do spew out, CMEs send strong waves of electromagnetic force our way. The most visible signs of this are the colorful northern and southern lights. But it also has more serious consequences.
For one, it can cause electrical transformers to trip or fail, which can lead to widespread power outages. A particularly powerful CME storm hit Earth in 1921, before electricity played as big a role in daily life. If a burst of similar magnitude hit today, it would interrupt power for as many as 130 million people, according to a recent report by the National Academy of Sciences. In 1989, a geomagnetic storm knocked out power to 6 million people in Quebec.
CMEs also can cause the Earth’s atmosphere to expand temporarily. This can cause low-orbit satellites, such as the constellation of Global Positioning System markers used for navigation, to drag in the denser air. Combined with changes in the transmission of radio waves caused by CMEs, this can lead to errors in positioning. The magnetic field also can induce glitches or even damage satellites.
Ron Mahmot, who manages the Satellite Operations Control Center for the National Oceanographic and Atmospheric Administration (NOAA), isn’t particularly concerned about potential damage from solar activity. NOAA has had only one satellite damaged by a solar flare. The 1994 incident merely shortened the life of the orbital weather-watcher; it did not totally disable it. And for the most critical NOAA satellites, those that monitor the United States from geosynchronous orbit, there is an on-orbit spare in place, with another that was due to launch at the end of April, and yet another already in production.