Solar flares are sudden, powerful releases of energy from the Sun’s surface, caused by the reconfiguration of its complex magnetic field. The event releases energy equivalent to millions of hydrogen bombs in a matter of seconds to an hour.
Most of the flare’s energy is emitted as electromagnetic radiation—radio waves, ultraviolet, visible light, infrared, microwaves, X‑rays, and gamma rays. Because electromagnetic waves travel at the speed of light (≈300,000 km/s), the radiation from a flare reaches Earth in roughly 500 seconds, or a little over eight minutes after it leaves the Sun.
Alongside the light, flares eject high‑energy particles. The fastest particles can arrive within about two minutes of the initial radiation, while larger eruptions known as coronal mass ejections (CMEs) travel at a fraction of the speed of light and can take three to four days to arrive at Earth.
Earth’s atmosphere and magnetic field shield us from the majority of a flare’s harmful effects. However, high‑latitude regions are more vulnerable. A notable example occurred in 1989 when a solar flare caused a nine‑hour power outage for 6 million Canadians in Quebec. Recent studies, such as Oak Ridge National Laboratory’s 2010 report on “Electromagnetic Pulse: Effects on the U.S. Power Grid,” warn that a powerful magnetic storm could severely damage the national grid. A 2011 NARUC report estimates a 50 percent chance of a catastrophic flare within several decades, underscoring the need for grid hardening and preparedness.
