On May 13, 2025 and May 14, 2025, the sun fired solar flares, and the radiation of those flares triggered radio black outs in some parts of the world, according to a forecast discussion from the National Oceanic Atmospheric Association (NOAA).

Solar flares — sudden, intense bursts of radiation — are the result of the sun releasing energy pent-up magnetic energy. Sunspots, which are concentrated areas of such energy, are often the source of many flares.

Although fascinating for astronomers to observe, they can also affect life on Earth and in space. The sudden burst of magnetic energy can interrupt radio signals on the side of the planet facing the flare. They can also interfere with navigation signals — even potentially disrupting spacecraft.

Solar Flare Strength Ratings

There strength is measured by letters, with X being the strongest class. Each subsequent letter after X denotes a 10-fold order of magnitude. The number following the letter indicates a more detailed level of strength within that category.

The strongest May 14, 2025 flare was classified as an X2.7, with two moderate ones also occurring that day. NOAA predicts that a series of moderate to strong flares will occur over the next week, with a 65 percent chance of M-Class (minor to moderate), and a 30 percent of another X-Class event.

Read More: Solar Flares are Stunning but are They Dangerous? Here’s What to Know

Coronal Mass Ejection

Wednesday’s X2.7 flare was accompanied by a coronal mass ejection (CME), an explosion of charged solar plasma often thrown from the sun’s surface simultaneously as the flare. Since flares travel at the speed of light, we see them within about eight minutes. CMEs travel much slower, so we might need to wait a few days after the accompanying flare to see them.

When a CME finally does reach Earth, its charge can trigger a geomagnetic storm that can manifest as northern or southern lights. CMEs can also take down power grids, and interfere with satellites and GPS systems. Like solar flares, they have their own classification system for strength, with G1 being the weakest and G5 representing the strongest.

Read More: The Strongest Solar Storm in History Impacted Earth 14,300 Years Ago

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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.