A hundred earths strung together side to side can fit across the diameter of the Sun: that’s how big it is. And very powerful, magnetically: the 11,000°F temperatures cross magnetic lines all the time, spawning “sunspot” solar storms that easily rival the Earth in size and send waves of electromagnetic radiation outwards. For our species, increasingly dependent in electrical equipment, these storms are always a source of trouble.

On this day, July 14, in 2000, one such storm resulted in one of the largest solar flares on record, sending waves of particles towards Earth. Ordinarily our planet’s outer magnetic layer would stop the particles above the atmosphere, but in this case the flood was overwhelming, and some of the particles got into the atmosphere.

The National Weather Center, which also monitors the magnetic conditions in the atmosphere, classified the resulting storm as a “strong,” a level 3 of 5 — not enough to cause any upsets in earthbound electronics, but enough to fry any unshielded components of satellites, and interfere with their recording and radio transmission.