Signals from navigation satellites, radio broadcasts, and distant spacecraft all squeeze through a thin, electrified veil in Earth’s atmosphere called the ionosphere. Stretching from about 50 miles to nearly 400 miles up, this region bristles with charged particles set loose by daylight.
After sunset, that energy settles, but not always in the tidy pattern engineers expect. A new set of nighttime snapshots shows the plasma folding itself into unexpected letters of the alphabet – and that spelling lesson matters for everyone who relies on an accurate map or clear call.
Most evenings, two broad ribbons of extra-dense plasma form on either side of Earth’s magnetic equator. Together they make the Equatorial Ionization Anomaly, a feature first charted in the…