A NASA satellite has spotted unexpected X- and C-shaped structures in Earth’s ionosphere, the layer of electrified gas in the planet’s atmosphere that allows radio signals to travel over long distances. The ionosphere is an electrified region of Earth's atmosphere that exists because radiation from the sun strikes the atmosphere. Its density increases during the day as its molecules become electrically charged. That's because sunlight causes electrons to break off of atoms and molecules, creating plasma that enables radio signals to travel over long distances. The ionosphere’s density then falls at night — and that's where GOLD comes in.