NASA spots unexpected X-shaped structures in Earth's upper atmosphere — and scientists are struggling to explain them

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.

NASA's Global-scale Observations of the Limb and Disk (GOLD) mission is a geostationary satellite that has been measuring densities and temperatures in Earth's ionosphere since its launch in October 2018. From its geostationary orbit above the western hemisphere, GOLD was recently studying two dense crests of particles in the ionosphere, located north and south of the equator. As night falls, low-density bubbles appear within these crests that can interfere with radio and GPS signals. However, it's not just the wax and wane of sunshine that affects the ionosphere — the atmospheric layer is also sensitive to solar storms and huge volcanic eruptions, after which the crests can merge to form an X shape.

In its new observations, GOLD found some of these familiar X shapes in the ionosphere — even though there weren't any kinds of solar or volcanic disturbances to create them.

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"Earlier reports of merging were only during geomagnetically disturbed conditions," Fazlul Laskar, a research scientist at the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP), said in a statement. Laskar is the lead author of a paper published in April in the Journal of Geophysical Research: Space Physics that described these unexpected observations. 

"It is an unexpected feature during geomagnetic quiet conditions," he said.