The Great American Eclipse Created a Giant Wave in Earth's Atmosphere

Brian Harding drove south to St. Louis last August to watch the total solar eclipse, but he didn't stay long after the spectacle. "As soon as it was over, I drove back to the city and opened up my computer and was making sure the instrument was taking data and everything," he told Newsweek.

That's because Harding, an engineer at the University of Illinois at Urbana-Champaign who focuses on space science, had organized an experiment to run during the eclipse's aftermath. He was hunting for elusive evidence of a long hypothesized atmospheric phenomenon, a giant wave traveling thousands of miles triggered by the abrupt night of the eclipse. As he and his colleagues report in a new paper published in the journal Geophysical Research Letters, the observations were successful, finally backing up decades of scientific suspicion.

Harding had to check the instrument from his computer because the wave was hundreds of miles south of where the eclipse passed overhead. He and his colleagues were exploring the distant ripples felt in Brazil as the atmosphere adjusted to the event's aftermath.

Read more: The August Solar Eclipse Left Fascinating Clues About Hidden Atmospheres and Vital Satellites

This is the second type of atmospheric wave scientists have identified using data from the August eclipse. The first, a new phenomenon dubbed a bow wave, is a medium-scale ripple among charged particles found in the atmosphere as the Moon blocks and then clears the sun.

What Harding was looking for instead was traces of much larger waves within the atmosphere itself, marked by wind-like movement of uncharged particles. As the Moon's shadow abruptly cools the atmosphere it passes above, that cool patch triggers a flow of atmospheric particles toward its center, sort of the reverse of a boat's wake.

"There are many sources that can trigger unusual disturbances," Shunrong Zhang, a space scientist at MIT's Haystack Observatory, who wasn't involved with the new study but who led the research on bow waves published in December, told Newsweek. "Now we find that the solar eclipse is an additional source."

Zhang said scientists were still working on understanding the details of how the atmosphere and its disturbances work. Under certain circumstances, those disturbances can affect communication technology like GPS.

Finding the eclipse wave came about thanks to some good luck. In early 2017, Harding visited a colleague who had been modeling predictions for how the eclipse would affect the atmosphere, and he realized he had access to just the sort of device that could gather data to support or undermine those predictions.

The August 21, 2017 solar eclipse, as seen from Madras, Oregon. Aubrey Gemignani/NASA via Getty Images

"What I noticed was that we had an instrument that was right where it needed to be to make the measurement," Harding said. The instrument needed some maintenance, but the team was able to get it up and running the day before the eclipse. "It's one of those times that science just works right," he said.

The team's measurements spotted the echoes of the initial wave even hours after the phenomenon began and thousands of miles away from its source. "Although it was a local phenomenon, it had global effects in the upper atmosphere," Harding said.

Because the team's observations matched the predictions made beforehand, the study suggests that scientists have a pretty good handle on how the atmosphere works, Harding said.