Five things we learned from last year’s Great American Eclipse

Credit: NASA

Temporary weather effects and more. For more background, there are several extra links in the original ScienceNews article.

A year after the total solar eclipse of 2017, scientists are still pondering the mysteries of the sun.

It’s been a year since the total solar eclipse of August 21, 2017, captured millions of imaginations as the moon briefly blotted out the sun and cast a shadow that crisscrossed the United States from Oregon to South Carolina.

“It was an epic event by all measures,” NASA astrophysicist Madhulika Guhathakurta told a meeting of the American Geophysical Union in New Orleans in December. One survey reports that 88 percent of adults in the United States — some 216 million people — viewed the eclipse either directly or electronically.

Among those were scientists and citizen scientists who turned their telescopes skyward to tackle some big scientific mysteries, solar and otherwise. Last year, Science News dove deep into the questions scientists hoped to answer using the eclipse. One year out, what have we learned?

1. The eclipse sent ripples through Earth’s atmosphere.

Normally, the sun’s radiation splits electrons from atoms in the atmosphere, forming a charged layer called the ionosphere, which stretches from 75 to 1,000 kilometers up. But when sunlight briefly disappears during an eclipse, the electrons rejoin their atoms, creating a disturbance in the ionosphere that is detectable with receivers on the ground (SN Online: 8/13/17).

The moon’s supersonic shadow produced a bow wave of atoms piling up in the ionosphere, similar to the wave at the prow of a boat, Shun-Rong Zhang of MIT’s Haystack Observatory in Westford, Mass., reported in December. Although such bow waves were predicted in the 1960s, this was the first time they were definitively observed.

The eclipse also sent a wave traveling through the thermosphere, an uncharged layer of the atmosphere about 250 kilometers high, that was observed from as far away as Brazil nearly an hour after the eclipse ended (SN: 5/26/18, p. 14). And measurements of temperature, wind speed and sunlight intensity showed that the eclipse briefly changed the weather along the path of darkness.

Continued here.