What the last eclipse taught us.

Science News looks back at last year’s dramatic solar eclipse and shows us why it was a big deal research-wise, too:

While thousands of eclipse watchers gathered across the country last August armed with special glasses and cameras, solar physicists Adalbert Ding and Shadia Habbal and their colleagues set up a specially designed spectrometer in Mitchell, Ore.

n both 2015 and 2017, the scientists observed evidence of relatively cool blobs of gas embedded in hot plasma in the outer corona. (The sun’s surface simmers at about 6000° Celsius, but its corona roasts at millions of degrees — and no one knows why.) Ding, of the Institute for Optics and Atomic Physics in Berlin, and Habbal, of the University of Hawaii in Honolulu, measured wavelengths of light emitted by atoms and charged particles called ions in the corona, as a proxy for the plasma’s heat.
To the researchers’ astonishment, they saw blobs of plasma during both eclipses that had maintained temperatures as low as 20,000° C embedded within material in the corona that was as hot as 3.7 million degrees Celsius, Ding said at the Triennial Earth-Sun Summit on May 23.

In another talk at the meeting, solar physicist Amir Caspi of the Southwest Research Institute in Boulder, Colo., presented results from a different vantage point: a WB-57F aircraft flying at about 15 kilometers in altitude.

Caspi’s team was trying to see signs of magnetic waves called Alfvén waves rippling through the outer corona. Simulations of the plasma in the corona “lead you to this Velcro-looking thing, a tangled snarled mess,” Caspi said. “In fact, that’s not what we see.” Alfvén waves could smooth out the snarls, which could help explain why the material there is so neatly organized…. What’s more, the waves may contribute to the mysterious coronal heating.

n another experiment, solar physicist Jenna Samra of Harvard University and her colleagues were on the lookout for certain infrared wavelengths in the corona that were expected to be bright enough to see from the ground.

The team measured five wavelengths, one of which had never been seen before, the team reports in the April 1 Astrophysical Journal Letters.

Some pretty cool pictures at the link.