Astronomers scrutinized last year’s eclipse. Here’s what they’ve learned
New research is providing hints about what’s going on in the sun’s atmosphere
BY LISA GROSSMAN 11:53AM, MAY 29, 2018
LEESBURG, Va. — Astronomers watching the 2017 solar eclipse from the ground and from the air witnessed new, tantalizing features of the sun’s outer atmosphere.
Three teams have recently presented their first science results from the Great American Eclipse. Combined, the findings could help disentangle lingering solar puzzles, such as how bursts of plasma leave the sun, why the outer atmosphere, the solar corona, is so well organized and what is the nature of the corona’s magnetic field.
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. (That was one of four sites from which their team monitored the eclipse.) The team had used an earlier version of the instrument, which takes in specific wavelengths of light that can trace different coronal temperatures, to watch a solar eclipse in March 2015 from Svalbard, Norway.
NEW AND IMPROVED During the August 21 eclipse, scientists captured the first-ever infrared image of the corona, shown here in an unprocessed form.
NASA, SWRI, SOUTHERN RESEARCH
In 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. “We were very surprised,” Ding says. He thinks the cooler material may be trapped within plasma bubbles and can’t get out. “The stunning thing is that they survive.”
cont'd:The team also measured solar material’s Doppler shift, or the change in wavelength as the material moved toward or away from Earth. The shifts suggested that the scientists had caught a huge bubble of plasma erupting off the sun’s surface and fleeing out into space in 2015 (SN Online: 6/16/17). At the time, they thought seeing such an explosion, called a coronal mass ejection, was just luck.
If so, their luck held for the 2017 eclipse. The researchers haven’t finished processing all of their data yet, but preliminary results showed uncharged hydrogen and helium atoms fleeing the sun as far out as 3.5 solar radii from the edge of the sun’s bright disk, at speeds of about 600 kilometers per second.
https://www.sciencenews.org/article/ast ... se-results
Sorry for the repeat if this has already been covered.