A team of scientists who collected numerous observations of last summer’s total solar eclipse via telescopes and electronic cameras has used the data to better understand motions within the solar corona, the Sun’s outer atmosphere.
Jay Pasachoff of Williams College in Williamstown, MA, who led the team in observing the eclipse in Salem, Oregon, presented their findings to the 232nd Meeting of the American Astronomical Society (AAS) in early June.
His team has observed numerous solar eclipses during various times in the 11-year sunspot cycle.
The Sun’s corona is visible only during the total phase of a solar eclipse, which lasted about two-and-a-half minutes on August 21, 2017.
“We could see giant streamers coming out of low solar latitudes as well as plumes out of the Sun’s north and south poles, all held in their beautiful shapes by the Sun’s magnetic field. In the months since the eclipse, we have used computers to pick out the best part of dozens of the images to make extremely high-contrast images that allow us to measure motions at extremely high speeds in the corona, as we compare our composite images with some made by coordinated colleagues 65 minutes farther east along the path of totality,” Pasachoff said.
Incredibly, motions within the solar corona attained speeds of several hundred miles per second during the eclipse.
Because the sunspot cycle is approaching solar minimum, when the Sun is least active, coronal streamers extending millions of miles into space were seen only in the Sun’s equatorial regions, he explained.
Thin gas plumes were seen extending both north and south of the Sun’s disk.
Although the solar corona is about one million times fainter than the rest of the Sun, it is also significantly hotter than the Sun’s surface for reasons scientists do not yet fully understand.
“Only at a total solar eclipse, when the blue sky goes away because normal sunlight is hidden by the Moon, can we see the corona at all this well,” Pasachoff explained. “And because the Sun’s magnetic field changes over the 11-year sunspot cycle and erratically as well, each time we look at the corona–even when we get only a couple of minutes to see it every couple of years somewhere in the world–we have a new Sun to study.”
A better understanding of the Sun’s influence on the Earth is crucial because solar activity can be harmful to satellites and cause both blackouts and power surges on the planet’s surface.