Solar eclipse project sheds new light on solar corona

A team led by Southwest Research Institute successfully conducted two land and airborne experiments to collect unique solar data from the April 8, 2024, total solar eclipse projected from Texas to Maine. The American Telescope Eclipse (CATE) 2024 experiment attracted more than 200 people. A broad, approachable and inclusive community of participants attempted to create a continuous 60-minute high-resolution film documenting this exciting event.

A survey conducted at about the same time used unique equipment mounted on a NASA WB-57F research aircraft to track the eclipse shadow so that it could only be observed from a bird’s eye view.

“The relative rarity of total solar eclipses provides scientists with a unique opportunity to study the hot atmosphere above the sun’s visible surface,” said Dr. Amir Kaspi, principal investigator of both projects. “But more importantly, through CATE 2024, the eclipse provides a connecting experience between scientists and communities along the way, sharing this incredible, awe-inspiring event. We want the public to be more interested in the sun and Its light generates new interest and appreciation.

Total solar eclipses allow scientists to observe complex and dynamic features of the Sun’s outer atmosphere in ways that would be impossible or impractical any other way, opening new windows into our understanding of the corona. The faint light from the corona is often masked by the intense brightness of the Sun itself, while certain wavelengths of light are blocked by Earth’s atmosphere.

CATE 2024 deployed a network of 35 community actors, or “citizen scientists,” representing local communities along the eclipse’s path, deploying a “bucket brigade” of small telescopes along the eclipse’s cross-country path. The scientific goals of CATE 2024 require measuring the polarization of light, or the direction of oscillating light waves, in the corona.

“You’re familiar with this because sometimes you wear sunglasses with polarizing filters on your face to filter out polarized light at certain angles,” Caspi said. “The Citizen CATE 2024 telescope’s sensor has pixels on each pixel. Both are equipped with polarizing filters that allow us to measure four different polarization angles throughout the corona, providing much more information than just measuring the brightness of the light.”

Caspi also led an aerial project to observe the solar corona from an altitude of 50,000 feet during a solar eclipse. These high-altitude observations both provide measurements that cannot be made from the ground and avoid any weather-related risks. Caspi’s team deployed a new set of sensitive, high-speed, visible and infrared imagers built by the SCIFLI team at NASA Langley Research Center and installed in the nose cone of the WB-57 jet.

Observing the corona’s complex motions through new wavelengths and new polarization measurements will help scientists understand why it is so hot. The temperature of the solar corona reaches millions of degrees Celsius, hundreds of times hotter than the temperature of the visible surface below, a strange paradox and a long-standing scientific mystery.

The corona is also one of the major sources of volcanic eruptions that trigger geomagnetic storms around Earth. These phenomena can damage satellites, cause power grid outages, and disrupt communications and GPS signals, so as the world becomes increasingly reliant on such systems, it’s important to better understand them.

“Combining airborne operational data with CATE 2024’s hour-long observations will provide a more complete picture of the Sun’s mysterious corona,” said SwRI co-investigator Dr. Dan Seaton, scientific lead for both projects.

“Both experiments required tremendous effort and precise timing to obtain the data we needed,” Caspi said. “I am honored and in awe of the talented team who collaborated so diligently. I can’t wait to delve deeper into our Collected data.”