NASA’s IRIS Probe Spots Plasma Bombs and Nanoflares on Sun

The first results from a new NASA sun-studying spacecraft are in, and they reveal a complex and intriguing picture of Earth's star.

NASA's Interface Region Imaging Spectrograph probe, or IRIS, has observed "bombs" of plasma on the sun, nanoflares that rapidly accelerate particles, and powerful jets that may drive the solar wind, among other phenomena. The IRIS mission's insights are reported in five papers and a commentary published Thursday by the journal Science.

While spacecraft can enter planetary atmospheres, they cannot fly through the outer atmosphere of the sun, where temperatures reach 3.5 million degrees Fahrenheit (2 million degrees Celsius). Probes like IRIS instead must study the star from a safe distance. Unlike previous instruments, IRIS can take far more detailed observations of the sun, capturing observations of regions only 150 miles (240 kilometers) wide on a time scale of just a few seconds. [See images from IRIS]

"The combination of enhanced spatial and spectral resolution, [which are] both three to four times better than previous instruments, allows a much closer look [at the sun's atmosphere]," Hardi Peter of the Max Planck Institute for Solar System Research in Germany told by email. Peter was the lead author on the study of hot plasma "bombs."

The sun converts a huge amount of its magnetic energy into thermal energy, heating pockets of plasma. According to Peter, the amount of energy released would be enough to provide electric power to Germany for 8,000 years. The plasma is heated up to 180,000 degrees F (100,000 degrees C) in the middle of cooler surface regions.

These pockets explode like bombs, ejecting the superheated plasma. The upward-moving plasma probably disperses into the hot corona, Peter said, while the downward-moving plasma cools back down.

Another solar phenomenon has to do with the magnetic loops that rise up from the sun's surface into the upper atmosphere and snap apart. Paola Testa of the Harvard-Smithsonian Center for Astrophysics led a team that used IRIS to study the footprints of magnetic loops. He and his colleagues he found that the intensity changed over a span of 20 to 60 seconds.

Investigating possible causes, Testa determined that the variations were consistent with simulations of electrons generated from coronal nanoflares. "Nanoflares are short heating events releasing amounts of energy about a billion times smaller than large flares," Testa said.

— Nola Taylor Redd,

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