Web-like plasma structures have been found in the middle corona of the Sun by a group of scientists from the Southwest Research Institute (SwRI), NASA, and the Max Planck Institute for Solar System Research (MPS).
The scientists used a ground-breaking novel observing technique by imaging the middle corona in the ultraviolet (UV) spectrum.
Middle Solar Corona
With the Large Angle and Spectrometric Coronagraph (LASCO) mounted on the NASA and European Space Agency Solar and Heliospheric Observatory (SOHO) spacecraft, the US National Oceanic and Atmospheric Administration has been observing the Sun's corona since 1995 to track space weather that may have an impact on Earth.
However, LASCO has an observational gap that prevents scientists from seeing the middle solar corona, which is where the solar wind is generated.
Since the 1950s, the solar wind's outflow has been studied. According to Dr. Dan Seaton, a principal scientist at SwRI and one of the study's authors, solar wind changes may cause space weather and have an impact on satellites, electrical grids, and astronauts.
"The origins of the solar wind itself and its structure remain somewhat mysterious. While we have a basic understanding of processes, we haven't had observations like these before, so we had to work with a gap in information," Seaton said in a press release statement.
Solar Ultraviolet Imager
Seaton proposed using a different instrument, the Solar Ultraviolet Imager (SUVI) on NOAA's Geostationary Operational Environmental Satellites (GOES), at either side of the Sun rather than directly at it and performing UV assessments for a month to discover novel ways of observing the Sun's corona.
In the central corona of the Sun, Seaton and his associates observed extended, web-like plasma formations. Particles are propelled into space by interactions within these structures, which release stored magnetic energy.
Nobody had ever kept track of what the Sun's corona is like in UV at this height for so long. According to Seaton, the research team was unsure if it would be successful.
But now, they have high-quality observations that fully integrate other observations of the Sun and heliosphere as a unified system for the first time.
Seaton reckons that observations could result in more thorough understandings and even more fascinating findings, such as projects like PUNCH (Polarimeter to Unify the Corona and Heliosphere), a SwRI-led NASA probe that will photograph how the Sun's outer corona becomes the solar wind.
With the ability to scan the Sun's middle corona, researchers can better understand how the solar wind engages with the rest of the solar system and link what PUNCH observes to its source.
Seaton notes that few people thought they could view the middle corona in UV at these distances before these new findings. He adds that these investigations have made it possible to view the corona in a completely new way.
The findings of the study were published in the journal Nature.
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