The formations that Parker saw when she first approached the Sun are sudden reversals in the Sun's magnetic field in those regions. New information has now been added about their nature and effects on sunspots
The Sun's corona-like atmosphere can be 200 times hotter than the Sun's surface, even though it is further away from the ultimate heat source in the Sun's core. How the corona's heat seemingly defies physics has baffled scientists for decades, but it allows the sun's hot soup of charged particles, the plasma, to move fast enough to escape the sun's gravity and envelop our solar system in the form of the solar wind.
To solve the mystery, NASA built the Parker Solar Probe to dive into the corona and find its heat source. The spacecraft is equipped with instruments to directly measure the density, temperature and flow of the coronal plasma.
When it first approached the Sun, the probe detected hundreds of S-shaped bands in the Sun's magnetic field - called switchbacks because they briefly reverse the direction of the magnetic field - along with thousands of shallower bands. To some scientists, the revolutions appeared to be promising heat sources of the corona and the solar wind. Their severe S-shaped bend stored a lot of magnetic energy, which was likely released into the surrounding plasma as the rotors moved through space and eventually aligned.
"This energy has to go somewhere, and it is possible that it contributes to the heating of the corona and the acceleration of the solar winds," said Mujtaba Ahban-Tafti, a corresponding author of the study.
But to heat the corona, inversions have to pass through it, so it is essential to know where inversions form to understand their effect on the temperature of the corona. After digging into data from Parker's first 14 orbits around the Sun, the research team found that the S-shaped bands are common in the solar wind close to the Sun, but not within the corona.
Scientists still can't agree on what causes revolutions. Some believe that a vortex in the solar wind beyond the corona bends the magnetic field. Others think that upheavals begin their journey in front of the Sun, as magnetic lines and loops rapidly stir and collide and coalesce into bent shapes.
The results of the study rule out the latter hypothesis. If eddies were created by magnetic fields colliding with the face of the Sun, they should be even more common within the corona. But Achban-Tefti thinks that magnetic collisions can still play an indirect role in the origin of the inversions and the heating of the corona.
"Our theory can fill the gap between the two schools of thought regarding the creation mechanisms of S-shaped transformers," he said. "They must be formed outside the corona, but there can be a triggering mechanism inside it that causes upheavals to form in the solar wind."
When magnetic fields collide in front of the Sun, they vibrate like plucked guitar strings and send waves along the magnetic field into space. At the same time, the energy from the collisions creates very fast plasma currents in the solar wind.
Achban-Tefti thinks that the hot plasma distorts the plasma waves into inversions in the solar wind. If some of these waves are dispersed within the solar atmosphere before becoming inverted, they too can contribute to heating the corona.
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