For decades, scientists have puzzled over why the Sun’s outer atmosphere (the corona) warms the farther it moves from the Sun’s surface.
Now, thanks to data collected by NASA’s Parker Solar Probe, the long list of possible explanations has been shortened by one. The Parker Solar Probe is the fastest man-made object and has repeatedly grazed the Sun in search of clues to solving the so-called “coronal heating puzzle.”
During the investigation first contact with the sunits instruments recorded abrupt reversals of the Sun’s magnetic fields. Scientists call such occurrences “serpentines” and suspect that they play a role in heating the corona, primarily by releasing the magnetic energy stored in them as they move within the Sun. The sun and in space.
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“This energy has to go somewhere and could help heat up the corona and accelerate the solar wind,” said study co-author Mojtaba Akhavan-Tafti of the University of Michigan in a opinion.
The mystery of corona heating relates to the fact that the Sun’s outer atmosphere, the corona, is hundreds of times hotter than its “surface,” the photosphere. This is despite the fact that the photosphere is millions of kilometers closer to the Sun’s core, where the nuclear fusion that provides heat and energy to our star takes place.
Although the photosphere is cooler than the corona, it is responsible for most of the sunlight and completely “washes out” the light from the sun’s atmosphere. Therefore, the solar corona can only be seen when the light from the photosphere is blocked by a solar eclipse or by using a special instrument called a coronagraph.
This means that the Parker Solar Probe will have to brave temperatures of around 2,500 degrees Fahrenheit (about 1,400 degrees Celsius) to get as close to the sun as possible to study the corona.
Akhavan-Tafti and his team combed through data Parker collected from more than a dozen orbits around our star to figure out exactly where the switchbacks began, which is crucial to understanding their influence on the corona.
However, the features they were looking for could not be found anywhere, at least not within the corona. Instead, the probe’s data showed that serpentines in the solar wind are common near the Sun.
The finding suggests that the serpentines that heat the corona probably do not start at the Sun’s surface, ruling out one of the two leading hypotheses about the origin of the serpentines.
Scientists believe there may still be a trigger mechanism that heats the outermost parts of the sun. One such mechanism could be explosive collisions of chaotic magnetic field lines on the sun’s surface, Akhavan-Tafti said.
In such collisions, the magnetic fields vibrate like plucked guitar strings, accelerating the plasma in the solar wind to high speeds. This could distort magnetic waves near the Sun into serpentine lines. However, if some of these waves lose power before they leave the Sun, their energy would be released in the upper layers and would heat up the corona.
“The mechanisms that lead to the formation of the serpentines, and the serpentines themselves, could heat both the corona and the solar wind,” Akhavan-Tafti said in the press release.
This research refines our understanding of how the Sun works and may ultimately help scientists predict, detect, and prepare for solar storms.
This research represents the latest result to emerge from NASA’s Parker mission since it began in 2018.
Last month, the Parker Solar Probe completed its 20th approach to the sun, coming within 8 million kilometers of its surface, the Johns Hopkins Applied Physics Laboratory, which operates the spacecraft, said in a recently released opinion.
The probe has now flown outward, but will return the same distance on September 30 and will fly a million miles further from the sun on Christmas Eve this year. Scientists hope that data from these trips will reveal more about why the million-degree corona is the way it is.
The team’s research was published in The Astrophysical Journal Letters on July 29.
