A strange phenomenon on the sun captured by the solar spacecraft for the first time – the mystery has been solved

A magnetic phenomenon known as solar rebound has been imaged by the ESA/NASA Solar Orbiter for the first time. The image is enlarged on the switch (blue/white feature extending towards the left) as captured in the solar corona by the Metis instrument on March 25, 2022. The earlier switch appears to be related to the active region seen in the central ultraviolet imagery. image (right). Credit: ESA and NASA/Solar Orbiter/EUI & Metis Teams, D. Telloni et al. (2022)

With new data from the closest pass to the Sun so far, the European Space Agency /[{” attribute=””>NASA Solar Orbiter spacecraft has found compelling clues as to the origin of solar magnetic switchbacks. The discovery points toward how their physical formation mechanism might help accelerate the solar wind.

Solar Orbiter has made the first-ever remote sensing observation consistent with a magnetic phenomenon called a solar switchback – sudden and large deflections of the solar wind’s magnetic field. The new observation provides a full view of the structure, confirming it has an S-shaped character, as predicted. Moreover, the global perspective provided by the Solar Orbiter data indicates that these rapidly changing magnetic fields can have their origin near the surface of the Sun.

Shows a close-up of Solar Orbiter Metis data that has been turned into a Switch Evolution movie. The sequence represents about 33 minutes of data taken on March 25, 2022. The bright structure forms as it propagates from the Sun. When it reaches its full development, it bends back on itself and acquires the distorted S-shape characteristic of magnetic switching. The hull expands at 80 km/s but the entire hull is not moving that fast. Instead, it stretches and deforms. This is the first time that magnetic bounce has been observed at a distance. All other discoveries occurred when spacecraft flew through these turbulent magnetic regions. Credit: ESA and NASA/Solar Orbiter/Metis Teams; Tiloni et al. (2022)

Although a number of spacecraft have flown through these puzzling regions before, the in-situ data only allows measurements at one point and time. As a result, the structure and shape of the switch must be inferred[{” attribute=””>plasma and magnetic field properties measured at just one point.

When the German-US Helios 1 and 2 spacecraft flew close to the Sun in the mid-1970s, both probes recorded sudden reversals of the Sun’s magnetic field. These mysterious reversals were always abrupt and always temporary. They only lasted from a few seconds to a number of hours before the magnetic field switched back to its original direction.

These magnetic structures were also probed at much larger distances from the Sun by the Ulysses spacecraft in the late 1990s. Instead of a third of the Earth’s orbital radius from the Sun, where the Helios missions made their closest pass, Ulysses operated mostly beyond the Earth’s orbit.

How Solar Switchback Is Formed

How a solar switchback is formed infographic. Solar Orbiter has made the first ever remote sensing observation of a magnetic phenomenon called a solar ‘switchback’, proving their origin in the solar surface and pointing to a mechanism that might help accelerate the solar wind. Credit: ESA & NASA/Solar Orbiter/EUI & Metis Teams and D. Telloni et al. (2022); Zank et al. (2020)

Their number rose dramatically with the arrival of NASA’s Parker Solar Probe in 2018. This clearly indicated that the sudden magnetic field reversals are more numerous close to the Sun, and led to the suggestion that they were caused by S-shaped kinks in the magnetic field. This puzzling behavior earned the phenomenon the name of switchbacks. A number of ideas were proposed as to how these might form.

On March 25, 2022, Solar Orbiter was just a day away from a close pass of the Sun – bringing it within the orbit of planet Mercury – and its Metis instrument was taking data. Metis blocks out the bright glare of light from the Sun’s surface and takes pictures of the Sun’s outer atmosphere, known as the corona. The particles in the corona are electrically charged and follow the Sun’s magnetic field lines out into space. The electrically charged particles themselves are called a plasma.

Capturing a Solar Switchback

The Sun as seen by the ESA/NASA Solar Orbiter spacecraft on March 25, 2022, one day before its closest approach of about 0.32 au, which brought it inside the orbit of planet Mercury. The central image was taken by the Extreme Ultraviolet Imager (EUI) instrument. The outer image was taken by the coronagraph Metis, an instrument that blocks out the bright light of the Sun’s surface in order to see the Sun’s faint outer atmosphere, known as the corona. The Metis image has been processed to bring out structures in the corona. This revealed the switchback (the prominent white/light blue feature at the roughly 8 o’clock position in the lower left). It appears to trace back to the active region on the surface of the Sun, where loops of magnetism have broken through the Sun’s surface. Credit: ESA & NASA/Solar Orbiter/EUI & Metis Teams and D. Telloni et al. (2022)

At around 20:39 UT, Metis recorded an image of the solar corona that showed a distorted S-shaped kink in the coronal plasma. To Daniele Telloni, National Institute for Astrophysics – Astrophysical Observatory of Torino, Italy, it looked suspiciously like a solar switchback.

Comparing the Metis image, which had been taken in visible light, with a concurrent image taken by Solar Orbiter’s Extreme Ultraviolet Imager (EUI) instrument, he saw that the candidate switchback was taking place above an active region cataloged as AR 12972. Active regions are associated with sunspots and magnetic activity. Further analysis of the Metis data showed that the speed of the plasma above this region was very slow, as would be expected from an active region that has yet to release its stored energy.

Daniele instantly thought this resembled a generating mechanism for the switchbacks proposed by Prof. Gary Zank, from the University of Alabama in Huntsville, USA. The theory looked at the way different magnetic regions near the surface of the Sun interact with each other.

The European Space Agency (ESA) solar probe has solved the mystery of a magnetic phenomenon in the solar wind. It took the first-ever image of a “rebound” in the solar corona, confirming its expected “S”-shaped shape. Rebound is defined by rapid fluctuations in the direction of the magnetic field. The observed switch is related to an active region associated with sunspots and magnetic activity as there is an interaction between open and closed magnetic field lines. The interaction releases energy and sends an S-shaped turbulence into space. The new data suggests that switching processes can originate near the surface of the Sun, and may be important in understanding the acceleration and heating of the solar wind. Credit: ESA

Near the Sun, and especially above the active regions, there are open and closed magnetic field lines. The closed lines are magnetic rings that curve in the solar atmosphere before bending and disappearing again into the sun. Very little plasma can escape into space above these field lines, so the speed of the solar wind tends to be slow here. Open field lines are the opposite, they emanate from the Sun and connect to the solar system’s interplanetary magnetic field. They are magnetic highways along which plasma can flow freely, and they lead to fast solar winds.

Daniel and Gary demonstrated that switching processes occur when there is an interaction between the region of open field lines and the region of closed field lines. When field lines cluster together, they can reconnect in more stable configurations. Instead of breaking the whip, this releases energy and releases an S-shaped turbulence traveling into space, which a passing spacecraft will record as bouncing.

Create solar bounce

Metis’ observation of retrograde is consistent with the acoustic theoretical mechanism of producing solar magnetic switches proposed by Professor Gary Zanck in 2020. The main observation was that the reversal could be seen from the top of a solar active region. This sequence illustrates the chain of events that researchers believe occurs. (a) Active regions on the Sun can be characterized by open and closed magnetic field lines. Closed lines curve in the solar atmosphere before they curve back to the sun. Open field lines connect to the interplanetary magnetic field of the Solar System. (b) When an open magnetic region interacts with a closed region, the magnetic field lines can reconnect, creating an approximately S-shaped field line and producing a burst of energy. (c) When the field line responds to reconnect and release energy, an outward diffuse torsion is placed. This is the switch. A similar switch is also sent in the opposite direction, down the field line, and into the sun. Credit: Zank et al. (2020)

According to Gary Zank, who proposed one of the theories about the origin of transpositions, “The first image of Metis that Daniele Lee showed almost immediately suggested the cartoon we drew (see image above) in developing the mathematical model for recursion. Of course, the first image was just a snapshot, And we had to temper our excitement until we used Metis’ excellent coverage to extract temporal information and perform a more detailed spectroscopic analysis of the images themselves. The results proved to be absolutely stunning!”

Together with a team of other researchers, they built a computer model of the behavior, and found that their results bear a striking similarity to the Metis image, especially after they included calculations of how the structure elongated as it propagated outward through the solar corona. .

Danielle, whose findings were published in a research paper in Astrophysical Journal Letters.

In understanding switching processes, solar physicists may also take a step toward understanding the details of how the solar wind accelerates and heats away from the sun. This is because when spacecraft fly through the switch points, they often register a localized acceleration of the solar wind.

“The next step is to try to statistically correlate the shifts observed at the site with their source regions on the Sun,” Danielle says. In other words, to fly a spacecraft through the magnetic reversal and be able to see what happened on the surface of the Sun. This is exactly the kind of correlation science the Solar Orbiter is designed to do, but it doesn’t necessarily mean that the Solar Orbiter needs to fly through the switch. It could be another spacecraft, like the Parker Solar Probe. As long as the on-site and remote sensing data are in sync, Danielle can make the correlation.

“This is exactly the kind of result we were hoping for with the Solar Orbiter,” says Daniel Muller, ESA Solar Orbiter Project Scientist. “With each orbit, we get more data from our group of ten instruments. Based on results like these, we’ll fine-tune the planned observations of the Solar Orbiter’s upcoming solar encounter to understand how the Sun relates to the solar system’s broader magnetic environment. This was the first pass Solar Orbiter is very close to the Sun, so we expect more exciting results in the future.”

solar orbit The corridor near the sun – Once again inside Mercury’s orbit at a distance of 0.29 times the distance between the Earth and the Sun – it will take place on October 13. Earlier this month, on September 4, the Solar Orbiter made a gravity-assisted flyby of[{” attribute=””>Venus to adjust its orbit around the Sun; subsequent Venus flybys will start raising the inclination of the spacecraft’s orbit to access higher latitude – more polar – regions of the Sun.

Reference: “Observation of a Magnetic Switchback in the Solar Corona” by Daniele Telloni, Gary P. Zank, Marco Stangalini, Cooper Downs, Haoming Liang, Masaru Nakanotani, Vincenzo Andretta, Ester Antonucci, Luca Sorriso-Valvo, Laxman Adhikari, Lingling Zhao, Raffaele Marino, Roberto Susino, Catia Grimani, Michele Fabi, Raffaella D’Amicis, Denise Perrone, Roberto Bruno, Francesco Carbone, Salvatore Mancuso, Marco Romoli, Vania Da Deppo, Silvano Fineschi, Petr Heinzel, John D. Moses, Giampiero Naletto, Gianalfredo Nicolini, Daniele Spadaro, Luca Teriaca, Federica Frassati, Giovanna Jerse, Federico Landini, Maurizio Pancrazzi, Giuliana Russano, Clementina Sasso, Ruggero Biondo, Aleksandr Burtovoi, Giuseppe E. Capuano, Chiara Casini, Marta Casti, Paolo Chioetto, Yara De Leo, Marina Giarrusso, Alessandro Liberatore, David Berghmans, Frédéric Auchère, Regina Aznar Cuadrado, Lakshmi P. Chitta, Louise Harra, Emil Kraaikamp, David M. Long, Sudip Mandal, Susanna Parenti, Gabriel Pelouze, Hardi Peter, Luciano Rodriguez, Udo Schühle, Conrad Schwanitz, Phil J. Smith, Cis Verbeeck and Andrei N. Zhukov, 12 Septmeber 2022, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ac8104