Solar Orbiter made the first remote sensing observation consistent with a solar change, providing a complete picture of the structure, confirming that it has an S-shaped character, as predicted. In addition, the global view offered by the data from the Solar Orbiter suggests that these rapidly changing magnetic fields may have their origin close to the Sun. Although many spacecraft have passed through these mysterious regions in the past, the in situ data only allow one measurement at a specific point and time. As a result, the structure and shape of the switching must be inferred from measurements of plasma properties and magnetic field recorded at a single location. Solar reversals were found to occur frequently after the launch of NASA’s Parker Solar Probe in 2018. This strongly suggests that rapid magnetic field reversals occur more regularly near the Sun and raises the possibility that magnetic field twists bring them into an S shape . Switchbacks is the name given to the phenomenon because of its complex behavior. As to how they could form, various theories have been put forward. A close-up of the Solar Orbiter Metis data turned into a movie shows the progress of the return. The sequence represents about 33 minutes of data taken on March 25, 2022. The bright structure forms while propagating outward from the Sun. As it reaches its full growth, it bends back on itself and takes on the distorted S-shape characteristic of a magnetic reentry. The structure is expanding at a speed of 80 km/s but the whole structure is not moving at this speed. Instead, it stretches and deforms. This is the first time a magnetic change has ever been observed from a distance. All other detections have been made when spacecraft have flown through these disturbing magnetic regions. Credits: ESA & NASA/Solar Orbiter/Metis Teams D. Telloni et al. (2022) On March 25, 2022, the Solar Orbiter was just one day away from a close pass of the Sun – bringing it into the orbit of the planet Mercury – and its Metis instrument was taking data. Metis blocks out the bright glow of light from the Sun’s surface and takes pictures of the corona. Around 20:39 UT, Metis captured an image of the solar corona that showed a distorted S-shaped bend in the coronal plasma. According to Daniele Telloni, National Institute of Astrophysics – Astrophysical Observatory of Turin, Italy – it must be a solar change. The image was later compared to an image taken by the Solar Orbiter’s Extreme Ultraviolet Imager (EUI) instrument. The candidate switching was found to occur over an active region attributed to AR 12972. Further analysis showed that the plasma velocity over this region was very slow, as would be expected from an active region that has not yet released its stored energy. Daniele recognized that this is similar to the switch generation mechanism presented by Professor Gary Zank of the University of Alabama in Huntsville, USA. The theory looked at the interactions between various magnetic regions near the Sun’s surface. Daniele and Gary demonstrated that switching occurs when there is an interaction between a region of open field lines and a region of closed field lines. As the field lines become crowded, they can be reconnected into more stable configurations. Rather like the cracking of a whip, this releases energy and creates an S-shaped disturbance that travels through space, which a passing spacecraft will record as a return. Gary Zank said, “The first image from Metis that Daniele showed me almost immediately suggested the animations we had designed to develop the mathematical model for a return. Of course, the first image was just a snapshot, and we had to temper our excitement until we could use the excellent Metis coverage to extract temporal information and do a more detailed spectral analysis of the images themselves. The results turned out to be spectacular!” The scientists also built a computer model of behavior. They found that their results bore a striking resemblance to the Metis picture, especially after including calculations of how the structure would elongate as it propagated outward through the solar corona. Daniele said, “I would say that this first image of a magnetic change in the solar corona revealed the mystery of their origin.” “The next step is to try to statistically link the transitions observed in situ to their source regions on the Sun. In other words, to fly a spacecraft through the magnetic reversal and be able to see what has happened on the solar surface. That’s exactly the kind of docking science the Solar Orbiter was designed to do, but it doesn’t necessarily mean the Solar Orbiter has to fly through the switch. It could be another spacecraft, like the Parker Solar Probe. As long as the in situ data and the remote sensing data are simultaneous, Daniele can perform the correlation.” Daniel Müller, ESA’s Solar Orbiter Project Scientist, said: “This is exactly the result we expected with Solar Orbiter. We get more data from our suite of ten instruments on every orbit. Based on results like this, we will optimize observations planned for Solar Orbiter’s next solar rendezvous to understand how the Sun is connected to the wider magnetic environment of the Solar System. This was Solar Orbiter’s first close pass of the Sun, so we expect many more exciting results to come.” Journal Reference:
