Thanks to data obtained from its closest passage to the Sun, the spacecraft solar orbiter from the European Space Agency (ESA) and NASA found compelling clues about the origin of the come back or magnetic ‘lashes’ and points out how its formation mechanism can contribute to accelerating the solar wind.
This probe made the first remote sensing or sensing compatible with one of these zigzags solar wind, i.e. large and sudden deviations of the solar wind’s magnetic field that cause it to bend in on itself.
The new observation provides a complete view of the structure, confirming that it s shape, as had been predicted. Furthermore, the information obtained indicates that these rapidly changing magnetic fields may have their origin close to the surface of the Sun.
Although several spacecraft have flown over regions where they have been observed before, the data on site they only allow a measurement at a single point and time. Consequently, the structure and shape of the change in direction must be inferred from the properties of the plasma and the magnetic field measured at that point.
When the German-American spacecraft Helios 1 and 2 flew close to the Sun in the mid-1970s, both recorded sudden reversals of the Sun’s magnetic field. These mysterious reversals were always sudden and temporary, lasting from a few seconds to several hours before the magnetic field returns to its original direction.
At the end of the 1990s, the spaceship ulysses also studied these magnetic structures at much greater distances from our star. Instead of a third of Earth’s orbital radius from the Sun, where the Helios missions made their closest pass, Ulysses mainly operated beyond Earth’s orbit.
Their number increased dramatically with the arrival of the probe. Sun Parker by NASA in 2018. This clearly indicated that these sudden ‘whips’ of the magnetic field are more numerous near the Sun and led to the suggestion that they were caused by S-shaped bends in the magnetic field. This disconcerting behavior has given the phenomenon the name of zigzags (English zigzag curves, like a road in a mountain pass). Various ideas have been proposed as to how they could be formed.
Diagram of the formation of a solar ‘whip’. / ESA & NASA/Solar Orbiter/EUI & Metis Teams and D. Telloni et al. (2022); Zank et al. (2020)
O March 25, 2022the Solar Orbiter probe was a day away from passing close to the Sun (it placed it in the orbit of the planet Mercury) and its impure instrument I was taking data. This device blocks the glare of light from the Sun’s surface and takes pictures of the Sun’s outer atmosphere, known as crown. Particles in this zone are electrically charged and follow the Sun’s magnetic field lines into space. Electrically charged particles are called plasma.
That day, Metis recorded an image of the Sun’s corona showing a distorted S-shaped fold in the coronal plasma. Per Daniele Tellonifrom the Instituto Nacional de Astrofísica – Astrophysical Observatory of Turin (Italy), looked suspicious come back solar.
Sum of Metis and EUI instruments
Comparing the Metis image, which had been taken in visible light, with a simultaneous image taken by the instrument Extreme Ultraviolet Imager (EUI) from Solar Orbiter, he saw that the candidate’s address change took place over a period of active region listed as AR 12972.
Active regions are associated with the sunspots and magnetic activity. Further analysis of the Metis data showed that the velocity of the plasma above this region was very slow, as would be expected from an active region that has not yet released its stored energy.
Daniele instantly thought that this resembled a recoil generating mechanism proposed by the professor. Gary Zank, from the University of Alabama at Huntsville (USA). His theory looked at how different magnetic regions near the Sun’s surface interact with each other.
Close to the Sun, and especially above the active regions, there are magnetic field lines open and closed. The lines closed they are loops of magnetism that project into the solar atmosphere before bending over and disappearing back into the Sun. Above them there is very little plasma that can escape into space, so the speed of the solar wind tends to be slow at this point. .
field lines Open they are the opposite, they emanate from the Sun and connect with the interplanetary magnetic field of the solar system. These are magnetic roads along which plasma can flow freely, giving rise to the fast solar wind.
Creation of a solar ‘switchback’. /Zank et al. (2020)
Daniele and Gary showed that zigzags occur when there is an interaction between a region of open field lines and a region of closed field lines. When field lines get crowded, they can reconnect in more stable configurations.
Like a whip, this releases energy and causes an S-shaped disturbance to travel into space, which a passing spacecraft will register as a zigzag.
According to Gary Zank, who proposed one of the theories about the origin of these solar ‘lashes’, “the first image of Metis that Daniele showed almost immediately suggested to me the caricatures we had drawn when developing the mathematical model of a come back. Of course, the first image was just a snapshot and we had to hold back our excitement until we used Metis’ excellent coverage to extract temporal information and do a more detailed spectral analysis of the images themselves. The results were absolutely spectacular.”
Confirmation with a computer model
Together with a team of other researchers, they built a computer model of the phenomenon, finding that their results bore a striking resemblance to the Metis image, especially after including calculations of how the structure would elongate during its propagation out of the solar corona. .
“I would say that this first image of a come back magnetic field in the solar corona has revealed the mystery of its origin”, says Daniele Telloni, whose results are published in an article in The Astrophysical Journal Letters.
By understanding the zigzags, solar physicists may also be taking a step closer to understanding the details of how the solar wind accelerates and heats away from the Sun. That’s because when spacecraft fly through switchbacks, they typically register a localized acceleration of the solar wind.
This first image of a magnetic ‘whip’ in the solar corona has revealed the mystery of its origin, and the next step is to try to statistically relate the zigzags observed in situ to their regions of origin on the Sun.
“The next step is to try to statistically relate the observed zigzags on site with their regions of origin on the Sun”, says Daniele. 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 scientific connection for which the Solar Orbiter was designed, but that doesn’t necessarily mean the Solar Orbiter has to fly through magnetic reversal. It could be another spacecraft, like the Parker Solar Probe. As long as the in situ and remote sensing data are simultaneous, Daniele can perform the correlation .
“This is exactly the kind of result we were hoping for with the Solar Orbiter,” says Daniel Müller, ESA’s project scientist for the Solar Orbiter. “With each orbit, we get more data from our suite of ten instruments. Based on results like this, we will refine observations planned for Solar Orbiter’s next solar encounter to understand how the Sun connects with the magnetic environment.” Solar System. This was the Solar Orbiter’s first approach to the Sun, so we’re looking forward to many more exciting results.”
The Solar Orbiter’s next approach to the Sun – again within the orbit of Mercury at a distance of 0.29 times the Earth-Sun distance – will take place on October 13. Earlier this month, on September 4, Solar Orbiter performed a gravity-assisted flyby of Venus to adjust its orbit around the Sun; Subsequent flybys of Venus will begin to increase the inclination of the spacecraft’s orbit to access higher latitude – more polar – regions of the Sun.
Spain review
“The consequences of mission design as solar orbiterin which, in an unprecedented way, ten instruments are combined —six for remote sensing and four for local measurement— aboard a spacecraft that approaches the Sun the closest to the planet Mercury (0.3 astronomical units) are produced regularly and today know one of the most spectacular results”, explained the researcher Jose Carlos Del Toro from the Institute of Astrophysics of Andalusia (IAA-CSIC) to SMC Spain.
“This is the direct identification through the instrument uncleanwith the help of the instrument EUIof one of the phenomena that has aroused great interest recently in the solar corona and in the origins of the solar wind”, he adds.
“The Parker Solar Probe’s formidable approach in 2018 showed that the appearance of these S-shaped structures is more common than expected, but no one has observed them directly,” concludes del Toro, co-principal investigator for the SO instrument. . /PHI aboard the Solar Orbiter.
Reference:
D. Telloni et al. “Observation of a magnetic switchback in the solar corona”. The Astrophysical Journal Letters2022