"This is what we expect from some theories, and this pinpoints a source for the solar wind itself.The two main regions of the Sun's atmosphere as seen during an eclipse: corona (top) and chromosphere (bottom). "The structure of the regions with switchbacks matches up with a small magnetic funnel structure at the base of the corona," said astronomer Stuart Bale of the University of California, Berkeley, lead author on a paper on the phenomenon in press at The Astrophysical Journal. Now Parker has detected them inside the solar atmosphere, suggesting that at least some of the switchbacks come from the lower corona. Then on its sixth flyby, the probe's data showed us that switchbacks occur from patches. We've known about switchbacks since the 1990s, but it wasn't until Parker investigated them in 2019 that we learnt that they are rather common. These are Z-shaped kinks in the magnetic field of the solar wind, and it's not currently known where or how they form. Parker also investigated a phenomenon known as solar switchbacks.
![corona sun corona sun](https://i.redd.it/8gl2vdhvwzyz.jpg)
Particles no longer buffeted the spacecraft quite so chaotically, and the magnetic field was more orderly. Inside the pseudostreamer, conditions were quieter than the surrounding solar atmosphere. Parker's data suggest that these structures are responsible for the deformation of the Alfvén critical surface, although we don't currently know why. At lower depths, Parker encountered a magnetic structure known as a pseudostreamer, which we can see arcing out from the Sun during solar eclipses. Interestingly, the probe seemed to encounter the magnetic conditions of the corona sporadically, suggesting that the Alfvén critical surface is wrinkled. Parker entered the corona at 19.7 solar radii, dipping down to as low as 18.4 solar radii during its corona jaunt. Estimates had put the Alfvén critical surface at somewhere between 10 and 20 solar radii from the center of the Sun. One of the goals of Parker was to find out more about the Alfvén critical surface namely, where it is, and what its topography is like, since we didn't know either of those things. What we call the 'surface' of the Sun, composed of roiling convection cells plasma and known as the photosphere, is far below. Instead, its boundary is defined by what we call the Alfvén critical surface, where gravity and the Sun's magnetic fields are too weak to contain the solar plasma.Ībove this point, the solar wind emerges, blowing powerfully through the Solar System, so fast that waves within the wind break away from the Sun. These were imaged by the Parker probe during the ninth perihelion in August this year.
![corona sun corona sun](https://zone1-ibizaspotlightsl.netdna-ssl.com/sites/default/files/styles/generic_three_quarter_width/public/article-images/98998/embedded-1404756324.jpg)
(NASA/Johns Hopkins APL/Naval Research Laboratory)Ībove: The bright features visible in the pictures here are coronal streamers, normally only seen from Earth during an eclipse. We can actually see the spacecraft flying through coronal structures that can be observed during a total solar eclipse." "We see evidence of being in the corona in magnetic field data, solar wind data, and visually in images. "Flying so close to the Sun, Parker Solar Probe now senses conditions in the magnetically dominated layer of the solar atmosphere – the corona – that we never could before," said astrophysicist Nour Raouafi, Parker project scientist at the Johns Hopkins Applied Physics Laboratory. Previously, our estimates of these properties relied on external information. In its nearly five hours inside the solar atmosphere, Parker measured fluctuations in the Sun's magnetic field and sampled particles. The April perihelion was the eighth, and the first to actually enter the corona. In its planned seven-year mission, it should be making a total of 26 close approaches, or perihelions, to the Sun, using a total of seven gravity assist maneuvers from Venus to bring it ever closer. Parker Solar Probe launched in 2018, with its primary objective to probe the solar corona. "Not only does this milestone provide us with deeper insights into our Sun's evolution and its impacts on our Solar System, but everything we learn about our own star also teaches us more about stars in the rest of the Universe." "Parker Solar Probe 'touching the Sun' is a monumental moment for solar science and a truly remarkable feat," said astrophysicist Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters.