An article published in the journal “Physical Review Letters” reports the passage of NASA’s Parker Solar Probe through the Sun’s atmosphere, under what is called the Alfven critical surface. NASA announced this success, the first for an artificial vehicle, at the annual American Geophysical Union Meeting. It’s a milestone not only for this space probe’s mission but for the study of the Sun in general. Specifically, the Parker Solar Probe passed through what is known as the corona, the upper part of the atmosphere, collecting samples and measuring magnetic fields. The information gathered directly from the solar plasma will help to better understand the processes taking place in the star that, among other things, supports life on Earth and affects the environment on the Earth and the other objects in the solar system.
Despite the very broad observations of the Sun with telescopes and space probes, there are still various less-than-clear processes taking place within it. The Parker Solar Probe mission, launched on August 12, 2018, aims to provide answers thanks to a spacecraft capable of passing through the solar atmosphere.
On April 28, 2021, a spacecraft somehow touched the Sun for the first time after previously making seven flybys that never passed the Alfven critical surface, the point where gravity and magnetic fields are too weak to contain solar plasma. There were very rough estimates of where that point was, and the Parker Solar Probe spotted it about 13 million kilometers above the Sun’s surface.
A discovery concerning the Alfvén’s critical surface is that it’s not spherical but “wrinkled”. The data collected suggests that its irregularities are caused by magnetic structures called pseudostreamers, although the process that pushes the Alfven critical surface is unclear.
The passage of the Parker Solar Probe within the Sun’s atmosphere also made it possible to identify the origin of the solar switchbacks, zig-zag-shaped structures in the solar wind. The data shows a point where a switchback originates in the visible surface of the Sun, the photosphere. In 2019, the spacecraft had already sighted several solar switchbacks, indicating that they’re not rare but common in the solar wind.
Among the studies that can make the most of the Parker Solar Probe is that of the coronal streamers, considered the sources of the so-called slow solar wind. So far, they had only been seen from afar but have now been closely examined and photographed. The image (NASA/Johns Hopkins APL/Naval Research Laboratory) shows various views of coronal streamers: they’re the structures that are moving upward in the top row and angled downward in the bottom row.
These are some of the results obtained by the Parker Solar Probe, and it will now be possible to build upon them, as scientists know where to look for more information on solar phenomena. The data obtained and the data that will come in the future will help improve solar weather models. Among other things, that will help to understand processes that can also affect the Earth such as flares which, in severe cases, could cause a lot of damage to satellites and even to equipment on the surface.
