Parker Solar Probe approaches corona

Nasa spacecraft does hokey cokey in and out of the Sun

Image credit: Nasa

A Nasa spacecraft, the Parker Solar Probe, has finally 'touched' a the Sun, plunging itself into the previously unexplored upper solar atmosphere, the corona.

The Parker Space Probe was launched in 2018 with the intent of observing the Sun more closely than any other spacecraft.

The boundary between solar atmosphere and outgoing solar wind is known as the Alfvén critical surface. Researchers aimed to discover where this surface lay, using data collected by the spacecraft. In April, during its eighth close approach to the Sun, the probe encountered the tell-tale magnetic and particle conditions that marked this surface, 8.1 million miles from the centre of the Sun. However, it has taken several months to return the data and confirm the encounter. The plunge was announced this week during a meeting of the American Geophysical Union.

“Parker Solar Probe 'touching the Sun' is a monumental moment for solar science and a truly remarkable feat,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at Nasa’s Washington headquarters. “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.”

Data show it dipped in and out of the corona at least three times, each with a smooth transition. Preliminary data suggest the Parker spacecraft also dipped into the corona during its ninth close approach, although further analysis is required. It made its tenth close approach in November and will continue to draw closer to the centre of the Sun until its 'grand finale' orbit in 2025.

Professor Justin Kasper of the University of Michigan, an expert in solar physics, said: “The first and most dramatic time we were below for about five hours […] now, you might think five hours, that doesn’t sound big.” He explained that the spacecraft was moving so quickly during this time that it covered around 100km every second.

Data collected by Parker Solar Probe has already led to exciting observations and discoveries. They demonstrate the Alfvén critical surface is not smooth, but marked with spikes and valleys. Understanding how these 'wrinkles' are connected with solar activity could help scientists better understand solar activity that can affect life on Earth. At one point, the spacecraft logged a feature called a 'pseudostreamer': a massive structure that rises so far above the solar surface that they can be seen from Earth during solar eclipses.

Dr Nour Raouafi of John Hopkins University, who led the project, said: “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. We see evidence of being in the corona in magnetic field data, solar wind data, and visually in images. We can actually see the spacecraft flying through coronal structures that can be observed during a total solar eclipse.”

According to Raouafi, the corona was dustier than expected. Future coronal encounters will help scientists better comprehend the origin of solar wind, he said, and how it is heated and thrust out into space.

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