Using United States NASA and ESA spacecraft, the researchers revealed how magnetic rotation near the Sun provides energy to the solar wind, affecting Earth and potentially affecting the habitability of exoplanets. This breakthrough helps answer long-standing questions about solar wind dynamics and has broader implications for understanding stellar phenomena across the Milky Way.
This artist's concept art shows a gyration or large kink in the sun's magnetic field. Image credit: United States NASA Goddard Space Flight Center/Conceptual Image Lab/Adriana Manrique Gutierrez
Since the 60s of the 20th century, astronomers have been puzzled by how the Sun's supersonic "solar wind" – a stream of energetic particles flowing to the solar system – continues to retain energy after leaving the Sun. Now, the lucky arrangement of two spacecraft (one from the United States National Aerospace Agency and the other a joint ESA/United States NASA mission) may have revealed the answer. This discovery provides crucial insights that will help scientists improve predictions of solar activity affecting the space between the Sun and the Earth.
Solar Orbiter Illustration United States' Parker Solar Probe observes the Sun. Image Credit: Solar Orbiter: ESA/ATG medialab; Parker Solar Probe: United States NASA/Johns Hopkins Asia-Pacific Laboratory
Researchers recently published a paper in the journal Science presenting compelling evidence that the fastest solar wind is driven by magnetic "cyclones" (large kinks in the sun's magnetic field).
The co-leader of the study, the Center for Astrophysics | Yeimy Rivera, a postdoc at the Smithsonian Astrophysical Observatory under Harvard & Smithsonian, said: "Our study addresses a huge unanswered question about how the solar wind gets its energy, helping us understand how the sun affects its environment and ultimately the Earth." If this process takes place on our local stars, then it is highly likely that this will power winds from other stars in and around the Milky Way, and may have an impact on the habitability of exoplanets. "
Previously, United States' NASA's Parker Solar Probe found that these rotations are common throughout the solar wind. The Parker probe, which became the first vehicle to enter the Sun's magnetic atmosphere in 2021, allowed scientists to determine that the reflex becomes more pronounced and powerful closer to the Sun. However, so far, scientists have lacked experimental evidence to prove that this interesting phenomenon does deposit enough energy to play an important role in the solar wind.
Mike Stevens, an astrophysicist and co-author at the Center for Astrophysics, said: "About three years ago, I was talking about how fascinating these waves are in a presentation. Finally, an astronomy professor stood up and said, 'That's great, but do they really matter?' "
This conceptual image shows that the Parker Solar Probe is about to enter the corona. Photo credit: Ben Smith/Applied Physics Laboratory/United States NASA
To answer this question, the team of scientists had to use two different spacecraft. The Parker was built to travel through the Sun's atmosphere, or "corona". ESA and United States National Aeronautics and Space Administration (NASA) Solar Orbiter missions also orbit relatively close to the Sun and can measure the solar wind at greater distances.
This discovery was made possible by a coincidental alignment in February 2022 that allowed the Parker Solar Probe and Solar Orbiter to measure the same solar wind flow over two days. When the Parker probe circles the edge of the Sun's magnetic atmosphere, the solar orbiter is almost halfway through the Sun.
"We didn't initially realize that Parker and the Solar Orbiter were measuring the same thing. Parker saw that the plasma near the sun was slower and full of gyratory waves, while the solar orbiter recorded a fast stream that received heat and very little wave activity," said Samuel Badman, an astrophysicist at the Center for Astrophysics and another co-leader of the study. "When we connect the two, it's a real eureka moment."
Concept art of the artist showing the solar orbiter close to the Sun. Source: United States NASA Goddard Space Flight Center Conceptual Image Laboratory
Scientists have known for a long time that energy flows throughout the corona and the solar wind through so-called "Alfin waves", at least in part. These waves transmit energy through the plasma, which is the state of superheated matter that makes up the solar wind.
However, the evolution of the Alfeen wave between the Sun and the Earth and the extent of its interaction with the solar wind cannot be measured – until both missions are sent simultaneously closer to the Sun than ever before. Now, scientists can directly determine how much energy these waves store in the magnetic field and velocity fluctuations near the corona, while at greater distances from the sun, these waves carry much less energy.
New research suggests that Alfin waves, in the form of rotation, provide enough energy to explain the heating and acceleration phenomena recorded by the solar wind in its accelerated flow away from the Sun.
John Belcher, professor emeritus at the Massachusetts Institute of Technology, said: "It took us more than half a century to confirm that Alvenian wave acceleration and heating are important processes, and that they occur in much the same way as we think they occur." "
In addition to helping scientists better predict solar activity and space weather, this information also helps us understand the mysteries of the rest of the universe and how sun-like stars and stellar winds move everywhere.
"This discovery is one of the key pieces of the puzzle that answers the 50-year-old question of how the solar wind accelerates and heats up in the innermost layer of the heliosphere, bringing us closer to completing one of the main scientific goals of the Parker Solar Explorer mission," said Adam Szabo, scientific lead for NASA's Parker Solar Explorer mission.United States "
编译自/SciTechDaily