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NASA’s Parker Solar Probe Spies Solar Wind ‘U-Turn’
Images captured by NASA’s Parker Solar Probe as the spacecraft made its record-breaking closest approach to the Sun in December 2024 have now revealed new details about how solar magnetic fields responsible for space weather escape from the Sun — and how sometimes they don’t.
Like a toddler, our Sun occasionally has disruptive outbursts. But instead of throwing a fit, the Sun spews magnetized material and hazardous high-energy particles that drive space weather as they travel across the solar system. These outbursts can impact our daily lives, from disrupting technologies like GPS to triggering power outages, and they can also imperil voyaging astronauts and spacecraft. Understanding how these solar outbursts, called coronal mass ejections (CMEs), occur and where they are headed is essential to predicting and preparing for their impacts at Earth, the Moon, and Mars.
Images taken by Parker Solar Probe in December 2024, and published Thursday in the Astrophysical Journal Letters, have revealed that not all magnetic material in a CME escapes the Sun — some makes it back, changing the shape of the solar atmosphere in subtle, but significant, ways that can set the course of the next CME exploding from the Sun. These findings have far-reaching implications for understanding how the CME-driven release of magnetic fields affects not only the planets, but the Sun itself.
“These breathtaking images are some of the closest ever taken to the Sun and they’re expanding what we know about our closest star,” said Joe Westlake, heliophysics division director at NASA Headquarters in Washington. “The insights we gain from these images are an important part of understanding and predicting how space weather moves through the solar system, especially for mission planning that ensures the safety of our Artemis astronauts traveling beyond the protective shield of our atmosphere.”
Parker Solar Probe reveals solar recycling in action
As Parker Solar Probe swept through the Sun’s atmosphere on Dec. 24, 2024, just 3.8 million miles from the solar surface, its Wide-Field Imager for Solar Probe, or WISPR, observed a CME erupt from the Sun. In the CME’s wake, elongated blobs of solar material were seen falling back toward the Sun.
This type of feature, called “inflows”, has previously been seen from a distance by other NASA missions including SOHO (Solar and Heliospheric Observatory, a joint mission with ESA, the European Space Agency) and STEREO (Solar Terrestrial Relations Observatory). But Parker Solar Probe’s extreme close-up view from within the solar atmosphere reveals details of material falling back toward the Sun and on scales never seen before.
“We’ve previously seen hints that material can fall back into the Sun this way, but to see it with this clarity is amazing,” said Nour Rawafi, the project scientist for Parker Solar Probe at the Johns Hopkins Applied Physics Laboratory, which designed, built, and operates the spacecraft in Laurel, Maryland. “This is a really fascinating, eye-opening glimpse into how the Sun continuously recycles its coronal magnetic fields and material.”
Insights on inflows
For the first time, the high-resolution images from Parker Solar Probe allowed scientists to make precise measurements about the inflow process, such as the speed and size of the blobs of material pulled back into the Sun. These previously hidden details provide scientists with new insights into the physical mechanisms that reconfigure the solar atmosphere.
The CMEs are often triggered by twisted magnetic field lines that explosively snap and realign in a process called magnetic reconnection. This magnetic explosion kicks out a burst of charged particles and magnetic fields — a CME.
As the CME travels outward from the Sun, it expands, in some cases causing nearby magnetic field lines to tear apart like the threads of an old piece of cloth pulled too tight. The torn magnetic field quickly mends itself, creating separate magnetic loops. Some of the loops travel outward from the Sun, and others stitch back to the Sun, forming inflows.
“It turns out, some of the magnetic field released with the CME does not escape as we would expect,” said Angelos Vourlidas, WISPR project scientist and researcher at Johns Hopkins Applied Physics Laboratory. “It actually lingers for a while and eventually returns to the Sun to be recycled, reshaping the solar atmosphere in subtle ways.”
An important result of this magnetic recycling is that as the inflows contract back into the Sun, they drag down blobs of nearby solar material and ultimately affect the magnetic fields swirling beneath. This interaction reconfigures the solar magnetic landscape, potentially altering the trajectories of subsequent CMEs that may emerge from the region.
“The magnetic reconfiguration caused by inflows may be enough to point a secondary CME a few degrees in a different direction,” Vourlidas said. “That’s enough to be the difference between a CME crashing into Mars versus sweeping by the planet with no or little effects.”
Scientists are using the new findings to improve their models of space weather and the Sun’s complex magnetic environment. Ultimately, this work may help scientists better predict the impact of space weather across the solar system on longer timescales than currently possible.
“Eventually, with more and more passes by the Sun, Parker Solar Probe will help us be able to continue building the big picture of the Sun’s magnetic fields and how they can affect us,” Rawafi said. “And as the Sun transitions from solar maximum toward minimum, the scenes we’ll witness may be even more dramatic.”
By Mara Johnson-Groh
NASA’s Goddard Space Flight Center, Greenbelt, Md.
