Whip-cracking solar energy could explain the solar wind

Scientists have found the first direct evidence that the Sun’s magnetic field is rapidly changing direction, which could help explain the mysterious force propelling particles through our solar system.

© NASA/SDO
A solar flare captured in extreme ultraviolet light by NASA’s Solar Dynamics Observatory. Here we see a fiery orange-black sphere and at one point an incandescent explosion taking place.

Researchers observed the phenomenon using the Solar Orbiter probe, developed by the European Space Agency (ESA) and operated jointly with NASA. Launched into close orbit around the Sun in February 2020, the probe first detected the anomaly in our star’s magnetic field in March of this year. Using its Metis coronagraph to block out the glare of the sun’s disk and focus it on its edges, the probe captured images of a mysterious S-shaped bend in the tendrils of thin plasma pouring out of the sun’s corona, or upper atmosphere.

The scientists say the S-shaped kink is evidence that the Sun’s magnetic field is suddenly reversing — a long-suspected process known as magnetic switchback. Previously, spacecraft such as NASA’s Helios 1 and 2 probes and Parker Solar Probe have detected indirect evidence of switches in the Sun’s magnetic field, but this is the first time direct and visible evidence of an about-face has been captured. The researchers published their findings Sept. 12 in The Astrophysical Journal Letters.

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“I would say that this first image of a magnetic reversal in the solar corona has revealed the mystery of its origin,” said lead author Daniele Telloni, an astrophysicist at the Astrophysical Observatory of the National Institute for Astrophysics in Turin, Italy, in a statement.

Solar Orbiter photographed the kink on March 25, just a day before conducting a close flyby of the Sun that put the probe in orbit around Mercury. After comparing the image to an image of the Sun’s surface taken at the same time, the scientists determined that the S-shaped crease had appeared over a sunspot.

Sunspots are cooler, darker patches on the Sun where strong, knotted magnetic fields are created by the flow of the Sun’s electrically charged plasma. These fields, in turn, can affect the plasma in different ways, depending on whether they form open or closed circuits.

Closed-loop magnetic fields emerge at one point on the Sun’s surface and re-enter at another, forming vast, meandering arcs of electrified gas across the star. When these filaments collapse, they can release bursts of radiation called solar flares and fire explosive jets of solar material called coronal mass ejections (CMEs). Open magnetic field lines behave differently; They extend far into space and combine with the solar system’s magnetic field, creating a high-speed interplanetary highway that allows particles from the sun (the solar wind) to travel billions of miles.

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On planets with strong magnetic fields, such as our own, the planet’s magnetic field, or magnetosphere, absorbs the barrage of sun debris from the solar wind, triggering powerful geomagnetic storms. During these storms on Earth, waves of high-energy particles slightly compress our magnetic field. The particles then trickle down magnetic field lines near the poles, exciting molecules in the atmosphere, releasing energy in the form of light to create colorful auroras, like the ones that make up the Northern Lights.

Researchers believe serpentines occur across sunspots, where closed field lines break and connect to open ones. Similar to cracking a whip, this releases a burst of energy as the S-shaped serpentine is sent into space.

Proving that these serpentines exist could help scientists understand how solar winds can accelerate and heat up, even when they’re far from the Sun.

“This is exactly the result we hoped for with Solar Orbiter,” said Daniel Mueller, ESA project scientist for Solar Orbiter, in the statement. “With each orbit, we get more data from our suite of ten instruments. Based on results like these, we will refine the observations planned for Solar Orbiter’s next solar encounter to understand how the Sun connects to the broader magnet environment of the Solar System. This was Solar Orbiter’s first-ever close flyby of the Sun, so we expect many more exciting results.”

Originally published on Live Science.