The ESA's Solar Orbiter records a solar "switchback" proving they exist

The new data could help explain why and how solar wind accelerates at great speeds across the solar system.
Chris Young
An artist's impression of the Solar Orbiter.
An artist's impression of the Solar Orbiter.

Source: ESA/ATG medialab 

The European Space Agency's Solar Orbiter probe made the first-ever remote sensing observation of a solar "switchback", according to a blog post from the agency.

The new data gathered by the mission sheds new light on a mysterious phenomenon that had only been hypothesized until now. It could help explain how solar wind is propelled across the solar system at incredibly fast speeds.

The 'first evidence of a switchback in the solar corona'

The ESA described its new observation as the "first evidence of a switchback in the solar corona". It was made using the Solar Orbiter's coronagraph instrument, called METIS. Solar switchbacks had only been hypothesized until now. NASA's Parker Solar Probe, for example, detected abrupt reversals in the sun's magnetic field, though it did not capture any imagery.

The ESA's Solar Orbiter probe was designed to take the most close-up images of the sun and collect data on its magnetic field. The probe observed the S-shaped structure, known as a switchback, in the solar plasma in March this year. The observation was published, alongside a new study, on Monday, September 12, in The Astrophysical Journal Letters.

NASA's Parker Solar Probe makes the closest approach any spacecraft has made to the sun, orbiting at distances within just a few million miles of the star's surface. Solar Orbiter keeps its distance by comparison. Orbiting a little further from the sun has the benefit of allowing the Solar Orbiter to equip and use imaging instruments, which would not be able to survive the closer approaches the Parker Solar Probe makes to the sun.

Scientists compared images taken by Solar Orbiter's cameras at different wavelengths and they found that the switchback phenomenon occurred just above an active sunspot — a cooler region of the sun characterized by dense and twisted magnetic fields.

Matching Solar Orbiter observations to mathematical models

The new observations seem to match mathematical models of switchback triggering developed by Zank, a space physicist at the University of Alabama in Huntsville. Zank's theory correctly predicted that switchbacks occur above sunspots when their magnetic field breaks and interacts with magnetic lines connected to the Solar System's interplanetary magnetic field.

"Rather like cracking a whip, this releases energy and sets an S-shaped disturbance traveling off into space, which a passing spacecraft would record as a switchback," Zank explained in the ESA's statement.

The switchback phenomenon was first spotted in METIS data on March 25 by Daniele Telloni, a solar physicist at the National Institute for Astrophysics in Torino, Italy.

The new observation could provide new insight into the surprising role of switchbacks throughout our solar system. Scientists believe they may play an important role in the acceleration and heating of the solar wind — a phenomenon that is currently unexplained by science.

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