Solar switchbacks are sudden, large radial deflections of the solar wind magnetic field, previously revealed in interplanetary space by NASA spacecraft.
This image, obtained with the Metis instrument onboard ESA’s Solar Orbiter on March 25, 2022, shows the solar corona. Image credit: Telloni et al., doi: 10.3847/2041-8213/ac8104.
The solar wind is a continuous flow of charged particles streaming from the Sun’s outermost atmosphere, the solar corona, into interplanetary space.
It is characterized by the coexistence of large-scale structures of solar origin, turbulent fluctuations, magnetohydrodynamic and kinetic plasma waves and instabilities, associated with physical processes such as magnetic reconnection, shocks, and a broad range of processes, which result in particle heating and energization.
The solar wind acceleration mechanisms, its complex dynamics and interaction with the solar magnetic field, and the observed plasma heating are still outstanding questions in heliophysics.
One interesting solar wind feature emerging from spacecraft measurements is the puzzling existence of abrupt, temporary magnetic field reversals.
Named magnetic switchbacks, these reversals were first observed in the 1990s by NASA’s Ulysses spacecraft and, more recently, extensively measured by NASA’s Parker Solar Probe.
“A switchback is basically a propagating kink in a magnetic field, with the most extreme case being an almost S-shaped kink in the field line that reverses its direction twice,” said Dr. Gary Zank, director of the Center for Space Plasma and Aeronomic Research and the Aerojet Rocketdyne chair of the Department of Space Science at the University of Alabama in Huntsville.
“In other words, it’s a somewhat complicated wave with an unusual wave form.”
In the research, Dr. Zank and colleagues analyzed the images of the solar corona obtained by the Metis coronagraph onboard ESA’s Solar Orbiter on March 25, 2022.
“Unlike plasma measurements that make point measurements locally and temporally, Metis provides a global observation of the full structure,” Dr. Zank said.
“So, to see the global structure of a switchback was both unexpected and remarkable after staring at plasma plots and inferring the geometry of a switchback indirectly
“This is a very strong confirmation of the basic theory I had advanced in our 2020 paper.”
The researchers theorized that switchbacks originate due to the reconnection of the solar magnetic field above the surface of the Sun.
That explained what Parker Solar Probe observed, and a statistical comparison of the theory with those observations was performed.
“This was very promising but it could not eliminate other possible explanations for the origin of the switchbacks,” Dr. Zank said.
“However, with the global observation of a switchback enabled by the Metis instrument, we applied the same theory to explain the global observations successfully and eliminate alternate explanations.”
The team’s paper will appear in the Astrophysical Journal Letters.
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Daniele Telloni et al. 2022. Observation of Magnetic Switchback in the Solar Corona. ApJL, in press; doi: 10.3847/2041-8213/ac8104
Source link: https://www.sci.news/astronomy/solar-switchback-11185.html
