A strange phenomenon thought to only exist near the Sun has been detected in Earth's magnetic field for the first time. The discovery could help scientists forecast the impact of geomagnetic storms more accurately.
Physicists Emily McDougall and Matthew Argall at the University of New Hampshire detected unexpected structures in the plasma caught in Earth's magnetic field. The plasma seemed to have been rotating slowly before snapping back to its original orientation, creating zigzag-shaped kinks called magnetic switchbacks.
While these switchbacks haven't been seen in Earth's magnetic field before, they are reminiscent of structures seen in the plasma constantly blasting out of the Sun. And it turns out the two may be linked.
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On closer examination, the team found that not all of the plasma caught in Earth's magnetic field was from our planet – some of it had come from the Sun, mixing with locally sourced charged particles. That interaction caused the magnetic field to break and reconnect, creating the characteristic zigzags.
Sun-studying spacecraft have seen signs of switchbacks for decades. Though there are a few competing theories explaining their origins, they seem to form when two different types of magnetic field lines interact.
Open field lines point directly away from the Sun, streaming out into space and carrying plasma that we call the solar wind. Closed field lines, however, travel outwards for a relatively short distance, then reverse course and curve back into the Sun.
When open field lines form near a set of closed magnetic fields, they can break apart and reconnect with one another. Plasma on the outer edge of a closed loop is pulled back toward the Sun, only to be guided into the open field lines, taking it out into space. Interactions between the lines in this S-shaped wave release bursts of energy that 'kinks' the field lines – this is a switchback.
McDougall and Argall identified signs of a similar structure in Earth's magnetic field while analyzing data from NASA's Magnetospheric Multiscale mission. In this case, the open field lines are those streaming in from the Sun, which interact with the closed field lines looping around Earth.
"This discovery, " the researchers write, "provides new clues about how similar disturbances can form at the boundary between different regions of plasma, which allows for future study of related events in the Sun's outer layers without needing to send spacecraft directly into those extreme conditions."
The research was published in the Journal of Geophysical Research: Space Physics.