New research reveals a surprising insight into the physics behind magnetic reconnection, a process occurring through the universe that converts magnetic to kinetic energy. The findings, by researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) together with other physicists, could lead to a greater ability to predict space weather – fast particles from the sun that can disrupt communications satellites and electrical networks.
Improved understanding could also lead to more efficient generation of the fusion energy that powers the sun and stars, which researchers are seeking to reproduce on Earth as a safe, clean, and abundant source of energy for generating electricity.
At PPPL, physicist Jongsoo Yoo and colleagues found that a type of wave in the region of space affected by Earth’s magnetic field could make reconnection more likely to occur. The wave creates friction in plasma, the state of matter composed of electrons and atomic nuclei, or ions, that makes up 99% of the visible universe by causing rubbing between the electrons and nuclei. The rubbing slows the electrons and enables the magnetic field lines in the plasma to tear apart and then reconnect, releasing enormous amounts of energy.
“These short-wavelength waves could transfer momentum between electrons and ions and help speed up reconnection,” said Yoo, whose research appears in a paper published in Geophysical Research Letters. “That’s the takeaway.”
Yoo used data from measurements by the Magnetospheric Multiscale Mission, a group of four spacecraft launched by NASA in 2015, to study the waves. The mission is flying in tight formation to study magnetic reconnection, which occurs throughout the universe, in the magnetic field surrounding Earth.
Magnetic reconnection on the surface of the sun is responsible for solar flares, huge burps of charged particles known as coronal mass ejections, and the aurora borealis. Reconnection can also occur inside doughnut-shaped plasma facilities known as tokamaks to create the conditions for fusion, which combines light elements in the form of plasma to generate massive amounts of energy.
The new findings could also help explain unexpected heating that occurs in the Magnetic Reconnection Experiment (MRX), a device at PPPL that studies reconnection in the laboratory. “During MRX experiments, we see unexplained heating all the time, but haven’t been able to identify what causes it,” Yoo said. “These short-wavelength waves could be a good candidate.”
The discovery builds on research that PPPL physicist Hantao Ji, a professor of astrophysical sciences at Princeton University completed decades ago. “Previously, it seemed like these waves might not be important,” Ji said. “But Jongsoo was able to show that they are likely important under different conditions. That is a happy surprise.”
Yoo plans to complete data analysis that could provide further evidence that these short-wavelength waves can impact reconnection. “I am very excited about this next step,” Yoo said. “If you can prove that these waves have an effect on reconnection, that would have a very big impact.”
Support for this research came from the DOE’s Office of Science, NASA, and the National Science Foundation. Collaborators include physicists from Utah State University, the University of Rochester, the NASA Goddard Space Flight Center, Princeton University, and China’s Harbin Institute of Technology.