Explaining Mystery Behind Fast Magnetic Reconnection

Researchers establish the physics that allows fast magnetic explosions in house.

When magnetic discipline strains of reverse instructions merge, they create explosions that may launch great quantities of vitality. The merging of opposing discipline strains on the solar creates photo voltaic flares and coronal mass ejections, that are large blasts of vitality that may journey to Earth in lower than a day.

While the overall mechanics of magnetic reconnection are effectively understood, researchers have struggled for over a half-century to clarify the exact physics behind the fast vitality launch that happens.

A brand new Dartmouth analysis examine printed yesterday (April 28, 2022) within the journal Communications Physics gives the primary theoretical description of how a phenomenon generally known as the “Hall effect” determines the effectivity of magnetic reconnection.

Magnetic reconnection happens when magnetic discipline strains of reverse instructions merge, rejoin, and snap aside, releasing large quantities of vitality to warmth plasmas and drive high-speed outflows. Credit: Yi-Hsin Liu/Dartmouth College

“The rate at which magnetic field lines reconnect is of extreme importance for processes in space that can impact Earth,” stated Yi-Hsin Liu, an assistant professor of physics and astronomy at Dartmouth. “After decades of effort, we now have a full theory to address this long-standing problem.”

Magnetic reconnection exists all through nature in plasmas, the fourth state of matter that fills a lot of the seen universe. Reconnection takes place when magnetic discipline strains of reverse instructions are drawn to one another, break aside, rejoin, after which violently snap away.

In the case of magnetic reconnection, the snapping of magnetic strains forces out magnetized plasma at high velocities. The energy is created and displaced to plasmas through a tension force like that which ejects objects from slingshots.

Around the region where reconnection occurs, the departure of the ion motion (blue streamlines in (a)) from the electron motion (red streamlines in (a)) gives rise to the “Hall effect,” which results in the electromagnetic energy transport pattern illustrated by yellow streamlines in (b). This transport pattern limits the energy conversion at the center, enabling fast reconnection. Credit: Yi-Hsin Liu/Dartmouth College

The Dartmouth research focused on the reconnection rate problem, the key component of magnetic reconnection that describes the speed of the action in which magnetic lines converge and pull apart.

Previous research found that the Hall Effect— the interaction between electric currents and the magnetic fields that surround them—creates the conditions for fast magnetic reconnection. But until now researchers were unable to explain the details of how exactly the Hall effect enhances the reconnection rate.

The Dartmouth theoretical study demonstrates that the Hall effect suppresses the conversion of energy from the magnetic field to plasma particles. This limits the amount of pressure at the point where they merge, forcing the magnetic field lines to curve and pinch, resulting in open outflow geometry needed to speed up the reconnection process.

Dartmouth’s Xiaocan Li, postdoctoral researcher (left); Yi-Hsin Liu, Assistant Professor of Physics and Astronomy (center); Shan-Chang Lin, PhD candidate (right). Credit: Robert Gill/Dartmouth College

“This theory addresses the important puzzle of why and how the Hall effect makes reconnection so fast,” said Liu, who serves as deputy lead of the theory and modeling team for NASA’s Magnetospheric Multiscale Mission (MMS). “With this research, we also have explained the explosive magnetic energy release process that is fundamental and ubiquitous in natural plasmas.”

The new theory could further the technical understanding of solar flares and coronal mass ejection events that cause space weather and electrical disturbances on Earth. In addition to using the reconnection rate to estimate the time scales of solar flares, it can also be used to determine the intensity of geomagnetic substorms, and the interaction between the solar wind and Earth’s magnetosphere.

Yi-Hsin Liu, Assistant Professor of Physics and Astronomy, Dartmouth College. Credit: Robert Gill/Dartmouth College

The research team, funded by the National Science Foundation (NSF) and NASA, is working alongside NASA’s Magnetospheric Multiscale Mission to analyze magnetic reconnection in nature. Data from four satellites flying in tight formation around Earth’s magnetosphere as part of the NASA mission will be used to validate the Dartmouth theoretical finding.

“This work demonstrates that fundamental theory insights reinforced by modeling capabilities can advance scientific discovery,” said Vyacheslav Lukin, a program director for plasma physics at NSF. “The technological and societal implications of these results are intriguing as they can help predict impacts of space weather on the electrical grid, develop new energy sources, and explore novel space propulsion technologies.”

The new study can also inform reconnection studies in magnetically confined fusion devices and astrophysical plasmas near neutron stars and black holes. Although there is no current applied use, some researchers have considered the possibility of using magnetic reconnection in spacecraft thrusters.

Reference: “First-principles theory of the rate of magnetic reconnection in magnetospheric and solar plasmas” by Yi-Hsin Liu, Paul Cassak, Xiaocan Li, Michael Hesse, Shan-Chang Lin and Kevin Genestreti, 28 April 2022, Communications Physics.
DOI: 10.1038/s42005-022-00854-x

This work is funded by the NSF’s PHY and AGS Divisions, NASA’s Magnetospheric Multiscale (MMS) mission, and the U.S. Department of Energy.

Co-authors of the study are Paul Cassak, West Virginia University; Xiaocan Li, Dartmouth; Michael Hesse, NASA’s Ames Research Center; Shan-Chang Lin, Dartmouth; and Kevin Genestreti, Southwest Research Institute.