New theory explains mystery behind fast magnetic reconnection
When magnetic field lines of opposite directions merge, they create explosions that can release massive amounts of energy. On the sun, the merging of opposing field lines causes solar flares and coronal mass ejections, giant ...
While the general mechanics of magnetic reconnection are known, researchers have struggled for over a half-century to explain the precise physics behind the rapid energy release that takes place.
A new Dartmouth study published in Communications Physics provides the first theoretical description of how a phenomenon known as the "Hall effect" determines the efficiency of magnetic reconnection.
"The rate at which magnetic field lines reconnect is of extreme importance for processes in space that can impact Earth," said 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 throughout nature in plasmas, the fourth state of matter that fills most of the visible universe. Reconnection takes place when magnetic field lines of opposite directions are drawn to each other, break apart, rejoin, and then violently snap away.
In the case of magnetic reconnection, the snapping of magnetic lines 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.
The Dartmouth study focuses 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.
Solar flares and coronal mass ejections on the sun are caused by “magnetic reconnection”—when magnetic field lines of opposite directions merge, rejoin and snap apart, creating explosions that release massive amounts of energy. Credit: NASA Conceptual Image Laboratory.
Magnetic reconnection occurs when magnetic field lines of opposite directions merge, rejoin, and snap apart, releasing massive amounts of energy to heat plasmas and drive high-speed outflows. Credit: Yi-Hsin Liu/Dartmouth College
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