Magnetic reconnection phenomena described with just two terms

Magnetic reconnection – the process by which a magnetic field releases energy by changing its topology – is typically described using the generalized Ohm’s law, which may require up to seven terms. In a recent paper, Yoon and Bellan present an alternative framework for studying magnetic reconnection with just two terms.

The proposed technique begins with canonical vorticity – the curl of the canonical momentum – as the fundamental quantity of interest rather than the magnetic field, as is used in traditional methods. The researchers then introduce the “electron canonical battery” term, related to gradients of the electron pressure tensor and accounting for kinetic effects present in the system, including electron viscosity. Combined with the convective term describing magnetic reconnection for the case of frozen-in canonical vorticity, the model can provide an ab initio description of electron physics in the system.

“The canonical battery term is the only possible such term, so once the canonical battery term is included, the framework is exhaustive,” said author Young Dae Yoon.

To test their model, the researchers conducted a numerical simulation of a magnetic perturbation on an initially force-free equilibrium system. The simulation confirmed that magnetic reconnection can be predicted by considering just the competition between the electron canonical battery and convective terms. Using this simplified framework, one can easily study how a specific kinetic effect influences reconnection.

The authors note the method is generalizable to other particles. “The equation involving canonical vorticity is actually valid not only for electrons, but also for any other species,” Yoon said. “Thus, it would be interesting to examine the dynamics of the canonical vorticities of each species in various plasma phenomena.”

Source: “The electron canonical battery effect in magnetic reconnection: Completion of the electron canonical vorticity framework,” by Young Dae Yoon and Paul M. Bellan, Physics of Plasmas (2019). The article can be accessed at https://doi.org/10.1063/1.5122225 .