Onset of magnetic reconnection in thick, driven current sheets via multiple interacting resonant sublayers

Much progress has been made in understanding the basic kinetic plasma physics of magnetic reconnection via in situ spacecraft observations and well diagnosed and reproducible laboratory experiments. However, extrapolating the results from these kinetic-scale current sheets to large astrophysical reconnecting systems poses a key challenge, due to the vast separation of scales present [1].

Here, we demonstrate a novel onset scenario that may occur in three-dimensional simulations of thick current sheets. By driving the thick layer at the upstream boundary via an electric field with multiple modes of different helicity, we demonstrate that multiple kinetic-scale sub-layers can form simultaneously at rational surfaces that are resonant with this boundary drive. These sub-layers can pinch together due to their strong currents and undergo tearing instabilities to produce secondary magnetic islands that overlap between layers. These simulations suggest a possible mechanism to produce thick, turbulent reconnecting current sheets in first-principles kinetic simulations with developed reconnection outflow jets.

[1] Ji, H., Daughton, W., Jara-Almonte, J., Le, A., Stanier, A., & Yoo, J. (2022). Magnetic reconnection in the era of exascale computing and multiscale experiments. Nature Reviews Physics, 4(4), 263-282.