Laboratory Experiments in the Collisionless Kinetic Regime of Magnetic Reconnection*

The Terrestrial Reconnection EXperiment (TREX)[1] at the Wisconsin Plasma Physics Laboratory (WiPPL)[2] can reliably reach the collisionless kinetic reconnection regime by driving a magnetic field via a cylindrical coil geometry.  The most resent upgrade to the TREX configuration is the Drive Cylinder, which creates asymmetric reconnection that generates a ~2m long current layer with a normalized system size of L/d_i ≈ 13.  Compared to the previous TREX systems, the lower inductance of the Drive Cylinder has increased the reconnection rate from E_rec ≈ 100V/m to 900V/m.  With these improved parameters, the Drive Cylinder produces reconnection events with Lundquist numbers up to S ≈ 10⁵. These upgrades reduce the effects of collisionality in the experiment, such that electron pressure anisotropy is expected to develop unimpeded.  By operating in this regime with a highly reproducible plasma, the Drive Cylinder aims to investigate plasma dynamics in the electron diffusion region similar to spacecraft data observed in the Earth's magnetosphere.

[1] Experimental Demonstration of the Collisionless Plasmoid Instability below the Ion Kinetic Scale during Magnetic Reconnection J.Olson et al, Phys. Rev. Lett., 116, 255001 (2016)

[2] The Wisconsin Plasma Astrophysics Laboratory C. B. Forest et al., J Plasma Physics, 81, Oct 2015.