Toward Measurement of Electron Pressure Anisotropy in Collisionless Laboratory Reconnection

The Terrestrial Reconnection EXperiment (TREX) at the Wisconsin Plasma Physics Laboratory (WiPPL) studies collisionless magnetic reconnection [1]. We've developed a new Pressure Anisotropy (PA) probe consisting of 24 langmuir probes; 12 outer tips collect plasma isotropically while the remaining 12 inner tips are shielded and receive plasma directionally. This allows us to measure plasma flows and pressure anisotropy during reconnection. With recent upgrades, we are now able to enter the collisionless kinetic regime of magnetic reconnection in which we expect electron anisotropy effects to dominate the physics in the ion diffusion region. This regime is relevant to reconnection in the magnetosphere. Embedded jets, seen in laboratory data, are driven into the outflow of reconnection as expected from spacecraft observation, theory, and simulations [2]. We’ve also observed signatures of pressure anisotropy with the PA probe. Current progress on probe design and analysis will be presented.

[1] Olson et al. PRL (2016) 116, 255001.http://dx.doi.org/10.1103/PhysRevLett.116.255001

[2] Wetherton et al. JGR Space Physics (2021) 125, e2020JA028604. https:// doi.org/10.1029/2020JA028604