Characterizing Sheared Magnetic Arcade Equilibria

Magnetized plasma arcades appear in space and astrophysical contexts and have recently been the focus of laboratory, observational, and computational studies. We characterize equilibria of sheared magnetic arcades in the Wheaton Impulsive Reconnection Experiment (WIRX). We analyze sheared magnetic arcade height, length, thickness, shear angle profile, and their dependence on current, vacuum magnetic field strength, and length of cathode. We use ICCD cameras and magnetic field probes to characterize the discharges. The ICCD cameras infer plasma parameters from optical emission across the entire plasma at two distinct times. The magnetic field probe measures magnetic fields directly at an array of vertical positions through time but is sensitive to the proximity of the plasma to the probe. We find that the length (L), height (H), and thickness (Δ) of the arcade increase with current (I). At high I, length saturates at the full length of the cathode. Shear angle varies continuously in the region where J is strong yet the ICCD image only reveals one preferred angle. Lastly, the quantity B / J, which in this case is Δ L B / I, is useful as a sorting parameter for distinguishing between forms of arcade.