Creation of a Hall-MHD Parker Spiral in the Lab*

When magnetically-dominated plasma co-rotating with the Sun expands outward it transitions to flow-dominated as the magnetic field strength drops. At that point it can stretch, bend, and break the dipolar fieldlines of the Sun - carrying a spiraling magnetic field out into the solar system known as the Parker Spiral. The evolution of plasma through this transitional region where M_A ≈ 1 (known as the Alfvén surface) has never been accessible to any in-situ satellite measurements until now (Parker Solar Probe will be the first) but is readily accessible with novel laboratory experiments on the Big Red Plasma Ball (BRB) at the Wisconsin Plasma Physics Lab. The experiment uses a SmCo permanent magnet and J x B stirring to produce a rapidly rotating magnetosphere that can give rise to the formation of an Alfvén critical point and the Parker Spiral. NIMROD MHD simulations performed with experimental parameters and current injection confirm the production of a rotating magnetosphere, radial wind, Alfvén critical point, and Parker Spiral as well as axisymmetric plasmoids in the magnetospheric current sheet. 2D maps of magnetic data taken from a three-axis hall sensor array during the experiment show clear formation of an Alfvén surface, a Syrovatskii layer, and a magnetic Parker Spiral. The Parker spiral current sheet region is quite dynamic with coherent magnetic and density fluctuations that are consistent with plasmoid ejection. Experimental magnetic data agrees very well with NIMROD MHD simulations but significant discrepancies arise between the simulated ion flow and experimental measurements that implicate the important role of two-fluid effects in this Hall-dominated experimental Parker Spiral.