Characterization of Quasi-Keplerian, Differentially Rotating, Free-Boundary Laboratory Plasmas

Abstract

We present results from pulsed-power driven differentially rotating plasma experiments designed to simulate physics relevant to astrophysical disks and jets. In these experiments, angular momentum is injected by the ram pressure of the ablation flows from a wire array Z pinch. In contrast to previous liquid metal and plasma experiments, rotation is not driven by boundary forces. Axial pressure gradients launch a rotating plasma jet upwards, which is confined by a combination of ram, thermal, and magnetic pressure of a surrounding plasma halo. The jet has subsonic rotation, with a maximum rotation velocity 23 ± 3 km/s. The rotational velocity profile is quasi-Keplerian with a positive Rayleigh discriminant κ 2 ∝ r −2.8±0.8 rad 2 /s 2 . The plasma completes 0.5 − 2 full rotations in the experimental time frame (∼ 150 ns).

New Class of Laboratory Astrophysics Experiments: Application to Radiative Accretion Processes around Neutron Stars

“…Furthermore, although numerical simulations continue to be the only means to study these phenomena, their validity remains to be assessed. The framework for scaling astrophysical phenomena to the laboratory (Ryutov et al 1999;Falize et al 2011a) has been the basis for many high-energy density plasma experiments, such as those studying physical processes relevant to accretion shocks (Falize et al 2012;Krauland et al 2012Krauland et al , 2013Cross et al 2016;Revet et al 2017;Van Box Som et al 2018;Mabey et al 2019), magnetized stellar jets (Lebedev et al 2005;Ciardi et al 2007Ciardi et al , 2009Ciardi et al , 2013Albertazzi et al 2014;Revet et al 2021), supernova remnants (Kuranz et al 2018;Rigon et al 2019;Albertazzi et al 2020), or accretion disks (Valenzuela-Villaseca et al 2022). However, these similarity concepts require experiments to reach the same physical regime as found in astrophysics, as well as to keep the microphysics of the two systems similar.…”