Laboratory observation of plasmoid-dominated magnetic reconnection in hybrid collisional-collisionless regime

Abstract

Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasmas that occurs pervasively throughout the universe. In natural circumstances, the plasma properties on either side of the reconnection layer are almost asymmetric, in particular for the collision rates that critically determine the underlying reconnection mechanism. To date, all laboratory experiments on magnetic reconnections have been limited to purely collisional or collisionless regimes. Here, we report a well-designed experimental investigation on magnetic reconnections in a hybrid collisional-collisionless regime by interactions between laser-ablated copper and plastic plasmas. We directly observe the topology evolutions of the whole process of this asymmetric magnetic reconnection by highly-resolved proton radiography. Through this, we show that the growth rate of tearing instability in such a hybrid regime is still extremely large, resulting in rapid formation of multiple plasmoids and generation of plasmoid-dominated current sheet.

Electron stochastic acceleration in laboratory-produced kinetic turbulent plasmas

“…Due to the computational cost associated with kinetic simulations for the extensive temporal and spatial scales of the experiments, the majority of the simulations conducted were 2D3V. A self-similar transformation is proposed and implemented to establish a self-consistent connection between the PIC simulation and the radiation-magnetohydrodynamic (RMHD) simulation 47 , 48 . Initially, RMHD is employed to model the macroscopic states of plasmas, preceding the consideration of kinetic effects.…”

“…This scaling ensures that plasma properties, including β , β ram , the Mach number, and the Alfvén Mach number, the ratio of ion cyclotron times between the two systems ( ) et al, remain conserved between RMHD and PIC. The transformation equations are, where r , ρ , p , V , B, and t respectively represent length, density, pressure, velocity, magnetic field, and time, and more details of this transformation can refer to our previous work 47 .…”

Laboratory evidence of Weibel magnetogenesis driven by temperature gradient using three-dimensional synchronous proton radiography

“…However, although the Weibel magnetic field has been experimentally supported in nonrelativistic counterstreaming plasmas (32)(33)(34) and relativistic interpenetrating plasma beams (35)(36)(37)(38) driven by high-power lasers, the more universal and promising Weibel seeds driven solely by temperature gradients have not yet been experimentally confirmed. There are two key issues: On the one hand, it is necessary to create a plasma with a sufficiently large temperature gradient and a sufficiently weak Coulomb collision to achieve sufficient temperature anisotropy, which can be characterized by the dimensionless parameter α ≡ L T /λ e (39), where L T ≡ 1/∇ ln T e and λ e are respectively the temperature gradient scale and electron mean free path; on the other hand, laser-produced plasma is usually accompanied by a strong Biermann counterpart (40)(41)(42)(43)(44)(45)(46)(47)(48); therefore, the identification of the Weibel magnetic seeds may require multidirectional diagnosis, e.g., the proton radiography (49,50), especially for the unstable mode in different directions.…”

Currents in reconnection plasma jets: comparative study of laboratory experiments and spacecraft observations

“…Both limitations may be overcome in laboratory experiments of magnetic reconnection and current sheet dynamics (e.g. Frank 2010, Katz et al 2010, Yamada et al 2010, Greess et al 2022, Zhao et al 2022, where repetition of experiments (to a high degree of accuracy) allows one to separate spatial and temporal dynamics (see examples in Yamada et al 2000, 2016, Peterson et al 2021, Frank 2022. This has led to a persistent interest in simulating space plasma systems using laboratory plasma, including current sheets and magnetic reconnection (see reviews in Fälthammar 1974, Koepke 2008, Zweibel and Yamada 2009, Howes 2018, Peterson et al 2019, Liu et al 2021, Chien et al 2023.…”