This paper describes ZEUS-MP, a multi-physics, massively parallel, message-passing implementation of the ZEUS code. ZEUS-MP differs significantly from the thoroughly documented ZEUS-2D code, the completely undocumented (in peer-reviewed literature) ZEUS-3D code, and a marginally documented "version 1" of ZEUS-MP first distributed publicly in 1999. ZEUS-MP offers an MHD algorithm which is better suited for multidimensional flows than the ZEUS-2D module by virtue of modifications to the Method of Characteristics scheme first suggested by Hawley & Stone (1995). This MHD module is shown to compare quite favorably to the TVD scheme described by Ryu et al. (1998). ZEUS-MP is the first publicly-available ZEUS code to allow the advection of multiple chemical (or nuclear) species. Radiation hydrodynamic simulations are enabled via an implicit flux-limited radiation diffusion (FLD) module. The hydrodynamic, MHD, and FLD modules may be used, singly or in concert, in one, two, or three space dimensions. Additionally, so-called "1.5-D" and "2.5-D" grids, in which the "half-D" denotes a symmetry axis along which a constant but non-zero value of velocity or magnetic field is evolved, are supported. Self gravity may be included either through the assumption of a GM/r potential or a solution of Poisson's equation using one of three linear solver packages (conjugategradient, multigrid, and FFT) provided for that purpose. Point-mass potentials are also supported.Because ZEUS-MP is designed for large simulations on parallel computing platforms, considerable attention is paid to the parallel performance characteristics of each module in the code. Strong-scaling tests involving pure hydrodynamics (with and without self-gravity), MHD, and RHD are performed in which large problems (256 3 zones) are distributed among as many as 1024 processors of an IBM SP3. Parallel efficiency is a strong function of the amount of communication required between processors in a given algorithm, but all modules are shown to scale well on up to 1024 processors for the chosen fixed problem size.

We report the first measurements of the formation and structure of a magnetized collisionless shock by a laser-driven magnetic piston in a current-free laboratory plasma. This new class of experiments combines a high-energy laser system and a large magnetized plasma to transfer energy from a laser plasma plume to the ambient ions through collisionless coupling, until a self-sustained M A ∼ 2 magnetosonic shock separates from the piston. The ambient plasma is highly magnetized, current free, and large enough (17 m × 0.6 m) to support Alfvén waves. Magnetic field measurements of the structure and evolution of the shock are consistent with two-dimensional hybrid simulations, which show Larmor coupling between the debris and ambient ions and the presence of reflected ions, which provide the dissipation. The measured shock formation time confirms predictions from computational work.

Two-dimensional hybrid simulations of perpendicular collisionless shocks are modeled after potential laboratory conditions that are attainable in the LArge Plasma Device (LAPD) at the University of California, Los Angeles Basic Plasma Science Facility. The kJ class 1053 nm Nd:Glass Raptor laser will be used to ablate carbon targets in the LAPD with on-target energies of 100-500 J. The ablated debris ions will expand into ambient, partially ionized hydrogen or helium. A parameter study is performed via hybrid simulation to determine possible conditions that could lead to shock formation in future LAPD experiments. Simulation results are presented along with a comparison to an analytical coupling parameter.

The dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma was investigated with magnetic flux probes and Langmuir probes. Debris-ions expanding at super-Alfv enic velocity (up to M A ¼ 1:5) expel the ambient magnetic field, creating a large (>20 cm) diamagnetic cavity. We observe a field compression of up to B=B 0 ¼ 1:5 as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston and swept outside the bubble volume. Nonlinear shear-Alfv en waves (dB=B 0 > 25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave. V

Experiments, analytic modeling, and numerical simulations are presented to characterize carbon plasmas produced by high-intensity (109−1013 W cm−2) lasers relevant to experimental laboratory astrophysics. In the large-scale limit, the results agree well with a self-similar isentropic, adiabatic fluid model. Laser-target simulations, however, show small-scale structure in the velocity distribution of different ion species, which is also seen in experiments. These distributions indicate that most of the plasma energy resides in moderate charge states (C+3–C+4), most of the mass resides in the lowest charge states, and the highest charge states move fastest.