We review our recent numerical simulations of star formation. First, we show a simulation of magnetic turbulence in a plate-shaped self-gravitating stratified cloud. We find that the cloud is lifted up by the pressure of magnetic turbulence and reaches a steady-state characterized by oscillations about a new time-averaged equilibrium state. Next, we present a numerical simulation of gravitational fragmentation of the plate-shaped magnetized cloud. For strong magnetic field cases, we confirm that the gravitational instability develops gradually on a time scale characteristic of ambipolar diffusion. Finally, a numerical simulation of jet formation is shown. The important factors of jet formation are the magnetic field and rotation of a disk around a star.

The dominant roles of pressure tensors in collisionless magnetic reconnection are demonstrated during a steady state of two-dimensional collisionless driven reconnection without any guide field by means of full-particle simulations. The pressure tensors in the momentum equations of ions and of electrons play two crucial roles in the collisionless magnetic reconnection. One role is the gyroviscous cancellation which suppresses the violation of frozen-in condition due to the inertia term. This cancellation causes ions to be tied to the magnetic field within the ion skin depth. The gyroviscous cancellation of electrons is also observed. The other role is a strong violation of the frozen-in condition due to non-gyrotropic pressure. The strong violation of the ion frozen-in condition forms the ion-dissipation region where the collisionless magnetic reconnection occurs. The strong violation of the electron frozen-in condition generates the reconnection electric field at the reconnection point.

Fast ignition is an epoch-making scheme for inertial fusion energy. In this scheme, the formation of high-density core plasma is one of the key issues which must be solved, because the implosion dynamics of the fast ignition target, which is non-spherical with a conical target, is quite different from that of the conventional central ignition target. Some previous works showed the possibility of formation of a high-density core. However, the effects of hydrodynamic instability were not discussed in those works. In this paper, we simulate the whole implosion dynamics of a perturbed non-spherical target, and the effect of radiation transport instability is estimated using the two-dimensional integrated implosion (radiation hydrodynamics) code PINOCO. In the result, we have found that the hydrodynamic instabily has less of an effect on the formation of high-density core plasma in the cone-guided implosion, in comparision with the spherical implosion.

Broadband coherent emission around the electron plasma frequency can be produced from a laser wakefield by linear mode conversion in inhomogeneous plasmas. In addition to its potential use as a powerful terahertz source, it can be used as diagnostics of the wakefield produced for particle acceleration. In this paper, some simulation results are presented on the wake emission when the wakefield is driven in the wavebreaking regime and driven inside a plasma channel.

We describe a general multi-scale method to model hydrogen isotope transport, over length scales from angstroms to centimeters and time scales from picoseconds to several seconds, in a complex three-dimensional porous geometry using molecular dynamics, kinetic Monte Carlo and Monte Carlo diffusion simulations. We present comparisons with experimental results for hydrogen diffusion and hydrogen atom desorption from graphite. Finally, we demonstrate the flexibility of the computational tools used to tackle problems at different scales.

Hydrogen adsorption by graphite is examined by classical molecular dynamics simulation using a modified Brenner reactive empirical bond order (REBO) potential. Such interactions are typical in chemical sputtering experiments, and knowledge of the fundamental behavior of hydrogen and graphene in collisional conditions is essential for modeling the sputtering mechanism. The hydrogen adsorption rate is found to be dependent on the incident hydrogen energy and not on graphene temperature. Rather than destroying the graphene, hydrogen incidence at energies of less than 100 eV can be classified into three regimes of adsorption, reflection and penetration through one or more graphene layers. Incidence at the lowest energies is shown to distort the graphene structure.

A three-dimentional particle–particle particle–mesh (P3M) model for dusty plasma has been developed. The model implies a fully kinetic description for all species in the plasma, being able to resolve the finite size effects for dust grains. The model was used for simulation of charging process for the dust grains in a capacitive radiofrequency discharge.

This paper is devoted to first-principles calculations of hydrogen and helium thermodynamics. We use the direct path integral Monte Carlo method to compute isochors and isotherms in a wide range of parameters in comparison with available theoretical and experimental results. New results for hydrogen and hydrogen–helium plasmas with the mass concentration of helium $Y\,{=}\,0.988$ are analysed with the help of a model based on the chemical picture.

The drift model is an extention of magnetohydrodynamics (MHD) with the ion finite Larmor radius effects. It is demostrated with a one-dimensional simulation code that the dispersion relation of the kinetic Alfvén wave is reproduced with the drift model. The simulation code for MHD and energetic alpha particles (MEGA) has been extended with the drift model and an extended Ohm's law where the electron Landau damping is taken into account with the Landau fluid model. The linear stability of the alpha-particle driven Alfvén eigenmode in the Tokamak Fusion Test Reactor (TFTR) deuterium-tritium (D-T) plasma was investigated with the extended MEGA code. The nonlinear simulation results of an ITER-like plasma with a weak negative shear are presented.

Zonal flow behaviour and its effect on turbulent transport in reversed magnetic shear tokamaks are investigated by global simulations of electrostatic ion temperature gradient driven turbulence. When the safety factor $q$ is reduced, zonal flows in a minimum $q$ region change from oscillatory to stationary and suppress the turbulent transport effectively. This result indicates that the change of zonal flow behaviour in the minimum $q$ region may trigger the formation of ion transport barriers.

Collisionless time evolutions of geodesic acoustic modes (GAMs) in tokamaks are investigated by the gyrokinetic theory and simulation. It is shown that the collisionless damping of the GAM oscillations is enhanced when the ratio of the typical drift orbit width of passing ions to the radial wavelength of the zonal flow increases.

SPECTOR3D is a magnetohydrodynamic (MHD) code designed to study the resistive stability and mode spectrum of stellarators. It finds the spectrum of the linearized, compressible, resistive MHD equations. Some typical results are given for a tokamak model with toroidal field ripple and a 17-period Heliotron.

The adaptive nonlinear filtering approach for shock/turbulence gas dynamics and magnetohydrodynamics (MHD) flows adopted in our previous work is employed in conjunction with compact high-order methods as the spatial base scheme. The objective is to compare the performance of nonlinear filtering in compact high-order schemes with nonlinear filtering in standard central (non-compact) schemes for multiscale problems containing shock waves.

We have developed a glassless stereoscopic visualization system for the real-time numerical simulator of the interplanetary space–magnetosphere– ionosphere coupling system, adopting the three-dimensional (3D) magnetohydrodynamical (MHD) simulation code. Our real-time Earth's magnetosphere simulator numerically reproduces the global response of the magnetosphere and the ionosphere at the same time with the real world by using the real-time Solar wind data, and has shown two-dimensional (2D) figures of the global magnetosphere of about 1 hour in advance in virtual reality at every minute on Web since November 2003. We implemented 3D graphical techniques such as volume and iso-surface rendering for visualizing scalar variables and also colored 3D streamlines for representing the magnetic field for standard and glassless stereo-displays. A real-time interpolation method mapping the simulated data to structured uniform rectilinear grids commonly utilized in computer graphics was developed, so that this 3D visualization system is capable of monitoring the real-time Earth's magnetosphere simulated data in on-line mode.

We have developed a parallel rendering software for scientific visualization of large-scale, three-dimensional, time development simulations. The goal of this software, MovieMaker, is to generate a movie, or a series of visualization images from one terabyte-scale data set within one night (or less than 12 h). The isocontouring, volume rendering, and streamlines are implemented. MovieMaker is a parallel program for the shared memory architecture with dynamic load balancing and overlapped disk I/O.

A parallel three-dimensional electrostatic particle-in-cell Monte Carlo Collision (PIC–MCC) code using an unstructured tetrahedral mesh is developed and validated in this paper. Poisson's equation is discretized by a nodal finite element method using a linear interpolation function. Charged-particle motion is traced cell by cell using a leap-frog method and the Boris scheme. Code is validated using quasi-one-dimensional radiofrequency gas discharge by observing the bi-Maxwellian electron energy probability distribution function at low pressure. Parallel performance of the PIC code is tested using a three-dimensional radiofrequency gas discharge on a PC-cluster system. Results show that parallel efficiency of 83% can be achieved at 32 processors with dynamic domain decomposition.

The classical Pierce model consists of a one-dimensional plasma-filled diode into which a monoenergetic electron beam is injected. Particle-in-cell (PIC) simulations are performed with the BIT1 code, involving a large number of superparticles. The evolution of slightly perturbed uniform equilibria into the related nonlinear attractor states for a broad range of $\alpha$ values, where $\alpha\,=\,\omega_{{\rm pe}}d/u_0$ is the diode control parameter, is investigated. A period-doubling route to chaos in the classical Pierce diode for $\alpha$ slightly below $5\pi$ is analyzed in detail.

Particle-in-cell simulations with full dynamics ions and drift kinetic electrons are essential tools to model kinetic instabilities in strongly magnetized plasmas. In these guiding center models, parallel acceleration of the electrons is retained while their perpendicular velocity is given to lowest order by the ${\bf E} \times{\bf B}$ drift. These simulations are applied to a study of the electrostatic stability of energetic velocity-space ion shells observed in the Earth's plasma sheet boundary layer by the Cluster satellites.

We study numerically the role of mode coupling mechanisms in the generation and growth of sideband modes, during the long time evolution of the nonlinear Landau damping of a large-amplitude wave. The results suggest that a rich variety of wave coupling mechanisms develops during the evolution of the system.

The characteristic features of a two-sign point vortex system in positive and negative temperature states are examined by massive numerical simulations using MDGRAPE-2. The temperature is determined by a density of states for a microcanonical ensemble consisting of randomly generated $10^7$ states. Since the density of states has a single peak, the system has negative temperature states. The distributions of vortices in time-asymptotic equilibrium states in positive and negative temperature are obtained by time-development simulations. In positive temperature, both-sign vortices mix with each other and neutralize. In negative temperature, part of the vortices condense and form clumps exclusively consisting of the same-sign vortices, while the other part of the vortices distribute uniformly outside the clumps. It is found that the vortices inside the clumps gain energy and the vortices outside the clumps lose energy to keep the total energy constant. This suggests the common and essential role of the background vortices in the energy-conserving system that assists the formation of the clumps as well as the crystallization and generation of the symmetric configuration observed in the non-neutral plasma experiments.