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A new formulation based on Hamiltonian reduction technique using the invariance of generalized canonical momentum is introduced for the study of relativistic Weibel-type instability. An example of application is given for the current filamentation instability resulting from the propagation of two counter-streaming electron beams in the relativistic regime of the instability. This model presents a double advantage. From an analytical point of view, the method is exact and standard fluid dispersion relations for Weibel or filamentation instabilies can be recovered. From a numerical point of view, the method allows a drastic reduction of the computational time. A 1D multi-stream Vlasov-Maxwell code is developed using such dynamical invariants in the perpendicular momentum space. Numerical comparison with a full Vlasov-Maxwell system has also been carried out to show the efficiency of this reduction technique. [ABSTRACT FROM AUTHOR]

The interplay between the Kelvin-Helmholtz, the Rayleigh-Taylor and the Magnetic Re-connection instabilities in a magnetized inhomogeneous plasma with a sheared velocity field is investigated within the framework of a two-dimensional, two fluid model. This magnetic configuration is of interest for the investigation of the mixing process between the solar wind plasma and the Earth’s magnetospheric plasma at low latitudes at the magnetospheric flank. It is found that the combined role of the density inhomogeneity and of the in-plane magnetic field during the development of the Kelvin Helmholtz instability is multi faceted. It leads to small scale magnetic islands through the development of induced magnetic field line reconnection but at the same time the in-plane magnetic field preserves the global coherence of the vortex merging process (vortex pairing). [ABSTRACT FROM AUTHOR]

The role of the “generalized connections” in the development of collisionless magnetic field line reconnection and in the formation of current and vorticity layers is discussed in a two dimensional plasma configuration with a strong guide magnetic field. Secondary instabilities can modify how magnetic connections are advected in the plasma and lead to turbulent redistribution of the current layers and to the formation of long lived fluid vortices inside magnetic islands. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The observed core-halo structure of the electron distribution function (hereafter e.d.f.) in the solar wind can be interpreted in two ways. In the first type of interpretation, the core adjusts adiabatically to the local solar wind conditions while the suprathermal particles result from the collisionless expansion of the coronal plasma. The second interpretation is fully local, the halo electrons resulting from the wave particle interactions, as observed in practically all low density collisionless plasmas. In this work we explore this last interpretation using numerical simulations of the Vlasov — Poisson equations. We propose that the source of the waves able to interact with the thermal electrons is to be found in the cascade from large scale, fluid fluctuations towards small, kinetic scales. In our approach we use a low frequency, random force acting on the protons to represent the effect of the fluid cascade and a high frequency, random force to excite a level of plasma waves modeling the effects of the thermal noise. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Some recent developments in the analytical and numerical study of the interaction of ultra-intense ultra-short laser pulses with relativistic plasmas are reviewed. Special attention is given to the subject of ion acceleration in view of its applications which range from proton imaging to the acceleration of collimated ion bunches and to the effect of fast magnetic field line reconnection on the evolution of the self-generated magnetic field. [ABSTRACT FROM AUTHOR]

Low frequency, relativistic sub-cycle localised (soliton-like) concentrations of the electromagnetic (em) energy are found in two-dimensional (2D) and in three-dimensional (3D) Particle in Cell simulations of the interaction of ultra-short, high-intensity laser pulses with homogeneous and inhomogeneous plasmas. These solitons consist of electron and ion density depressions and intense em field concentrations with a frequency definitely lower than that of the laser pulse. The downshift of the pulse frequency, due to the depletion of the pulse energy, causes a significant portion of the pulse em energy to become trapped as solitons, slowly propagating inside the plasma. In an earlier phase solitons are formed due to the trapping of the em radiation inside an electron cavity, while ions can be assumed to remain at rest. Later on, after (m[SUBi]/m[SUBi])[SUP1/2] times the laser period, ions start to move and the ion depletion occurs producing a slowly growing hole in the plasma density. In inhomogeneous plasmas the solitons are accelerated toward the plasma vacuum interface where they radiate away their energy in the form of bursts of low frequency em radiation. In the frame of a 1D cold hydrodynamic model for an electron-ion plasma, the existence of multipeaked em solitons has been investigated both analytically and numerically. The analytical expression for a sub-cycle relativistic soliton has been derived for circularly polarized pulses in a cold isotropic plasma, and in the presence of an externally applied magnetic field. Recently, em relativistic solitons in a hot multi-component plasma have been investigated in the frame of an hydrodynamic (adiabatic) model and of a kinetic (isothermal) model. An overview of the most recent analytical and numerical results on the soliton dynamics is given. [ABSTRACT FROM AUTHOR]

The dynamics and generation of surface structures in intense laser interaction with overdense plasmas is studied numerically and analytically. The dynamics of two-dimensional (2D) electron surface oscillations (ESOs) has been resolved in particle-in-cell simulations, showing a “period doubling” effect with respect to the driving magnetic force of the laser. A new parametric process, in which a 1D electrostatic oscillation decays into two electromagnetic surface waves, has been investigated analytically and provides a mechanism for the generation of ESOs. For oblique laser incidence and p-polarization generation of subharmonic surface waves is also predicted. The possible impact of surface deformations on fast electron generation and disruption of plasma “moving mirrors” for high harmonic generation is discussed. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetic field generated by the Electro-Magnetic Current Filamentation Instability (EMCFI) is shown to develop magnetic islands due to the onset of a fast reconnection instability that occurs on the electron time scale. The main source of free energy for both instabilities is essentially the initial anisotropy of the two counterstreaming electron populations. Numerical results of a 2D-3V Vlasov code are presented and interpreted in terms of the theory of collisionless reconnection in the whistler regime in an anisotropic plasma. These results are relevant to the process of magnetic channel coalescence in relativistic laser plasma interactions and confirm the dynamical role of the magnetic field generated in the wake of the laser pulse first remarked in Ref. [1]. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]