Nonlinear electromagnetic phenomena in the relativistic interaction of ultrahigh intensity laser pulses with plasmas

2D, low-frequency, relativistic solitary waves have been found recently in 2D. Particle-in-cell simulations of ultra-intense laser pulses propagating in underdense plasmas, in regimes where the laser pulse undergoes energy depletion and downshifting of its frequency. These slowly propagating, spatially localized, electromagnetic structures represent an important channel of energy conversion from the laser pulse to the plasma. Pulse energy can also be converted into fast propagating structures, associated with collimated beams of ultrarelativistic electrons. Lienard-Wiechert magnetic field structures have been observed in PIC simulations to move together with focalized ultrarelativistic electron beams in the plasma

Ion acceleration regimes in underdense plasmas

Acceleration of large populations of ions up to high (relativistic) energies may represent one of the most important and interesting tools that can be provided by the interaction of petawatt laser pulses with matter. In this paper, the basic mechanisms of ion acceleration by short laser pulses are studied in underdense plasmas. The ion acceleration does not originate directly from the pulse fields, but it is mediated by the electrons in the form of electrostatic fields originating from channeling, double layer formation, and Coulomb explosion

Interaction of petawatt laser pulses with underdense plasmas

Results are presented from analytical study and particle-in-cell simulations of the interaction of ultrashort petawatt laser pulses with underdense plasmas. It is shown that this interaction exhibits effects typical of the interaction of moderate-power pulses with overdense plasmas. The results obtained demonstrate relativistic self-focusing, the formation of a vacuum channel in a plasma, excitation of a superstrong longitudinal electric field, acceleration of ions and electrons up to ultrarelativistic energies, and generation of a quasistatic magnetic field. The generation of relativistic electromagnetic solitons is demonstrated. It is shown that a significant part of the laser-pulse energy is transformed into the energy of these solitons. The space and time dependences of the fields inside the solitons are found to agree with our analytical description

Laser acceleration of charged particles in inhomogeneous plasmas II: Particle injection into the acceleration phase due to nonlinear wake wave-breaking

Results from analytical studies and computer simulations of the nonlinear evolution of wake waves in inhomogeneous plasmas are presented. It is shown that the wake wave-breaking that appears due to the inhomogeneity of the Langmuir frequency can be used to inject electrons into the acceleration phase of the wave. In the wake wave excited behind a finite-width laser pulse, the wave-breaking mechanism involves the increase in the curvature of the wake front with the distance from the pulse, followed by the self-intersection of the electron trajectories

Coherent electromagnetic structures in relativistic plasmas

Relativistic electromagnetic low-frequency solitary waves are found to occur in underdense plasmas in regimes where the laser pulse becomes filamented and undergoes energy depletion and frequency downshifting. These slowly propagating "subcycle-solitons" represent one of the channels of conversion of the laser pulse energy. Electron vortices and their associated quasistatic magnetic field represent a different important type of long lived coherent electromagnetic structures. Their generation is related to the dynamics of fast electron currents in the plasma

High density collimated beams of relativistic ions produced by petawatt laser pulses in plasmas

Under optimal interaction conditions ions can be accelerated up to relativistic energies by a petawatt laser pulse in both underdense and overdense plasmas. Two-dimensional particle in cell simulations show that the laser pulse drills a channel through an underdense plasma slab due to relativistic self-focusing. Both ions and electrons are accelerated in the head region of the channel. However, ion acceleration is more effective at the end of the slab. Here electrons from the channel expand in vacuum and are followed by the ions dragged by the Coulomb force arising from charge separation. A similar mechanism of ion acceleration occurs when a superintense laser pulse interacts with a thin slab of overdense plasma and the pulse ponderomotive pressure moves all the electrons away from a finite-diameter spot

Generation of collimated beams of relativistic ions in laser-plasma interactions

A method is proposed for generating collimated beams of fast ions in laser-plasma interactions. Two-dimensional and three-dimensional particle-in-cell simulations show that the ponderomotive force expels electrons from the plasma region irradiated by a laser pulse. The ions with unneutralized electric charge that remain in this region are accelerated by Coulomb repulsive forces. The ions are focused by tailoring the target and also as a result of pinching in the magnetic field produced by the electric current of fast ions. (C) 2000 MAIK "Nauka/Interperiodica"

Ion acceleration by superintense laser pulses in plasmas

Ion acceleration by petawatt laser radiation in underdense and overdense plasmas is studied with 2D3V-PIC (Particle in Cell) numerical simulations. These simulations show that the laser pulse drills a channel through the plasma slab, and electrons and ions expand in vacuum. Fast electrons escape first from the electron-ion cloud. Later, ions gain a high energy on account of the Coulomb explosion of the cloud and the inductive electric field which appears due to fast change of the magnetic field generated by the laser pulse. Similarly, when a superintense laser pulse interacts with a thin slab of overdense plasma, its ponderomotive pressure blows all the electrons away from a finite-diameter spot on the slab. Then, due to the Coulomb explosion, ions gain an energy as high as 1 GeV. (C) 1999 American Institute of Physics. [S0021-3640(99)00414-4]

Reconnection of magnetic field lines near critical points

A review of theoretical studies and computer simulations of the plasma dynamics near critical points of the magnetic field is presented. The global characteristics of reconnection of the magnetic field lines and vortex lines are discussed. Examples of typical patterns of the magnetic field near critical points are presented. The propagation of MHD waves and the formation of singularities near null lines and separatrix surfaces are discussed. Nonlinear regimes of the plasma dynamics are described, and exact solutions of the MHD equations in which the Hall effect is taken into account are presented. The magnetic reconnection in the frame of the electron magnetohydrodynamics model is also discussed. The results of computer simulations of the current sheet formation near null lines and separatrices of the magnetic field are presented. The nonadiabatic motion and the acceleration of charged particles near critical points are discussed