The advent of ultraintense laser pulses generated by the technique of chirped pulse amplification (CPA) along with the development of high-fluence laser materials has opened up an entirely new field of optics. The electromagnetic field intensities produced by these techniques, in excess of ${10}^{18}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$, lead to relativistic electron motion in the laser field. The CPA method is reviewed and the future growth of laser technique is discussed, including the prospect of generating the ultimate power of a zettawatt. A number of consequences of relativistic-strength optical fields are surveyed. In contrast to the nonrelativistic regime, these laser fields are capable of moving matter more effectively, including motion in the direction of laser propagation. One of the consequences of this is wakefield generation, a relativistic version of optical rectification, in which longitudinal field effects could be as large as the transverse ones. In addition to this, other effects may occur, including relativistic focusing, relativistic transparency, nonlinear modulation and multiple harmonic generation, and strong coupling to matter and other fields (such as high-frequency radiation). A proper utilization of these phenomena and effects leads to the new technology of relativistic engineering, in which light-matter interactions in the relativistic regime drives the development of laser-driven accelerator science. A number of significant applications are reviewed, including the fast ignition of an inertially confined fusion target by short-pulsed laser energy and potential sources of energetic particles (electrons, protons, other ions, positrons, pions, etc.). The coupling of an intense laser field to matter also has implications for the study of the highest energies in astrophysics, such as ultrahigh-energy cosmic rays, with energies in excess of ${10}^{20}\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The laser fields can be so intense as to make the accelerating field large enough for general relativistic effects (via the equivalence principle) to be examined in the laboratory. It will also enable one to access the nonlinear regime of quantum electrodynamics, where the effects of radiative damping are no longer negligible. Furthermore, when the fields are close to the Schwinger value, the vacuum can behave like a nonlinear medium in much the same way as ordinary dielectric matter expanded to laser radiation in the early days of laser research.

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Optics in the relativistic regime

http://absimage.aps.org/image/DAMOP12/MWS_DAMOP12-2012-000066.pdf

Optics in the Relativistic Regime

Collisionless electron-temperature-gradient-driven (ETG) turbulence in toroidal geometry is studied via nonlinear numerical simulations To this aim, two massively parallel, fully gyrokinetic Vlasov codes are used, both including electromagnetic effects Somewhat surprisingly, and unlike in the analogous case of ion-temperature-gradient-driven (ITG) turbulence, we find that the turbulent electron heat flux is significantly underpredicted by simple mixing length estimates in a certain parameter regime (ŝ∼1, low α) This observation is directly linked to the presence of radially highly elongated vortices (“streamers”) which lead to very effective cross-field transport The simulations therefore indicate that ETG turbulence is likely to be relevant to magnetic confinement fusion experiments

Electron temperature gradient driven turbulence

There is a wide range of fundamental physical problems directly related to how pulsars function. Some of these are independent of the specific pulsar mechanism. Others relate directly to the physics of the pulsar and already shed some light on the properties of matter at high density (\ensuremath{\sim}${10}^{15}$ g/cc) and in strong magnetic fields (\ensuremath{\sim}${10}^{12}$ G). Pulsars are assumed to be rotating neutron stars surrounded by strong magnetic fields and energetic particles. It is somewhere within this "magnetosphere" that the pulsar action is expected to take place. Currently there has been considerable difficulty in formulating an entirely self-consistent theory of the magnetospheric behavior and there may be rapid revisions in the near future, which is all the more surprising since many of the issues involve "elementary" problems in electromagnetism. One interesting discovery is that charge-separated plasmas apparently can support stable static discontinuities.

Theory of pulsar magnetospheres

This article has dealt with various aspects of parabolic approximation methods in underwater acoustics, mostly for propagation of sinusoidal signals Extensions of these methods to time-dependent problems are also available: pulse propagation, moving sources and receivers, frequency shifting effects due to rapid temporal variations of oceanic conditions, and so forth However, an adequate description of these extensions would require another long section and it was felt that the principles involved in making parabolic approximations have been sufficiently illustrated Parabolic equation methods in underwater acoustics were developed only in the last few years, and as more and more use is made of these methods we may expect that many of the important modelling problems in ocean acoustics may be solved

The parabolic approximation method

The interaction between charged particles and sharply localized fields is investigated. The random particle scattering is described by a Fokker-Planck equation whose time-dependent solution exhibits the formation of a highly populated superthermal tail.

Effect of localized electric fields on the evolution of the velocity distribution function

The evolution of a single tearing mode is investigated. The ''collisionless'' and ''collisional'' tearing modes nonlinearly evolve into the ''semicollisional'' regime where the dynamics of the ''singular layer'' are dominated by electron along the perturbed magnetic surfaces. The ''semicollisional'' mode grows algebraically in the nonlinear phase as in the ''collisional'' calculation of Rutherford.

Nonlinear Evolution of Collisionless and Semicollisional Tearing Modes

The nonlinear distortion of the propagation cones of lower-hybrid waves is shown to be governed by the modified Korteweg-de Vries equation. Since such an equation admits exact solutions of the multiple-soliton form, it is predicted that filamented cones sould be formed when large-amplitude lower-hybrid waves are excited in a plasma.

Nonlinear Filamentation of Lower-Hybrid Cones

The effect of the ponderomotive force in the interaction of a capacitor rf field with a nonuniform plasma is investigated.

Ponderomotive-Force Effects in a Nonuniform Plasma

We derive the equations describing the decay of an intense, coherent electromagnetic wave into a backscattered electromagnetic wave and a plasma wave in an inhomogeneous plasma. The plasma wave and scattered electromagnetic wave are trapped in the vicinity of their cutoffs near ${\ensuremath{\omega}}_{p}=\frac{{\ensuremath{\omega}}_{0}}{2}$. The resulting temporally growing instabilities may explain the strong heating and the blowoff observed in recent computer simulations of Raman scattering.

Y. C. Lee

Papers

Effect of localized electric fields on the evolution of the velocity distribution function

Nonlinear Evolution of Collisionless and Semicollisional Tearing Modes

Nonlinear Filamentation of Lower-Hybrid Cones

Ponderomotive-Force Effects in a Nonuniform Plasma

Temporally growing Raman backscattering instabilities in an inhomogeneous plasma