I. Y. Dodin

Langmuir wave linear evolution in inhomogeneous nonstationary anisotropic plasma

A hydrodynamic equation describing the linear evolution of a nondissipative Langmuir wave in inhomogeneous nonstationary anisotropic plasma without magnetic field is derived in the geometrical optics approximation. The continuity equation for the wave action density, anticipated from general principles, is then confirmed ab initio, and the conditions for the action conservation are formulated. Given those, the wave field E universally scales with the electron density N as E∝N3/4 in homogeneous plasma, whereas the wavevector evolution varies depending on the wave geometry.A hydrodynamic equation describing the linear evolution of a nondissipative Langmuir wave in inhomogeneous nonstationary anisotropic plasma without magnetic field is derived in the geometrical optics approximation. The continuity equation for the wave action density, anticipated from general principles, is then confirmed ab initio, and the conditions for the action conservation are formulated. Given those, the wave field E universally scales with the electron density N as E∝N3/4 in homogeneous plasma, whereas the wavevector evolution varies depending on the wave geometry.

Axiomatic Geometrical Optics, Abraham-Minkowski Controversy, and Photon Properties Derived Classically

By restating geometrical optics within the eld-theoretical approach, the classical concept of a photon in arbitrary dispersive medium is introduced, and photon properties are calculated unambiguously. In particular, the canonical and kinetic momenta carried by a photon, as well as the two corresponding energy-momentum tensors of a wave, are derived straightforwardly from rst principles of Lagrangian mechanics. The Abraham-Minkowski controversy pertaining to the de nitions of these quantities is thereby resolved for linear waves of arbitrary nature, and corrections to the traditional formulas for the photon kinetic quantities are found. An application of axiomatic geometrical optics to electromagnetic waves is also presented as an example.

Ponderomotive barrier as a Maxwell demon

The possibility of efficient ponderomotive current drive in a magnetized plasma was reported recently in [N. J. Fisch, J. M. Rax, and I. Y. Dodin, Phys. Rev. Lett. 91, 205004 (2003)]. Precise limitations on the efficiency are now given through a comprehensive analytical and numerical study of single-particle dynamics under the action of a cyclotron-resonant rf drive in various field configurations. Expressions for the particle energy gain and acceleration along the dc magnetic field are obtained. The fundamental correlation between the two effects is described. A second fundamental quantity, namely, the ratio of the potential barrier to the energy gain, can be changed by altering the field configuration. The asymmetric ponderomotive current drive effect can be optimized, by minimizing the transverse heating.

Amplification of short laser pulses by Raman backscattering in capillary plasmas

Short laser pulses can be significantly amplified in the process of Raman backscattering in plasma inside an oversized dielectric capillary. A dielectric capillary allows obtaining high intensities of the output radiation by sustaining efficient amplification at large distances compared to the diffraction length. The efficiency of the interaction between the pump wave and the amplified pulse is shown not to be critically sensitive to the transverse structure of the wave fields. For a quasi-single-mode initial seed pulse and a low pump intensity, the amplified pulse tends to preserve its transverse structure due to nonlinear competition of the capillary eigen-modes. At a high power of the pump wave, multimode amplification always takes place but the growth of the front peak of the pulse still follows the one-dimensional model. The Raman backscattering instability of the pump wave resulting in the noise amplification can be suppressed in detuned interaction by chirping the pump wave or arranging an inhomogeneous plasma density profile along the trace of amplification. The efficiency of the desired pulse amplification does not significantly depend on detuning in the case of a smooth detuning profile. Density inhomogeneities are shown to exert less influence on the amplification within a capillary than in the one-dimensional problem. Parameters of a future experiment on the Raman amplification of a short laser pulse inside a capillary are proposed.

On Variational Methods In the Physics of Plasma Waves

Abstract A first-principle variational approach to adiabatic collisionless plasma waves is described. The focus is made on one-dimensional electrostatic oscillations, including phase-mixed electron plasma waves (EPWs) with trapped particles, such as Bernstein-Greene-Kruskal modes. Whitham’s theory is extended by an explicit calculation of the EPW Lagrangian, which is related to the oscillation-center energies of individual particles in a periodic field, and those are found by a quadrature. Some paradigmatic physics of EPWs is discussed for illustration purposes.

Adiabatic nonlinear waves with trapped particles. I. General formalism

A Lagrangian formalism is developed for a general nondissipative quasiperiodic nonlinear wave with trapped particles in collisionless plasma. The adiabatic time-averaged Lagrangian density

Positive and negative effective mass of classical particles in oscillatory and static fields.

\mcc{L}

Adiabatic nonlinear waves with trapped particles. II. Wave dispersion

is expressed in terms of the single-particle oscillation-center Hamiltonians; once those are found, the complete set of geometrical-optics equations is derived without referring to the Maxwell-Vlasov system. The number of trapped particles is assumed fixed; in particular, those may reside close to the bottom of the wave trapping potential, so they never become untrapped. Then their contributions to the wave momentum and the energy flux depend mainly on the trapped-particle density, as an independent parameter, and the phase velocity rather than on the wave amplitude

Nonlinear Dispersion of Stationary Waves in Collisionless Plasmas

a

Adiabatic nonlinear waves with trapped particles. III. Wave dynamics

explicitly; hence,