M.Yu. Romanovsky

Dynamics of an electron driven by relativistically intense laser radiation

The dynamics of an electron driven by a relativistically intense laser pulse is analyzed on the basis of the equation of motion with the Lorentz force in the cases of linear and circular polarizations. Laser fields with nonplane phase fronts accelerate electrons in the longitudinal direction. An electron initially at rest is found not to move along figure-eight trajectories for the linear polarization, and not to move along circular trajectories for the circular polarization.

Electrodynamics of electron in a superintense laser field: New principles of diagnostics of relativistic laser intensity

The dynamics and energy spectra of electrons driven by a relativistically intense laser pulse are analyzed. The description is based on the numerical solution of the relativistic Newton’s equation with the Lorentz force generated by a strong focused optical field. After the interaction with it, electrons retain a considerable fraction of the energy of their oscillations during the interaction. The electron postinteraction energy spectrum is calculated. The energies in the spectrum high-energy tail are determined by the laser pulse intensity at the focal spot. An approach to estimating absolute values of the laser pulse intensity based on the measurement of the energy spectra of the electrons is proposed.

Functional Lévy walks

The problem of finding the probability distribution function for a random variable which is the function of a random walking radius vector is analyzed. It is shown for a wide class of these functions hyperbolically dependent on the value of the radius vector that the probability density distributions of these random variables are the known Lévy functions. The conditions under which functional Lévy walks pass into truncated ones are considered.

Analytical Representations of Non-Gaussian Laws of Random Walks

An analytical representation of a random process with independent increments in some space (random walks introduced by Pearson) is considered. The law of random walk distribution in space is derived from the general representation of stochastic elementary hops (distribution law of hop probability) using Kadanoff’s concept of the unit increment as one hop. For limited hop laws and laws of hop distributions with all moments there naturally arises Chandrasekhar’s result that describes ordinary physical diffusion. For laws of hop distributions without the second and highest moments there also arise known Lévy walks (flights) sometimes treated as superdiffusion. For the intermediate case, where the distributions of hops have at least the second moment and not all finite moments (these hops are sometimes called truncated Lévy walks), the asymptotic form of the random walk distribution was obtained for the first time. The results obtained are compared with the experimental laws known in econophysics. Satisfactory agreement is observed between the developed theory and the empirical data for insufficiently studied truncated Lévy walks.

Corrections of electron impact ionization rates by plasmas electric microfield

Abstract The action of electric microfield in plasma “stochastics domains” on the ionization process due to electron–ion collisions is considered. It is shown that corrections to the ionization rate in plasmas arise mostly by changes of kinetic energy of impact electron due to the local electric microfield in the domain where the collision occurs.

Electron acceleration in quasi-stationary electromagnetic fields during the self-channeling of intense light pulses

We theoretically investigate the possibility of electron acceleration during the self-channeled propagation of laser radiation. We consider a new acceleration mechanism associated with the formation of an ion cloud in material (under the ponderomotive force of the laser radiation) that moves together with the laser pulse. We show that the quasi-stationary electric and magnetic fields generated by the moving ion cloud can lead to the acceleration of electrons up to energies of several dozen MeV and to the formation of an electron beam propagating forward coaxially with the laser pulse. The calculated angular distribution of the accelerated electrons is in satisfactory agreement with published experimental results.

Recoil ion momentum distributions from laser-induced double ionization

The momentum distribution of a doubly charged recoil ion is considered. On the basis of the semiclassical rescattering picture, we propose a model, allowing for basic studies and physical interpretations of the main properties of measured momentum distributions such as the position and the width of the observed double humps. Simple formulas are derived which agree rather well with several experimental findings.

Action of an electric microfield on ionization processes in laser-produced plasmas

Abstract The action of the electric microfield in plasmas on the ionization processes is considered. It is shown that the processes of tunnel and rescattering ionization by a laser field are strongly controlled by the electric microfield of plasmas.

Electric and magnetic microfields inside and outside space-limited configurations of ions and ionic currents

The problem of electric and magnetic microfields inside finite spherical systems of stochastically moving ions and outside them is studied. The first possible field of applications is high temperature ion clusters created by laser fields [1]. Other possible applications are nearly spherical liquid systems at room-temperature containing electrolytes. Looking for biological applications we may also think about a cell which is a complicated electrolytic system or even a brain which is a still more complicated system of electrolytic currents. The essential model assumption is the random character of charges motion. We assume in our basic model that we have a finite nearly spherical system of randomly moving charges. Even taking into account that this is at best a caricature of any real system, it might be of interest as a limiting case, which admits a full theoretical treatment. For symmetry reasons, a random configuration of moving charges cannot generate a macroscopic magnetic field, but there will be microscopic fluctuating magnetic fields. Distributions for electric and magnetic microfields inside and outside such space- limited systems are calculated. Spherical systems of randomly distributed moving charges are investigated. Starting from earlier results for infinitely large systems, which lead to Holtsmark- type distributions, we show that the fluctuations in finite charge distributions are larger (in comparison to infinite systems of the same charge density).

Response to 'Comment on 'Dynamics of an electron driven by relativistically intense laser radiation'' [Phys. Plasmas 17, 064701 (2010)]

In a recent comment, Tian et al. [Phys. Plasmas 17, 064701 (2010)] reported a disagreement between their simulation results for the dynamics of an electron in a circularly polarized relativistically intense laser field and those presented in this paper. We demonstrate that the disagreement stems from certain inaccuracies in the analysis and the numerical simulation of the electron dynamics in the comment.