614 research outputs found
Single-Cycle High-Intensity Electromagnetic Pulse Generation in the Interaction of a Plasma Wakefield with Nonlinear Coherent Structures
The interaction of coherent nonlinear structures (such as sub-cycle solitons,
electron vortices and wake Langmuir waves) with a strong wake wave in a
collisionless plasma can be exploited in order to produce ultra-short
electromagnetic pulses. The electromagnetic field of a coherent nonlinear
structure is partially reflected by the electron density modulations of the
incident wake wave and a single-cycle high-intensity electromagnetic pulse is
formed. Due to the Doppler effect the length of this pulse is much shorter than
that of the coherent nonlinear structure. This process is illustrated with
two-dimensional Particle-in-Cell simulations. The considered laser-plasma
interaction regimes can be achieved in present day experiments and can be used
for plasma diagnostics.Comment: 11 pages, 11 figures. Submitted to Phys. Rev.
Dynamics of relativistic solitons
Relativistic solitons are self-trapped, finite size, electromagnetic waves of
relativistic intensity that propagate without diffraction spreading. They have
been predicted theoretically within the relativistic fluid approximation, and
have been observed in multi-dimensional particle in cell simulations of laser
pulse interaction with the plasma. Solitons were observed in the laser
irradiated plasmas with the proton imaging technique as well. This paper
reviews many theoretical results on relativistic solitons in electron-ion
plasmas.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Three Dimensional Relativistic Electromagnetic Sub-cycle Solitons
Three dimensional (3D) relativistic electromagnetic sub-cycle solitons were
observed in 3D Particle-in-Cell simulations of an intense short laser pulse
propagation in an underdense plasma. Their structure resembles that of an
oscillating electric dipole with a poloidal electric field and a toroidal
magnetic field that oscillate in-phase with the electron density with frequency
below the Langmuir frequency. On the ion time scale the soliton undergoes a
Coulomb explosion of its core, resulting in ion acceleration, and then evolves
into a slowly expanding quasi-neutral cavity.Comment: 5 pages, 6 figures;
http://www.ile.osaka-u.ac.jp/research/TSI/Timur/soliton/index.htm
Scaling laws of resistive magnetohydrodynamic reconnection in the high-Lundquist-number, plasmoid-unstable regime
The Sweet-Parker layer in a system that exceeds a critical value of the
Lundquist number () is unstable to the plasmoid instability. In this paper,
a numerical scaling study has been done with an island coalescing system driven
by a low level of random noise. In the early stage, a primary Sweet-Parker
layer forms between the two coalescing islands. The primary Sweet-Parker layer
breaks into multiple plasmoids and even thinner current sheets through multiple
levels of cascading if the Lundquist number is greater than a critical value
. As a result of the plasmoid instability, the system
realizes a fast nonlinear reconnection rate that is nearly independent of ,
and is only weakly dependent on the level of noise. The number of plasmoids in
the linear regime is found to scales as , as predicted by an earlier
asymptotic analysis (Loureiro \emph{et al.}, Phys. Plasmas \textbf{14}, 100703
(2007)). In the nonlinear regime, the number of plasmoids follows a steeper
scaling, and is proportional to . The thickness and length of current sheets
are found to scale as , and the local current densities of current
sheets scale as . Heuristic arguments are given in support of theses
scaling relations.Comment: Submitted to Phys. Plasma
Review of analytical instruments for EEG analysis
Since it was first used in 1926, EEG has been one of the most useful
instruments of neuroscience. In order to start using EEG data we need not only
EEG apparatus, but also some analytical tools and skills to understand what our
data mean. This article describes several classical analytical tools and also
new one which appeared only several years ago. We hope it will be useful for
those researchers who have only started working in the field of cognitive EEG
Radiation Pressure Dominate Regime of Relativistic Ion Acceleration
The electromagnetic radiation pressure becomes dominant in the interaction of
the ultra-intense electromagnetic wave with a solid material, thus the wave
energy can be transformed efficiently into the energy of ions representing the
material and the high density ultra-short relativistic ion beam is generated.
This regime can be seen even with present-day technology, when an exawatt laser
will be built. As an application, we suggest the laser-driven heavy ion
collider.Comment: 10 pages, 4 figure
Lorentz-Abraham-Dirac vs Landau-Lifshitz radiation friction force in the ultrarelativistic electron interaction with electromagnetic wave (exact solutions)
When the parameters of electron - extreme power laser interaction enter the
regime of dominated radiation reaction, the electron dynamics changes
qualitatively. The adequate theoretical description of this regime becomes
crutially important with the use of the radiation friction force either in the
Lorentz-Abraham-Dirac form, which possess unphysical runaway solutions, or in
the Landau-Lifshitz form, which is a perturbation valid for relatively low
electromagnetic wave amplitude. The goal of the present paper is to find the
limits of the Landau-Lifshitz radiation force applicability in terms of the
electromagnetic wave amplitude and frequency. For this a class of the exact
solutions to the nonlinear problems of charged particle motion in the
time-varying electromagnetic field is used.Comment: 14 pages, 5 figure
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