scholarly journals Particle-in-cell simulations of electron acceleration by a simple capacitative antenna in collisionless plasma

2004 ◽  
Vol 109 (A12) ◽  
Author(s):  
M. E. Dieckmann
Keyword(s):  
Collisionless Plasma ◽  
Electron Acceleration ◽  
Particle In Cell

Power spectral density of magnetic field and ion velocity fluctuations from inertial to kinetic ranges

2021 ◽  
Author(s):  
Jana Šafránková ◽  
Zdeněk Němeček ◽  
František Němec ◽  
Luca Franci ◽  
Alexander Pitňa
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Collisionless Plasma ◽  
Power Spectra ◽  
Physical Parameters ◽  
Particle In Cell ◽  
High Reynolds ◽  
Experimental Findings ◽  
Turbulent Cascade

<p>The solar wind is a unique laboratory to study the turbulent processes occurring in a collisionless plasma with high Reynolds numbers. A turbulent cascade—the process that transfers the free energy contained within the large scale fluctuations into the smaller ones—is believed to be one of the most important mechanisms responsible for heating of the solar corona and solar wind. The paper analyzes power spectra of solar wind velocity, density and magnetic field fluctuations that are computed in the frequency range around the break between inertial and kinetic scales. The study uses measurements of the Bright Monitor of the Solar Wind (BMSW) on board the Spektr-R spacecraft with a time resolution of 32 ms complemented with 10 Hz magnetic field observations from the Wind spacecraft propagated to the Spektr-R location. The statistics based on more than 42,000 individual spectra show that: (1) the spectra of both quantities can be fitted by two (three in the case of the density) power-law segments; (2) the median slopes of parallel and perpendicular fluctuation velocity and magnetic field components are different; (3) the break between MHD and kinetic scales as well as the slopes are mainly controlled by the ion beta parameter. These experimental results are compared with high-resolution 2D hybrid particle-in-cell simulations, where the electrons are considered to be a massless, charge-neutralizing fluid with a constant temperature, whereas the ions are described as macroparticles representing portions of their distribution function. In spite of several limitations (lack of the electron kinetics, lower dimensionality), the model results agree well with the experimental findings. Finally, we discuss differences between observations and simulations in relation to the role of important physical parameters in determining the properties of the turbulent cascade.</p>

scholarly journals Structure of a collisionless pair jet in a magnetized electron–proton plasma: flow-aligned magnetic field

2019 ◽  
Vol 621 ◽  
pp. A142 ◽  
Author(s):  
M. E. Dieckmann ◽  
D. Folini ◽  
I. Hotz ◽  
A. Nordman ◽  
P. Dell’Acqua ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Collisionless Plasma ◽  
Mean Velocity ◽  
Ambient Plasma ◽  
Particle In Cell ◽  
Flow Energy ◽  
Pair Plasma ◽  
Background Magnetic Field ◽  
Order Of Magnitude ◽  
Uniform Background

Aims. We study the effect a guiding magnetic field has on the formation and structure of a pair jet that propagates through a collisionless electron–proton plasma at rest. Methods. We model with a particle-in-cell (PIC) simulation a pair cloud with a temperature of 400 keV and a mean speed of 0.9c (c - light speed). Pair particles are continuously injected at the boundary. The cloud propagates through a spatially uniform, magnetized, and cool ambient electron–proton plasma at rest. The mean velocity vector of the pair cloud is aligned with the uniform background magnetic field. The pair cloud has a lateral extent of a few ion skin depths. Results. A jet forms in time. Its outer cocoon consists of jet-accelerated ambient plasma and is separated from the inner cocoon by an electromagnetic piston with a thickness that is comparable to the local thermal gyroradius of jet particles. The inner cocoon consists of pair plasma, which lost its directed flow energy while it swept out the background magnetic field and compressed it into the electromagnetic piston. A beam of electrons and positrons moves along the jet spine at its initial speed. Its electrons are slowed down and some positrons are accelerated as they cross the head of the jet. The latter escape upstream along the magnetic field, which yields an excess of megaelectronvolt positrons ahead of the jet. A filamentation instability between positrons and protons accelerates some of the protons, which were located behind the electromagnetic piston at the time it formed, to megaelectronvolt energies. Conclusions. A microscopic pair jet in collisionless plasma has a structure that is similar to that predicted by a hydrodynamic model of relativistic astrophysical pair jets. It is a source of megaelectronvolt positrons. An electromagnetic piston acts as the contact discontinuity between the inner and outer cocoons. It would form on subsecond timescales in a plasma with a density that is comparable to that of the interstellar medium in the rest frame of the latter. A supercritical fast magnetosonic shock will form between the pristine ambient plasma and the jet-accelerated plasma on a timescale that exceeds our simulation time by an order of magnitude.

scholarly journals Electron acceleration in underdense plasmas described with a classical effective theory

2015 ◽  
Vol 33 (2) ◽  
pp. 307-313 ◽  
Author(s):  
M. A. Pocsai ◽  
S. Varró ◽  
I. F. Barna
Keyword(s):  
Experimental Data ◽  
Continuous Medium ◽  
Equations Of Motion ◽  
Electron Acceleration ◽  
Index Of Refraction ◽  
Effective Theory ◽  
Electron Motion ◽  
Particle In Cell ◽  
Underdense Plasmas ◽  
Relativistic Equations

AbstractAn effective theory of laser–plasma-based particle acceleration is presented. Here we treated the plasma as a continuous medium with an index of refraction nm in which a single electron propagates. Because of the simplicity of this model, we did not perform particle-in-cell (PIC) simulations in order to study the properties of the electron acceleration. We studied the properties of the electron motion due to the Lorentz force and the relativistic equations of motion were numerically solved and analyzed. We compared our results with PIC simulations and experimental data.

scholarly journals Phase space structures generated by absorbing obstacles in streaming plasmas

2005 ◽  
Vol 23 (3) ◽  
pp. 853-865 ◽  
Author(s):  
P. Guio ◽  
H. L. Pécseli
Keyword(s):  
Phase Space ◽  
Collisionless Plasma ◽  
Flow Characteristics ◽  
Plasma Potential ◽  
Velocity Shear ◽  
Space Structures ◽  
Space Plasmas ◽  
Physical Parameters ◽  
Particle In Cell ◽  
Cell Simulation

Abstract. The dynamic behavior of a collisionless plasma flowing around an obstacle is investigated by numerical methods. In the present studies, the obstacle is formed by an absorbing cylinder, and a 2-D electrostatic particle-in-cell simulation is used to study the flow characteristics, with extensions to a fully 3-D generalization of the problem demonstrated as well. The formation of irregular filamented density depletions, oblique to the flow, is observed. The structures form behind the obstacle, in a region with a strong velocity shear, but also other instability mechanisms can be identified. The dynamics of these structures is highly dependent on the physical parameters of the plasma, and they can either be quasi-stationary or undergo a dynamic evolution. The structures are found to be associated with phase-space vortices, observed especially in the phase space spanned by the velocity direction perpendicular to the flow and the spatial coordinate in the same direction. The bias of the obstacle with respect to the plasma potential is found to be an important parameter for the dynamics of the structures, but seemingly not for their formation as such. The results can be of interest in the interpretation of structures in space plasmas as observed by instrumented spacecrafts.

Particle‐in‐cell simulations of stochastic electron acceleration

1989 ◽  
Vol 1 (12) ◽  
pp. 2530-2532 ◽  
Author(s):  
K. Akimoto ◽  
H. Karimabadi
Keyword(s):  
Electron Acceleration ◽  
Particle In Cell

scholarly journals Fast magnetic energy dissipation in relativistic plasma induced by high order laser modes

2016 ◽  
Vol 4 ◽  
Author(s):  
Y. J. Gu ◽  
Q. Yu ◽  
O. Klimo ◽  
T. Zh. Esirkepov ◽  
S. V. Bulanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Energy ◽  
Collisionless Plasma ◽  
High Energy ◽  
Field Energy ◽  
Displacement Current ◽  
Particle In Cell ◽  
Magnetic Field Energy ◽  
High Energy Electrons

Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.

scholarly journals EVOLUTION OF THE WAKE WAVE EXCIDED BY THE SEQUENCE OF THE RELATIVISTIC ELECTRON BUNCHES

2019 ◽  
pp. 55-58
Author(s):  
O.K. Vynnyk ◽  
I.O. Anisimov
Keyword(s):  
Collisionless Plasma ◽  
Plasma Waves ◽  
Axially Symmetric ◽  
Particle In Cell ◽  
Wake Field ◽  
Electron Bunches ◽  
Density Maps ◽  
Wake Wave ◽  
Symmetric Geometry ◽  
Pic Code

The amplitude of plasma waves, excited by the resonant sequence of electron bunches, saturates after passage of some number of bunches. This behavior was observed and simulated, using particle-in-cell code, but was not completely explained yet. Our study of this behavior was carried out via computer simulation, using modified PDP3 code − 2D3V PIC code for axially symmetric geometry and relativistic collisionless plasma. Simulation demonstrated that amplitude saturation was caused by the plasma pressing-out from the area of the most intensive wake field. This hypothesis has been verified by the obtained electrical and magnetic field spectra, temperature and density maps and density profile for various simulation times.

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