scholarly journals Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
Jonathan O. Thurgood ◽  
David Tsiklauri
Keyword(s):  
Solar Wind ◽  
Electron Beam ◽  
Linear Theory ◽  
Langmuir Wave ◽  
High Energy ◽  
Density Fluctuations ◽  
Langmuir Waves ◽  
Particle In Cell ◽  
Hamiltonian Models ◽  
Beam Plasma

Previous theoretical considerations of electron beam relaxation in inhomogeneous plasmas have indicated that the effects of the irregular solar wind may account for the poor agreement of homogeneous modelling with the observations. Quasi-linear theory and Hamiltonian models based on Zakharov’s equations have indicated that when the level of density fluctuations is above a given threshold, density irregularities act to de-resonate the beam–plasma interaction, restricting Langmuir wave growth on the expense of beam energy. This work presents the first fully kinetic particle-in-cell (PIC) simulations of beam relaxation under the influence of density irregularities. We aim to independently determine the influence of background inhomogeneity on the beam–plasma system, and to test theoretical predictions and alternative models using a fully kinetic treatment. We carry out one-dimensional (1-D) PIC simulations of a bump-on-tail unstable electron beam in the presence of increasing levels of background inhomogeneity using the fully electromagnetic, relativistic EPOCH PIC code. We find that in the case of homogeneous background plasma density, Langmuir wave packets are generated at the resonant condition and then quasi-linear relaxation leads to a dynamic increase of wavenumbers generated. No electron acceleration is seen – unlike in the inhomogeneous experiments, all of which produce high-energy electrons. For the inhomogeneous experiments we also observe the generation of backwards-propagating Langmuir waves, which is shown directly to be due to the refraction of the packets off the density gradients. In the case of higher-amplitude density fluctuations, similar features to the weaker cases are found, but also packets can also deviate from the expected dispersion curve in $(k,\unicode[STIX]{x1D714})$-space due to nonlinearity. Our fully kinetic PIC simulations broadly confirm the findings of quasi-linear theory and the Hamiltonian model based on Zakharov’s equations. Strong density fluctuations modify properties of excited Langmuir waves altering their dispersion properties.

scholarly journals Ion dynamics in electron beam–plasma interaction: particle-in-cell simulations

2014 ◽  
Vol 32 (8) ◽  
pp. 1025-1033 ◽  
Author(s):  
K. Baumgärtel
Keyword(s):  
Electron Beam ◽  
Langmuir Wave ◽  
Density Fluctuations ◽  
Wave Number ◽  
Random Wave ◽  
Ion Density ◽  
Plasma Interaction ◽  
Particle In Cell ◽  
Beam Plasma ◽  
Electron Beam Plasma

Abstract. Electron beam–plasma interaction including ions is studied by particle-in-cell (PIC) simulations using a one-dimensional, electrostatic code. Evidence for Langmuir wave decay is given for sufficiently energetic beams, as in previous Vlasov–Maxwell simulations. The mechanism for the generation of localized finite-amplitude ion density fluctuations is analyzed. Amplitude modulation due to interference between the beam-generated Langmuir waves causes random wave localization including strong transient spikes in field intensity which create bursty ion density structures via ponderomotive forces. More dense beams may quench the decay instability and generate low-frequency variations dominated by the wave number of the fastest growing Langmuir mode.

scholarly journals Electron beam relaxation in inhomogeneous plasmas

2013 ◽  
Vol 31 (8) ◽  
pp. 1379-1385 ◽  
Author(s):  
A. Voshchepynets ◽  
V. Krasnoselskikh
Keyword(s):  
Electron Beam ◽  
Beam Energy ◽  
Electron Beams ◽  
Inhomogeneous Plasma ◽  
Density Fluctuations ◽  
Langmuir Waves ◽  
Wave Trapping ◽  
Beam Plasma ◽  
Beam Plasma Instability ◽  
Accelerated Particles

Abstract. In this work, we studied the effects of background plasma density fluctuations on the relaxation of electron beams. For the study, we assumed that the level of fluctuations was so high that the majority of Langmuir waves generated as a result of beam-plasma instability were trapped inside density depletions. The system can be considered as a good model for describing beam-plasma interactions in the solar wind. Here we show that due to the effect of wave trapping, beam relaxation slows significantly. As a result, the length of relaxation for the electron beam in such an inhomogeneous plasma is much longer than in a homogeneous plasma. Additionally, for sufficiently narrow beams, the process of relaxation is accompanied by transformation of significant part of the beam kinetic energy to energy of accelerated particles. They form the tail of the distribution and can carry up to 50% of the initial beam energy flux.

scholarly journals Fundamental Electromagnetic Emissions by a Weak Electron Beam in Solar Wind Plasmas with Density Fluctuations

2022 ◽  
Vol 924 (2) ◽  
pp. L24
Author(s):  
C. Krafft ◽  
P. Savoini
Keyword(s):  
Electron Beam ◽  
Electromagnetic Radiation ◽  
Inhomogeneous Plasma ◽  
Langmuir Wave ◽  
Density Fluctuations ◽  
Electromagnetic Energy ◽  
Langmuir Waves ◽  
Harmonic Emission ◽  
Electromagnetic Emissions ◽  
Weak Electron

Abstract The generation of Langmuir wave turbulence by a weak electron beam in a randomly inhomogeneous plasma and its subsequent electromagnetic radiation are studied owing to two-dimensional particle-in-cell simulations in conditions relevant to type III solar radio bursts. The essential impact of random density fluctuations of average levels of a few percents of the background plasma on the characteristics of the electromagnetic radiation at the fundamental plasma frequency ω p is shown. Not only wave nonlinear interactions but also processes of Langmuir waves’ transformations on the density fluctuations contribute to the generation of such emissions. During the beam relaxation, the amount of electromagnetic energy radiated at ω p in a plasma with density fluctuations strongly exceeds that observed when the plasma is homogeneous. The fraction of Langmuir wave energy involved in the generation of electromagnetic emissions at ω p saturates around 10−4, i.e., one order of magnitude above that reached when the plasma is uniform. Moreover, whereas harmonic emission at 2ω p dominates over fundamental emission during the time evolution in a homogeneous plasma, fundamental emission is strongly dominant when the plasma contains density fluctuations, at least during several thousands of plasma periods before being overcome by harmonic emission when the total electromagnetic energy begins to saturate.

scholarly journals 1-D particle-in-cell simulations of electron acoustic solitary structures in an electron beam-plasma

AIP Advances ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 025029 ◽  
Author(s):  
A. A. Abid ◽  
Quanming Lu ◽  
M. N. S. Qureshi ◽  
X. L. Gao ◽  
Huayue Chen ◽  
...  
Keyword(s):  
Electron Beam ◽  
Particle In Cell ◽  
Beam Plasma ◽  
Solitary Structures ◽  
Electron Acoustic ◽  
Electron Beam Plasma

EARLY OUT-OF-EQUILIBRIUM BEAM-PLASMA EVOLUTION: POSSIBLE FORMATION OF A BEAM RING STRUCTURE

2007 ◽  
Vol 21 (03n04) ◽  
pp. 633-636 ◽  
Author(s):  
M. C. FIRPO ◽  
A. F. LIFSCHITZ
Keyword(s):  
Electron Beam ◽  
Transverse Isotropy ◽  
Ring Structure ◽  
Skin Depth ◽  
Beam Radius ◽  
Particle In Cell ◽  
Beam Plasma ◽  
Initial Stage ◽  
Filamentation Instability ◽  
Beam Edge

We solve analytically the out-of-equilibrium initial stage that follows the injection of a radially finite electron beam into a plasma at rest and test it against particle-in-cell simulations. For initial large beam edge gradients and not too large beam radius, compared to the electron skin depth, the electron beam is shown to evolve into a ring structure. For low enough transverse temperatures, filamentation instability eventually proceeds and saturates when transverse isotropy is reached. The analysis accounts for the variety of very recent experimental beam transverse observations.

scholarly journals Coherent amplitude modulation of electron-beam-driven Langmuir waves

2013 ◽  
Vol 31 (4) ◽  
pp. 633-638 ◽  
Author(s):  
K. Baumgärtel
Keyword(s):  
Electron Beam ◽  
Amplitude Modulation ◽  
Linear Analysis ◽  
Uniform Domain ◽  
Periodic Modulation ◽  
Langmuir Waves ◽  
Plasma Oscillations ◽  
Plasma Interaction ◽  
Particle In Cell ◽  
Linear Approach

Abstract. A linear approach to the phenomenon of irregular amplitude modulation of beam-driven Langmuir waves, developed in a previous paper, is extended to explain periodic modulation as well. It comes about by beating of the fastest growing mode of the instability with beam-aligned plasma oscillations. They are naturally generated in a uniform domain of beam–plasma interaction prior to the onset of the instability. Particle-in-cell (PIC) simulations support the results of the linear analysis.

scholarly journals Direct observation of imploded core heating via fast electrons with super-penetration scheme

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
T. Gong ◽  
H. Habara ◽  
K. Sumioka ◽  
M. Yoshimoto ◽  
Y. Hayashi ◽  
...  
Keyword(s):  
Electron Beam ◽  
Direct Observation ◽  
Inertial Confinement Fusion ◽  
Short Pulse ◽  
Coupling Efficiency ◽  
High Energy ◽  
Inertial Confinement ◽  
Particle In Cell ◽  
Short Pulse Laser ◽  
Confinement Fusion

AbstractFast ignition (FI) is a promising approach for high-energy-gain inertial confinement fusion in the laboratory. To achieve ignition, the energy of a short-pulse laser is required to be delivered efficiently to the pre-compressed fuel core via a high-energy electron beam. Therefore, understanding the transport and energy deposition of this electron beam inside the pre-compressed core is the key for FI. Here we report on the direct observation of the electron beam transport and deposition in a compressed core through the stimulated Cu Kα emission in the super-penetration scheme. Simulations reproducing the experimental measurements indicate that, at the time of peak compression, about 1% of the short-pulse energy is coupled to a relatively low-density core with a radius of 70 μm. Analysis with the support of 2D particle-in-cell simulations uncovers the key factors improving this coupling efficiency. Our findings are of critical importance for optimizing FI experiments in a super-penetration scheme.

Electron beam-plasma discharge in GDT mirror trap: Particle-in-cell simulations

2021 ◽  
Author(s):  
Igor Timofeev ◽  
Vladimir Annenkov ◽  
Evgeniia Volchok ◽  
Vladimir Glinskiy
Keyword(s):  
Electron Beam ◽  
Electric Fields ◽  
Plasma Discharge ◽  
Magnetized Plasma ◽  
Beam Particle ◽  
Nonuniform Plasma ◽  
Particle In Cell ◽  
Beam Plasma ◽  
Transverse Electric Fields ◽  
Recent Laboratory

Abstract The paper presents the results of numerical simulations of the collective relaxation of an electron beam in a magnetized plasma at the parameters typical to experiments on the ignition of a beam-plasma discharge in the Gas Dynamic Trap. The goal of these simulations is to confirm the ideas about the mechanism of the discharge development, which are used to interpret the results of recent laboratory experiments [Soldatkina et al 2021 {\it Nucl. Fusion}]. In particular, a characteristic feature of these experiments is the localization of the beam relaxation region in the vicinity of the entrance mirror. A strong mirror magnetic field compresses the beam so that its transverse size becomes less than the wavelength it excites. In addition, near the mirror, the electron cyclotron frequency is much higher than the plasma one, which can significantly affect the possibility of propagation of the most unstable waves outside the beam. Particle-in-cell simulations make it possible not only to find how efficiently intense plasma oscillations penetrate the rarefied periphery, but also to prove that the turbulent zone in a realistic nonuniform plasma has regions dominated by transverse electric fields. This creates the necessary conditions for efficient acceleration of the trapped particles to energies much higher than the initial beam energy.

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