scholarly journals Slab magnetised non-relativistic low-beta electron–positron plasmas: collisionless heating, linear waves and reconnecting instabilities

2017 ◽  
Vol 83 (6) ◽  
Author(s):  
Alessandro Zocco
Keyword(s):  
Scale Effects ◽  
Kinetic Equations ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Displacement Current ◽  
Electron Mass ◽  
Slab Geometry ◽  
Tearing Modes ◽  
First Order ◽  
Electron Positron

The properties of a non-relativistic magnetised low-beta electron–positron plasma in slab geometry are investigated. The two species are taken to be drift kinetic while we retain Larmor radius effects in quasi-neutrality, and inertia in Ohm’s law. A linear analysis shows that, for small magnetic perturbations, Alfvénic perturbations travel at the electron Alfvén speed, which is based on the electron mass. We discuss the role of the displacement current when Larmor-scale and Debye-scale effects are both retained. We predict the existence of a kinetic electron Alfvén wave which connects to the K-modes of Mishchenko et al. (J. Plasma Phys., 2017 (submitted)) in the electrostatic limit. It is found that linear drift waves are not supported by the system if the two species have the same temperature. Tearing modes can be driven unstable by equilibrium current density gradients. Also in this case, the characteristic time is based on the electron Alfvén speed. Nonlinear hybrid fluid-kinetic equations are also derived. It is shown that each species is described, to leading order, by the kinetic reduced electron heating model (KREHM) kinetic equation of Zocco & Schekochihin (Phys. Plasmas, vol. 18, 2011, 102309). The model is extended to retain first-order Larmor radius effects. It supports collisionless dispersive waves, which can greatly impact nonlinear magnetic reconnection. Diamagnetic effects enter the nonlinear equations via the first-order magnetic compressibility. A minimal nonlinear model for two-dimensional low-frequency isothermal pair plasmas is derived.

Stability of relativistic anisotropic plasmas to perpendicular magnetosonic waves

1970 ◽  
Vol 4 (3) ◽  
pp. 495-510 ◽  
Author(s):  
R. W. Landau ◽  
S. Cuperman
Keyword(s):  
Dispersion Relation ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Interplanetary Medium ◽  
Alfven Wave ◽  
Larmor Radius ◽  
First Order ◽  
Ion Plasma ◽  
The Stability ◽  
The Magnetic Field

The stability of relativistic anisotropic plasmas to the magnetosonic (or righthand compressional Alfvén) wave, near the ion cyclotron frequency, propagating perpendicular to the magnetic field, is investigated. For this case, and for wavelengths larger than the ion Larmor radius and large ion plasma frequency () the dispersion relation is obtained in a simple form and solved. It is shown that for T‖ ╪ T⊥ (even T‖ ≥ T⊥) no instability occurs. This conclusion applies also to the case of the anisotropic interplanetary medium.We note a peculiarity of the dispersion relation. Zero-order and first-order terms cancel so that the relation is of second order in our expansion parameter. The non-relativistic numerical results of Fredricks and Kennel are recovered.

scholarly journals Gyrokinetic stability of electron–positron–ion plasmas

2018 ◽  
Vol 84 (1) ◽  
Author(s):  
A. Mishchenko ◽  
A. Zocco ◽  
P. Helander ◽  
A. Könies
Keyword(s):  
Dispersion Relation ◽  
Temperature Gradient ◽  
Electron Temperature ◽  
Alfven Wave ◽  
Ion Temperature ◽  
Slab Geometry ◽  
Ion Temperature Gradient ◽  
Electron Temperature Gradient ◽  
Electron Positron ◽  
Ion Proton

The gyrokinetic stability of electron–positron plasmas contaminated by an ion (proton) admixture is studied in a slab geometry. The appropriate dispersion relation is derived and solved. Stable K-modes, the universal instability, the ion-temperature-gradient-driven instability, the electron-temperature-gradient-driven instability and the shear Alfvén wave are considered. It is found that the contaminated plasma remains stable if the contamination degree is below some threshold and that the shear Alfvén wave can be present in a contaminated plasma in cases where it is absent without ion contamination.

scholarly journals Imbalanced kinetic Alfvén wave turbulence: from weak turbulence theory to nonlinear diffusion models for the strong regime

2019 ◽  
Vol 85 (03) ◽  
Author(s):  
T. Passot ◽  
P. L. Sulem
Keyword(s):  
Magnetic Field ◽  
Total Energy ◽  
Nonlinear Diffusion ◽  
Kinetic Equations ◽  
Turbulence Theory ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Weak Turbulence ◽  
Finite Larmor Radius ◽  
Electron Inertia

A two-field Hamiltonian gyrofluid model for kinetic Alfvén waves retaining ion finite Larmor radius corrections, parallel magnetic field fluctuations and electron inertia, is used to study turbulent cascades from the magnetohydrodynamic (MHD) to the sub-ion scales. Special attention is paid to the case of imbalance between waves propagating along or opposite to the ambient magnetic field. For weak turbulence in the absence of electron inertia, kinetic equations for the spectral density of the conserved quantities (total energy and generalized cross-helicity) are obtained. They provide a global description, matching between the regimes of reduced MHD at large scales and electron reduced MHD at small scales, previously considered in the literature. In the limit of ultra-local interactions, Leith-type nonlinear diffusion equations in the Fourier space are derived and heuristically extended to the strong turbulence regime by modifying the transfer time appropriately. Relations with existing phenomenological models for imbalanced MHD and balanced sub-ion turbulence are discussed. It turns out that in the presence of dispersive effects, the dynamics is sensitive on the way turbulence is maintained in a steady state. Furthermore, the total energy spectrum at sub-ion scales becomes steeper as the generalized cross-helicity flux is increased.

The Kinetics of Glucose Decomposition with Sulfate Reduction in the Anaerobic Fluidized Bed Reactor

1993 ◽  
Vol 28 (2) ◽  
pp. 135-144 ◽  
Author(s):  
S. Matsui ◽  
R. Ikemoto Yamamoto ◽  
Y. Tsuchiya ◽  
B. Inanc
Keyword(s):  
Sulfate Reduction ◽  
Fluidized Bed ◽  
Kinetic Equations ◽  
Fluidized Bed Reactor ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Glucose Decomposition ◽  
Reaction Equations ◽  
Kinetics Of

Using a fluidized bed reactor, experiments on glucose decomposition with and without sulfate reduction were conducted. Glucose in the reactor was mainly decomposed into lactate and ethanol. Lactate was mainly decomposed into propionate and acetate, while ethanol was decomposed into propionate, acetate, and hydrogen. Sulfate reduction was not involved in the decomposition of glucose, lactate, and ethanol, but was related to propionate and acetate decomposition. The stepwise reactions were modeled using either a Monod expression or first order reaction kinetics in respect to the reactions. The coefficients of the kinetic equations were determined experimentally. The modified Monod and first order reaction equations were effective at predicting concentrations of glucose, lactate, ethanol, propionate, acetate, and sulfate along the beight of the reactor. With sulfate reduction, propionate was decomposed into acetate, while without sulfate reduction, accumulation of propionate was observed in the reactor. Sulfate reduction accelerated propionate conversion into acetate by decreasing the hydrogen concentration.

scholarly journals Equilibration of the chiral asymmetry due to finite electron mass in electron-positron plasma

2021 ◽  
Vol 103 (1) ◽  
Author(s):  
A. Boyarsky ◽  
V. Cheianov ◽  
O. Ruchayskiy ◽  
O. Sobol
Keyword(s):  
Electron Mass ◽  
Chiral Asymmetry ◽  
Electron Positron

scholarly journals Kinetic Modelling of Biodegradability Data of Commercial Polymers Obtained under Aerobic Composting Conditions

Eng ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 54-68
Author(s):  
Ilenia Rossetti ◽  
Francesco Conte ◽  
Gianguido Ramis
Keyword(s):  
Kinetic Data ◽  
Kinetic Modelling ◽  
Kinetic Equations ◽  
Second Order ◽  
Aerobic Biodegradation ◽  
First Order ◽  
First Order Kinetics ◽  
Plastic Materials ◽  
Partial Degradation ◽  
Commercial Polymers

Methods to treat kinetic data for the biodegradation of different plastic materials are comparatively discussed. Different samples of commercial formulates were tested for aerobic biodegradation in compost, following the standard ISO14855. Starting from the raw data, the conversion vs. time entries were elaborated using relatively simple kinetic models, such as integrated kinetic equations of zero, first and second order, through the Wilkinson model, or using a Michaelis Menten approach, which was previously reported in the literature. The results were validated against the experimental data and allowed for computation of the time for half degradation of the substrate and, by extrapolation, estimation of the final biodegradation time for all the materials tested. In particular, the Michaelis Menten approach fails in describing all the reported kinetics as well the zeroth- and second-order kinetics. The biodegradation pattern of one sample was described in detail through a simple first-order kinetics. By contrast, other substrates followed a more complex pathway, with rapid partial degradation, subsequently slowing. Therefore, a more conservative kinetic interpolation was needed. The different possible patterns are discussed, with a guide to the application of the most suitable kinetic model.

scholarly journals Effects of Positron Density and Temperature on Large Amplitude Ion-acoustic Waves in an Electron - Positron - Ion Plasma

1997 ◽  
Vol 50 (2) ◽  
pp. 309 ◽  
Author(s):  
Y. N. Nejoh
Keyword(s):  
Acoustic Waves ◽  
Large Amplitude ◽  
Density Ratio ◽  
Present Theory ◽  
Electron Mass ◽  
Mass Ratio ◽  
Ion Acoustic Waves ◽  
Ion Plasma ◽  
Electron Positron ◽  
Ion Acoustic

The nonlinear wave structures of large amplitude ion-acoustic waves are studied in a plasma with positrons. We have presented the region of existence of the ion-acoustic waves by analysing the structure of the pseudopotential. The region of existence sensitively depends on the positron to electron density ratio, the ion to electron mass ratio and the positron to electron temperature ratio. It is shown that the maximum Mach number increases as the positron temperature increases and the region of existence of the ion-acoustic waves spreads as the positron temperature increases. The present theory is applicable to analyse large amplitude ion-acoustic waves associated with positrons which may occur in space plasmas.

scholarly journals Alfvenic perturbations with finite Larmor radius effect in non-Maxwellian electron–positron–ion plasmas

AIP Advances ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 025002 ◽  
Author(s):  
Saba Khalid ◽  
M. N. S. Qureshi ◽  
W. Masood
Keyword(s):  
Larmor Radius ◽  
Finite Larmor Radius ◽  
Electron Positron

scholarly journals QED RADIATIVE CORRECTIONS TO THE DECAY π0→e+e−

1993 ◽  
Vol 08 (18) ◽  
pp. 1691-1700 ◽  
Author(s):  
GEORGE TRIANTAPHYLLOU
Keyword(s):  
Perturbation Theory ◽  
Decay Rate ◽  
Invariant Mass ◽  
New Physics ◽  
Radiative Corrections ◽  
First Order ◽  
Recent Interest ◽  
Electron Positron ◽  
Electron Positron Pair ◽  
First Order Perturbation

In view of the recent interest in the decays of mesons into a pair of light leptons, a computation of the QED radiative corrections to the decay of π0 into an electron-positron pair is presented here. The analysis is based on the soft-photon resummation method, which, unlike first-order perturbation theory, allows for very strict invariant-mass cuts on the final electrons. When combined with the theoretical estimates for the non-radiatively corrected decay rate, the results of the present paper could help to determine if new physics affect this decay.

Small disturbances in a conducting fluid in the presence of a current-carrying conductor

1964 ◽  
Vol 60 (2) ◽  
pp. 325-339
Author(s):  
A. M. J. Davis
Keyword(s):  
Uniform Magnetic Field ◽  
Equations Of Motion ◽  
Conducting Fluid ◽  
Alfven Wave ◽  
Displacement Current ◽  
Wave Fronts ◽  
Acoustic Disturbance ◽  
Linear Partial Differential Equations ◽  
A Current ◽  
Small Disturbances

1. Introduction. The problem considered here derives its motivation from a paper by Friedlander (8) on the propagation of small disturbances in a compressible, conducting fluid in the presence of a uniform magnetic field (see also Courant and Hilbert (3), VI, §3a). In this the displacement current and energy dissipation by viscosity, heat conduction and Joule heat are neglected and a system of linear partial differential equations is obtained, which generalizes the equations of motion of the theory of sound. Their solution is in general the superposition of an arbitrary incompressible Alfven wave and a magneto-acoustic disturbance. This latter was considered by constructing a Green's function by means of suitable combinations of plane wave solutions and it was found that there are fast and slow wave fronts diverging from a point disturbance. The latter are conoidal in shape and have a singularity at their vertices which propagate along the field line in either direction from the source.

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