A Heuristic Coulomb Collision Operator for Cylindrical Velocity Coordinates

2000 ◽  
Vol 534 (2) ◽  
pp. 997-1007
Author(s):  
Geoffrey T. Lenters ◽  
James A. Miller ◽  
James C. Sommer
Keyword(s):  
Collision Operator ◽  
Coulomb Collision ◽  
Coulomb Collision Operator

scholarly journals Linear theory of electron-plasma waves at arbitrary collisionality

2019 ◽  
Vol 85 (2) ◽  
Author(s):  
R. Jorge ◽  
P. Ricci ◽  
S. Brunner ◽  
S. Gamba ◽  
V. Konovets ◽  
...  
Keyword(s):  
Electron Distribution Function ◽  
Collision Operator ◽  
Plasma Waves ◽  
Electron Plasma ◽  
Coulomb Collision ◽  
Particle Collisions ◽  
Angle Scattering ◽  
Damping Rate ◽  
Coulomb Collision Operator ◽  
Ion Collision

The dynamics of electron-plasma waves is described at arbitrary collisionality by considering the full Coulomb collision operator. The description is based on a Hermite–Laguerre decomposition of the velocity dependence of the electron distribution function. The damping rate, frequency and eigenmode spectrum of electron-plasma waves are found as functions of the collision frequency and wavelength. A comparison is made between the collisionless Landau damping limit, the Lenard–Bernstein and Dougherty collision operators and the electron–ion collision operator, finding large deviations in the damping rates and eigenmode spectra. A purely damped entropy mode, characteristic of a plasma where pitch-angle scattering effects are dominant with respect to collisionless effects, is shown to emerge numerically, and its dispersion relation is analytically derived. It is shown that such a mode is absent when simplified collision operators are used, and that like-particle collisions strongly influence the damping rate of the entropy mode.

Full Coulomb collision operator in the moment expansion

2009 ◽  
Vol 16 (10) ◽  
pp. 102108 ◽  
Author(s):  
Jeong-Young Ji ◽  
Eric D. Held
Keyword(s):  
Collision Operator ◽  
Coulomb Collision ◽  
Moment Expansion ◽  
The Moment ◽  
Coulomb Collision Operator

scholarly journals Nonlinear gyrokinetic Coulomb collision operator

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
R. Jorge ◽  
B. J. Frei ◽  
P. Ricci
Keyword(s):  
Spatial Scales ◽  
Collision Operator ◽  
Multipole Expansion ◽  
Distribution Functions ◽  
Larmor Radius ◽  
Coulomb Collision ◽  
Plasma Dynamics ◽  
Confinement Fusion ◽  
Far From Equilibrium ◽  
Coulomb Collision Operator

A gyrokinetic Coulomb collision operator is derived, which is particularly useful to describe the plasma dynamics at the periphery region of magnetic confinement fusion devices. The derived operator is able to describe collisions occurring in distribution functions arbitrarily far from equilibrium with variations on spatial scales at and below the particle Larmor radius. A multipole expansion of the Rosenbluth potentials is used in order to derive the dependence of the full Coulomb collision operator on the particle gyroangle. The full Coulomb collision operator is then expressed in gyrocentre phase-space coordinates, and a closed formula for its gyroaverage in terms of the moments of the gyrocentre distribution function in a form ready to be numerically implemented is provided. Furthermore, the collision operator is projected onto a Hermite–Laguerre velocity space polynomial basis and expansions in the small electron-to-ion mass ratio are provided.

scholarly journals A drift-kinetic analytical model for scrape-off layer plasma dynamics at arbitrary collisionality

2017 ◽  
Vol 83 (6) ◽  
Author(s):  
R. Jorge ◽  
P. Ricci ◽  
N. F. Loureiro
Keyword(s):  
Collision Operator ◽  
Distribution Functions ◽  
Lagrangian Description ◽  
Coulomb Collision ◽  
Fluid Models ◽  
Plasma Dynamics ◽  
Kinetic Boltzmann Equation ◽  
Far From Equilibrium ◽  
Layer Region ◽  
Coulomb Collision Operator

A drift-kinetic model to describe the plasma dynamics in the scrape-off layer region of tokamak devices at arbitrary collisionality is derived. Our formulation is based on a gyroaveraged Lagrangian description of the charged particle motion, and the corresponding drift-kinetic Boltzmann equation that includes a full Coulomb collision operator. Using a Hermite–Laguerre velocity space decomposition of the gyroaveraged distribution function, a set of equations to evolve the coefficients of the expansion is presented. By evaluating explicitly the moments of the Coulomb collision operator, distribution functions arbitrarily far from equilibrium can be studied at arbitrary collisionalities. A fluid closure in the high-collisionality limit is presented, and the corresponding fluid equations are compared with previously derived fluid models.

Transition in electron physics of magnetic reconnection in weakly collisional plasma

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
A. Le ◽  
J. Egedal ◽  
W. Daughton ◽  
V. Roytershteyn ◽  
H. Karimabadi ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Three Dimensional ◽  
Flux Rope ◽  
Collision Operator ◽  
Electron Velocity ◽  
Coulomb Collision ◽  
Kinetic Regime ◽  
Electron Velocity Distribution ◽  
Particle In Cell ◽  
Coulomb Collision Operator

Using particle-in-cell (PIC) simulations with a Monte Carlo treatment of the Coulomb collision operator, we study the transition in electron dynamics of magnetic reconnection for various levels of collisionality. The weakly collisional cases considered all fall into the so-called Hall or kinetic regime. Nevertheless, collisions may still alter the electron kinetic physics characteristic of collisionless reconnection, where adiabatic trapping energizes the electrons and leads to strong anisotropy of the electron velocity distribution and pressure. This anisotropy can support extended current sheets, associated with secondary island formation and turbulent flux rope interactions in three dimensional systems. The collisional simulations demonstrate how weak collisions may modify or eliminate these electron structures in the kinetic regimes. While the reconnection rate is not sensitive to the collisionality in the range studied, we find that increasing collisionality reduces the level of electron energization near the reconnection site. Finally, the results provide guidance for new laboratory reconnection experiments that will access the weakly collisional regimes.

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