Abstract Details
Abstracts
Author: Ilon Joseph
Requested Type: Consider for Invited
Submitted: 2024-03-29 15:14:10
Co-authors:
Contact Info:
Lawrence Livermore National Lab
PO Box 808
Livermore, 94551-0
USA
Abstract Text:
The polarization of charged particles in a strong magnetic field plays a central role in the adiabatic theory of magnetized plasmas. Both electric fields and thermodynamic forces, such as pressure and temperature gradients, generate plasma polarization and both are needed to determine the electric field self-consistently. Polarization arises due to the finite width of particle orbits due to the gyro-motion, the parallel circulation and bouncing motion, and the toroidal drift motion. We derive an efficient framework for calculating polarization at arbitrary collisionality to second order in gyroradius to scale length. Like gyrokinetic polarization, bounce-kinetic polarization displays a paradox: the diamagnetic polarization differs by a factor of 1/2 depending on whether one compares the real space density to the density in action-angle coordinates or to the density in the limit of zero orbit width.
In regions that are well-confined, the equilibrium particle distribution function can only depend on the robust constants of the motion. Because the total energy and toroidal momentum are conserved, they do not generate net polarization effects: the electric and thermodynamic polarizations must precisely cancel. In contrast, anisotropic dependance on the magnetic moment and parallel invariant generate a net polarization proportional to the temperature anisotropy. Dependence on toroidal momentum generates toroidal rotation and a charge separation due to drifts. Using radial force balance, this can be expressed as a drift-induced polarization density that scales as the poloidal gyroradius squared. Because it also depends on the poloidal flow, on collisional timescales, this introduces a polarization due to thermal forces in addition to the pressure gradient. The final result extends toroidal momentum conservation by consistently including the effects of gyrokinetic and parallel-bounce-kinetic polarization.
Comments:
Please group with other LLNL gyrokinetic/kinetic presentations.