Abstract Details
Abstracts
Author: Ilon Joseph
Requested Type: Poster
Submitted: 2025-03-14 08:57:51
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Contact Info:
Lawrence Livermore National Lab
7000 East Ave.
Livermore, CA 94551
USA
Abstract Text:
Many astrophysical plasmas and innovative confinement concepts have strong magnetic fields but do not necessarily satisfy the assumptions required for standard guiding center (GC) and gyrokinetic (GK) theory. Strong electric field gradients and shear flows can invalidate the basic assumptions because the Larmor orbits deform from circular to elliptical trajectories, the drifts become anisotropic in response to external forces, and additional curvature drifts must be included [1]. Hence, there is a pressing need to develop more accurate models that have a wider region of convergence. In fact, adiabatic theory is much more general than the standard GC/GK approach because it allows for more extreme types of orbital motion than simple circular motion. Moreover, adiabatic Kolmogorov-Arnold-Moser (KAM) theory converges at an exponentially fast rate that far surpasses traditional perturbation methods because, like Newton’s method, it renormalizes the zeroth order frequency at each outer stage.
In this work, the GC equations are extended to the strongest possible electric field gradients and shear flows while including spatial variations of the magnetic field. This is accomplished by developing a symplectic version of KAM theory that renormalizes the effective magnetic field at each outer stage. Performing the calculation in a moving reference frame simplifies the results. For small shear flows, the gyrofrequency is corrected by the parallel component of the vorticity in a manner that correctly reproduces the Banos drift. For large shear flows, the oscillation frequency also depends on the gradients in the electric field. The polarization and magnetization are modified by the change in gyrofrequency, by the large drift flows, and must include self-consistent thermodynamic polarization. Yet, the theory is similar in mathematical form to the standard case and can readily be implemented within existing simulation tools.
I. Joseph, Phys. Plasmas 28 (2021) 042102
Characterization: 4.0
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