Guiding Center Motion and Plasma Behavior in the Bumpy Torus

Abstract

Drift surfaces of guiding centers in the Bumpy Torus static magnetic field have been located and analyzed for various torus parameters by making use of the transverse adiabatic invariant μ = p_⊥²/B and the longitudinal adiabatic invariant J = ∮ p_∥ dl. In addition, the drift equations (for which μ is an invariant) have been solved numerically to investigate limitations on the application of the invariance of J. In general, J is an invariant for the drift equations under adiabatic conditions; however, some special guiding‐center trajectories are presented for which the drift per longitudinal period is sufficiently large that the assumption of the invariance of J is not valid. Closed surfaces of constant U = ∮ B⁻¹ dl have been found. These are also surfaces of constant plasma pressure under static equilibrium conditions at low β for a hydromagnetic model. The stability of the equilibrium is discussed.