Abstract
The equilibrium state of a long tubular plasma with reversed trapped magnetic fields is discussed. It is shown that an equilibrium position stable to longitudinal perturbations exists for each value of the ratio of external to trapped flux providing the cross-sectional area of the plasma is less than half the total area of the system.
Variations in the containing magnetic field give rise to variations in the length and the cross-sectional area of the plasma tube. With observations confined to the end-view of the plasma and assuming that the tube did not vary in length, the observed variation in cross-sectional area would lead one to an assumption of an apparent value of γ = 4 for the plasma.