On the Dynamic Accessibility of Toroidal Belt Pinch Equilibria.

摘要

Topological constraints on the motion of finite toroidal systems are employed to show that most force-free field configurations in a belt pinch geometry are not dynamically accessible via an adiabatic compression of force-free fields. This result is independent of any stability considerations. The leading asymptotic term (in the ratio column width/column height), for equilibria which are accessible via a radial motion, is determined by requiring that poloidal flux surfaces must also be poloidal current surfaces. As an application, it is shown that if the belt pinch column is a uniform, beta = 1, column, surrounded by a force-free field region, then near the interface the magnitude of the poloidal magnetic field is a decreasing function of the poloidal flux, and toroidal currents in the sheath and neighboring force-free field region are opposed. Moreover, near the toroidal midplane, both inner and outer portions of the interface have similarly directed radial velocities. (Author)