Z Pinch Kinetics I -- A Particle Perspective: Transitional Magnetization and Cyclotron and Betatron Orbits

Single-particle orbits are investigated as the basis of a coherent kinetic theory. Analytic solutions including azimuthal circulation are obtained in elliptic functions, of which ideal cyclotron and betatron motions are limiting solutions. The elliptic modulus depends on a trapping parameter and an axis-encircling to axial-drift kinetic energy ratio. Large trapping parameters limit to guiding-center cyclotron motion, while small trapping parameters describe ideal betatron motion. The analytic solutions inform a separation of phase space into trapped and passing trajectories, with which the Bennett solution is decomposed into cyclotron and betatron distributions. The two partial densities are computed to reveal a transitional magnetization layer the extent of which depends only on an ensemble-averaged trapping parameter, equivalent to: the Budker parameter, the pinch-to-Alfvén current ratio, the Larmor radius parameter squared, the Hall parameter squared, the drift parameter squared, and the Hartmann number squared. The interplay of diamagnetic current and axial betatron flux is clarified through partial current densities, and the radial electric fields of shear flows are observed to influence ion orbits particularly around unity Budker parameter.