Collisionless residual zonal flow level of toroidally axisymmetric plasmas with arbitrary aspect ratio and elongation

The collisionless residual zonal flow level is calculated for toroidally axisymmetric plasmas with arbitrary aspect ratio and large elongation. For small aspect ratio, this level deviates largely from that predicted by the Rosenbluth–Hinton formula and retains a finite value. Plasma shaping such as elongation is favorable for retaining the residual zonal flow as well. The trapped particles make a major contribution to the neoclassical polarization.