Nonlinear theory of collisionless trapped ion modes

TY - JOUR

T1 - Nonlinear theory of collisionless trapped ion modes

AU - Hahm, T. S.

AU - Tang, W. M.

PY - 1996/1

Y1 - 1996/1

N2 - A simplified two-field nonlinear model for collisionless trapped-ion-mode turbulence has been derived from nonlinear bounce-averaged drift kinetic equations. The renormalized thermal diffusivity obtained from this analysis exhibits a Bohm-like scaling. A new nonlinearity associated with the neoclassical polarization density is found to introduce an isotope-dependent modification to this Bohm-like diffusivity. The asymptotic balance between the equilibrium variation and the finite banana width-induced reduction of the fluctuation potential leads to the result that the radial correlation length decreases with increasing plasma current. Other important conclusions from the present analysis include the predictions that (i) the relative density fluctuation level δn/n0 is lower than the conventional mixing length estimate, Δr/Ln; (ii) the ion temperature fluctuation level δTi/Ti significantly exceeds the density fluctuation level δn/n0; and (iii) the parallel ion velocity fluctuation level δνil/νTi is expected to be negligible.

AB - A simplified two-field nonlinear model for collisionless trapped-ion-mode turbulence has been derived from nonlinear bounce-averaged drift kinetic equations. The renormalized thermal diffusivity obtained from this analysis exhibits a Bohm-like scaling. A new nonlinearity associated with the neoclassical polarization density is found to introduce an isotope-dependent modification to this Bohm-like diffusivity. The asymptotic balance between the equilibrium variation and the finite banana width-induced reduction of the fluctuation potential leads to the result that the radial correlation length decreases with increasing plasma current. Other important conclusions from the present analysis include the predictions that (i) the relative density fluctuation level δn/n0 is lower than the conventional mixing length estimate, Δr/Ln; (ii) the ion temperature fluctuation level δTi/Ti significantly exceeds the density fluctuation level δn/n0; and (iii) the parallel ion velocity fluctuation level δνil/νTi is expected to be negligible.

UR - https://www.scopus.com/pages/publications/0009108780

UR - https://www.scopus.com/pages/publications/0009108780#tab=citedBy

U2 - 10.1063/1.871851

DO - 10.1063/1.871851

M3 - Article

SN - 1070-664X

VL - 3

SP - 242

EP - 247

JO - Physics of Plasmas

JF - Physics of Plasmas

IS - 1

ER -