Reynolds Stress-Driven Edge Momentum Transport in DIII-D

Tokamak plasma rotate toroidally due to an intrinsic edge source [1]. Reynolds Stress has been proposed $\langle$nv$_\phi$v$_\rho$$\rangle$=$\langle$n$\rangle$$\langle$\tilde{v}$_\phi$ \tilde{v}$_\rho$$\rangle$+$\hspace{0mm}$$\langle$v$_\phi$$\rangle$$\langle$\~n$_\phi$\tilde{v}$_\rho$$\rangle$+$\hspace{0mm}$$\langle$\tilde{n}$\tilde{v}$_\phi$\tilde{v}$_\rho$$\rangle$ as the transport mechanism. The term $\langle$n$\rangle$$\langle$\tilde{v}$_\phi$\tilde{v}$_\rho$$\rangle$ peaking $\sim$-1e26m$^\wedge$-1s$^\wedge$2 just inside the separatrix, causes a significant inward pinch due to cross-phase effects while the outward convection term, $\langle$v$_\phi$$\rangle$$\langle$$\tilde{n}$\tilde{v}$_\rho$$\rangle$, peaking at $\sim$-1E26m$^\wedge$-1s$^\wedge$2 roughly balances it. Surprisingly, the triple correlation term, $\langle$\tilde{n}$\tilde{v}$_\rho$\tilde{v}$_\phi$$\rangle$ peaking at t$\sim$-1E25m$^\wedge$-1s$^\wedge$2 becomes important as other terms almost null out. A rough momentum balance finds that the momentum flux from the RS term can explain the observed momentum balance.