A toroidal flow antiparallel to the $〈E_r\times B_{\theta }〉$ drift direction is observed in the hot electron mode plasmas when a large positive electric field and a sharp electron temperature gradient are sustained inside the internal transport barrier in the Compact Helical System. This toroidal flow reaches up to $5\times {10}^4\mathrm{m}/\mathrm{s}$ at the plasma center, and it is large enough to reverse the toroidal flow driven by a tangentially injected neutral beam. These observations clearly show the plasma favors flow in the minimum ∇B direction at the transport barrier.

• Received 7 March 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.3040