Role of edge electric field and poloidal rotation in the L-H transition.

Marked changes in the edge radial electric field {ital E}{sub {ital r}} and in the edge poloidal rotation velocity {ital v}{sub {theta}} are important signatures of the {ital L}-{ital H} transition in the DIII-D tokamak. Shear exists in {ital E}{sub {ital r}} and {ital v}{sub {theta}} and increases from the {ital L} mode to the {ital H} mode. A comparison of experiment with theory shows that shear in {ital E}{sub {ital r}} and {ital v}{sub {theta}} is sufficient to suppress edge fluctuations, that ion-orbit loss is large enough to be the source of {ital v}{sub {theta}}, and that {ital E}{sub {ital r}} and {ital v}{sub {theta}} may play a causal role in the {ital L}-{ital H} transition.