Transport suppression by diamagnetic phase shift as a possible mechanism of the low to high mode transition

Publisher Website
Google Scholar
Abstract
In the presence of a pressure gradient, the phase velocity of drift wave or ion temperature gradient(ITG)modeturbulence is different from the average poloidal E×B rotation velocity of the guiding centers. This results in an Ẽ×Bturbulent particle diffusion being suppressed by the phase shift due to the diamagnetic rotation velocity u θ=(c/enB)dP/dr. This shift cannot be eliminated by a change of frame and affects the plasma transport. For u θ well above the turbulentẼ×B velocity, the radial diffusivity is suppressed as D∝u −3 θ. This results in a nonmonotonous particle flux Γ(∇ n)≂−D 0 ∇ n[1+α(∇ n)2]−3/2 such that the transport can develop a bifurcation at a realistic density gradient.