title: Zonal flow and zonal magnetic field generation by finite beta drift waves: a theory for low to high transitions in tokamaks.
abstract: The understanding of low to high (L-H) transition in tokamaks has been an important area of investigation for more than a decade. Recent 3D finite beta simulations of drift-resistive ballooning modes in a flux tube geometry by Rogers et al. [Phys. Rev. Lett. 81, 4396 (1998)] have provided a unique parametrization of the transition in a two-dimensional phase space. Comparison of the threshold curve in this phase space with data from ASDEX and C-MOD has shown very good agreement. In this Letter we provide a simple theory, based on the generation of zonal flow and zonal magnetic field in a finite-beta plasma, which explains this threshold curve for L-H transition in tokamaks.
authors.affiliation: Institute for Plasma Research, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: P N
authors.initials: PN
authors.lastname: Guzdar
authors.forename: R G
authors.initials: RG
authors.lastname: Kleva
authors.forename: A
authors.initials: A
authors.lastname: Das
authors.forename: P K
authors.initials: PK
authors.lastname: Kaw