title: Grad-Shafranov equilibria with negative core toroidal current in Tokamak plasmas.
abstract: Numerical Grad-Shafranov (GS) equilibria with negative current density in the plasma core are computed which do not impose any particularly chosen models for the pressure and current-density profiles. This flexibility allows the profiles to be tailored so that an island unfolds in the low-field side, even for elongated plasmas, thus sustaining the negative-current core against outward forces. Among other topological results, reversed GS equilibria are also shown to be necessarily non-nested, except for the cylindrical and other very special degenerate, hence structurally unstable cases.
authors.affiliation: Centro de Fusão Nuclear, Associação Euratom--IST, Instituto Superior Técnico, 1049-001 Lisboa, Portugal. par@cfn.ist.utl.pt
authors.forename: Paulo
authors.initials: P
authors.lastname: Rodrigues
authors.forename: João P S
authors.initials: JP
authors.lastname: Bizarro