Nonlinear coupling induced toroidal structure of edge localized modes. (21st December 2017)

• Record Type: Journal Article
• Authors: Mink, A.F.; Hoelzl, M.; Wolfrum, E.; Orain, F.; Dunne, M.; Lessig, A.; Pamela, S.; Manz, P.; Maraschek, M.; Huijsmans, G.T.A.; Becoulet, M.; Laggner, F.M.; Cavedon, M.; Lackner, K.; Günter, S.; Stroth, U.
• Other Names: collab.
• Is Part Of: Nuclear fusion. Volume 58:Number 2(2018:Feb.)
• Publication Date: 2017-12-21
• Subjects: plasma -- edge localized mode -- nonlinear -- mode number -- JOREK; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aa98f7
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Edge localized modes (ELMs) are magnetohydrodynamic (MHD) instabilities that cause fast periodic relaxations of the strong edge pressure gradient in tokamak fusion plasmas. A novel diagnostic method allows the extraction of toroidal mode numbers, rotation velocities and spatial information during the ELM cycle including the crash. While mode number branches n = 3 –6 and n = 8 –10 are dominant just before the ELM crash, during the ELM crash n = 2 –5 are observed in typical discharges with type-I ELMs in the tokamak experiment. These findings are compared to results from nonlinear MHD simulations. Although n = 6 is linearly dominant, nonlinear coupling in which n = 1 is particularly important leads to the dominance of n = 3 –5 during the ELM crash, in excellent agreement with experimental observations. The simultaneous occurrence of these modes over a wide radial region leads to high stochasticity and thus increased transport.