Interaction of bootstrap-current-driven magnetic islands

Technical Report · Tue Oct 01 00:00:00 EDT 1991

DOI:https://doi.org/10.2172/5071458· OSTI ID:5071458

Hegna, C C; Callen, J D

The formation and interaction of fluctuating neoclassical pressure gradient driven magnetic islands is examined. The interaction of magnetic islands produces a stochastic region around the separatrices of the islands. This interaction causes the island pressure profile to be broadened, reducing the island bootstrap current and drive for the magnetic island. A model is presented that describes the magnetic topology as a bath of interacting magnetic islands with low to medium poloidal mode number (m {congruent} 3{minus}30). The islands grow by the bootstrap current effect and damp due to the flattening of the pressure profile near the island separatrix caused by the interaction of the magnetic islands. The effect of this sporadic growth and decay of the islands ( magnetic bubbling'') is not normally addressed in theories of plasma transport due to magnetic fluctuations. The nature of the transport differs from statistical approaches to magnetic turbulence since the radial step size of the plasma transport is now given by the characteristic island width. This model suggests that tokamak experiments have relatively short-lived, coherent, long wavelength magnetic oscillations present in the steep pressure-gradient regions of the plasma. 42 refs.

• Research Organization: Wisconsin Univ., Madison, WI (United States). Center for Plasma Theory and Computation
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-86ER53218
• OSTI ID: 5071458
• Report Number(s): UW-CPTC-91-16; ON: DE92002625; TRN: 91-031430
• Country of Publication: United States
• Language: English

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