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Computation of Resistive Inner Region Solutions with the DELTAC Code

Author: Alan H. Glasser
Requested Type: Poster Only
Submitted: 2015-01-15 13:45:05

Co-authors: Z.R.Wang, J.-K.Park

Contact Info:
University of Washington
3833 NE 155th St.
Lake Forest Park, WA   98155
USA

Abstract Text:
Recent work on the DCON stability code has extended its capability from ideal to resistive MHD. Using a singular Galerkin method with advanced basis functions, we compute outer region matching data in the neighborhood of the singular surfaces. Global analysis is completed with matched asymptotic expansions to resistive MHD solutions in the neighborhood of the singular surfaces. Comparison to the MARS-F code shows excellent agreement of growth rates and eigenfunctions for equilibria with one singular surface, dominated by odd-Ξ (tearing parity) solutions. With multiple singular surfaces, we find substantial discrepancies. The most likely cause is error in the computation of the even-Ξ (ballooning parity) inner region solution. We have compared the results of two inner region codes, one using 4th-order finite differences in configuration space, the other using an adaptive integrator in Fourier space. We find convergence for odd-Ξ solutions but not for even-Ξ solutions, and we have identified the cause of poor convergence. We have developed a new inner region code DELTAC, using a Galerkin expansion with advanced basis functions in configuration space. We will present a detailed description of this approach and comparison to the MARS-F code with multiple singular surfaces. We will also present a new derivation of the inner region equations, to be used as a basis for extending the physical content of the inner region equations.

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