ITR/(DMS): A Computational Environment for Multi-scale MHD Turbulence Studies

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Modeling MHD (magneto-hydrodynamic) turbulence has become increasinglyimportant both in terrestrial and engineering applications, such asfusion devices and plasma propulsion, as well as in space andastrophysical environments such as the solar wind and astrophysicaljets. The magneto-hydrodynamic nature of the plasma fluid imposesconstraints on the numerical procedures involved. Likewise, modeling inthe turbulent regime -- for turbulence is ubiquitous -- also imposesconstraints and challenges on the numerical procedures employed. Thenumerical approach and demands of computation time and accuracytranslate into algorithmic (or software) advances which can avail thehardware -- itself advancing rapidly. In this project these advancesentail: Adaptively refined grids, where fine resolution only in regionsof interest reduces overall CPU requirements; MHD shock capturingmethods, which improve accuracy of the calculation; parallel computingtechniques, which take advantage of the availability of multipleprocessors and memory and cache hierarchy; and sub-grid models, whichallow coarser grids than otherwise for turbulent regimes. The analysisof the resulting large multi-block multi-processor data requiresadvanced data visualization tools to examine the physics, the raisond'etre for the calculations. The project will develop a computationalenvironment, consisting of a 3D MHD simulation code with adaptive gridrefinement capabilities, complex time-dependent boundary conditions andoptimized to run under MPI on various parallel computers, and avisualization system that can handle multi-block multi-processor MHD AMRdata.In this end-to-end modeling and discovery process, informationtechnology (IT) plays a critical role. From software engineeringprinciples that result in robust codes, and smarter data structures thatare required for AMR, to single-node optimization and bettercommunication strategies on parallel architectures, to visualizationtool development and implementation, IT makes possible knowledgediscovery through simulation in a more efficient and orderly fashion.The requirements for MHD turbulence modeling being so considerable, thisefficiency of IT translates into enabling the science or technology.I.e. without the application of these IT principles, physicallyimportant and interesting regimes would not be analyzed. The results ofthis project will significantly enhance the modeling capabilities ofdiverse flows and will specifically be applied to the problem ofheliospheric magnetic field configuration and solar wind turbulence. 3DMHD simulations of the heliospheric fields and flows that includerotation, shear, waves, turbulence, current sheets, pressure-balancedstructures, and interaction regions, which thus represent most of themajor physical effects of importance, will be performed. The effort willenable future studies on particle propagation and magnetic fieldconfiguration for "space weather" effects on Earth. The project willdirectly train a post-doctoral scholar and a graduate student inrelevant physics and computational mathematics; project results will becommunicated to the community via conference and journal publicationsand the web, and through classes taught by the PI.