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GEM 2002 Student Tutorial Global MHD Simulation in Geospace Yongli Wang IGPP/UCLA Special Thanks to Dr. J. Raeder for hi

GEM 2002 Student Tutorial Global MHD Simulation in Geospace Yongli Wang IGPP/UCLA Special Thanks to Dr. J. Raeder for his help to prepare the material. Outline. Introduction to the Global MHD Simulation How to perform global MHD Simulation New Techniques and Challenges.

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GEM 2002 Student Tutorial Global MHD Simulation in Geospace Yongli Wang IGPP/UCLA Special Thanks to Dr. J. Raeder for hi

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  1. GEM 2002 Student TutorialGlobal MHD Simulation in GeospaceYongli WangIGPP/UCLASpecial Thanks to Dr. J. Raederfor his help to prepare the material 2002 GEM Student Tutorial

  2. Outline • Introduction to the Global MHD Simulation • How to perform global MHD Simulation • New Techniques and Challenges 2002 GEM Student Tutorial

  3. What Make Up the Space Physics? Observations Theories Synthesis Simulations 2002 GEM Student Tutorial

  4. Properties of Numerical Solution Methods • Why we use simulations: • Put spacecraft into context. • Parameter dependence study; • Boundary conditions; • Temporal dependence study; • Nonlinear problems; • Unobserved regions • Complex geometry • A robust simulation has the following properties: [J.H. Ferziger and M. Peric, Computational Methods for Fluid Dynamics, Springer, 1999] 2002 GEM Student Tutorial

  5. What is the Global MHD Simulation Global MHD simulation is the numerical simulation of the geospace environment with MHD equations as the governing equations. 2002 GEM Student Tutorial

  6. History of Global MHD Simulation • 1978: First 2d simulations by Leboeuf et al. • Early 1980’s: First 3d simulations (Brecht, Lyon, Wu, Ogino). • Late 1980’s: Model refinements (FACs, ionosphere, higher resolution, fewer symmetries). • Early 1990’s: Long geomagnetic tails, refined ionosphere models. • Mid 1990’s: First comparisons with in situ observations. Beginning of quantitative modeling. • Late 1990’s: Global models become an integrated part of many experimental studies and models provide extension to observations and theoretical studies. • Early 2000’s: Global models begin to be accessible for the whole community. Improved boundary conditions. 2002 GEM Student Tutorial

  7. MHD Theory and Equations • The basis of MHD: • Vlasov-Boltzman Equation • Maxwellian Equations • Some fundamental requirements for MHD • Debye Length and ND • Scale length is larger than ion gyro-radius and time scale should be larger than gyro-period. • Localization 2002 GEM Student Tutorial

  8. Grids 2002 GEM Student Tutorial

  9. Initial Condition • Criteria for initial condition: • Final configuration has no dependence on the initial condition • Small time to reach realistic configuration • Example 2002 GEM Student Tutorial

  10. Boundary Condition • Outer boundary: • Observational solar wind input • Idealized solar wind input • Input from solar wind models • Inner boundary: • Ionosphere; inner magnetosphere (Ring current) • Mapping; continuous 2002 GEM Student Tutorial

  11. Algorithms • Integration: • Spatial integration • Finite difference method • Finite volume method • Finite element method • Temporal integration • Multiple step method (predictor-corrector method) • Runge-Kutta method • Time step determination: CFL condition [J.H. Ferziger and M. Peric, Computational Methods for Fluid Dynamics, Springer, 1999 ] 2002 GEM Student Tutorial

  12. Parallelization • MPI (Message Passing Interface) • Designed for high performance on both massively parallel machines and on workstation clusters • Widely available: free or vendor supported. • Cross platform • Multiple language: Fortran, C/C++,… • Parallel computation facilities: • Massively parallel machines: CRAY-T3E, IBM-SP2, SGI-ORGIGIN2000, … • Workstation clusters : PC Beowulf clusters, … 2002 GEM Student Tutorial

  13. A Super Computer Example: IBM Bluehorizon 2002 GEM Student Tutorial

  14. Beowulf in My Office 2002 GEM Student Tutorial

  15. Fundamental Difficulties in MHD Simulation • How to Determine Resistivity • Progress in the field of computer fluid dynamics. however, there are extra difficulties for MHD • Much More complex MHD than Fluid • Divergence of B free • Special characteristics that MHD equations show compared to the simpler fluid equations. 2002 GEM Student Tutorial

  16. Current Major Global MHD Models • Dartmouth/NRL/Maryland LFM (J. Lyon, J.A. Fedder, C. Mobarry) • GEDAS (Japan, T. Ogino) • ISM (G.L. Siscoe) • Michigan BATS-R-US (T.I. Gombosi) • UCLA (J. Raeder) • U. of Washington (R.M. Winglee) • … … 2002 GEM Student Tutorial

  17. Outline • Introduction to the Global MHD Simulation • How to perform global MHD Simulation • New Techniques and Challenges 2002 GEM Student Tutorial

  18. Can a Non-Modeler Do Global Simulation? • Models are readily available for community use: • CCMC: http://ccmc.gsfc.nasa.gov/ • UCLA: http://www-ggcm2.igpp.ucla.edu/ • Source codes in public domain: • GEDAS (Japan, T. Ogino) http://gedas22.stelab.nagoya-u.ac.jp/simulation/jst2k/hpf02.html • BATSRUS: http://csem.engin.umich.edu/ • NRL: http://www.lcp.nrl.navy.mil/hpcc-ess/software.html • FCTMHD3D (C.R. DeVore) • AMRMHD3D (P. MacNeice) • Zeus 3D MHD (Michael Norman): http://zeus.ncsa.uiuc.edu:8080/lca_intro_zeus3d.html • CDF Codes: http://icemcfd.com/cfd/CFD_codes.html 2002 GEM Student Tutorial

  19. How to Make Global MHD Simulation What do you want to solve? Why do you want to use global model? What results do you expect from a global model? Set model parameters and provide necessary input files Run global model Analyze model results Possible combination with other results (theory, observation) Ready for publication? 2002 GEM Student Tutorial

  20. What Can We Do with Global MHD Model? • Space Weather • Magnetosphere dynamics (storm, substorm, magnetotail configuration) • Bow shock and magnetosheath dynamics • Solar wind-magnetosphere interaction • M-I coupling. • More reference can be found: http://pallas.igpp.ucla.edu/jraeder/http://ccmc.gsfc.nasa.gov/ 2002 GEM Student Tutorial

  21. How to Make Global MHD Simulation What do you want to solve? Why do you want to use global model? What results do you expect from a global model? Set model parameters and provide necessary input files Run global model Analyze model results Possible combination with other results (theory, observation) Ready for publication? 2002 GEM Student Tutorial

  22. Model parameters and solar wind input • Parameters in the model: • Computation domain settings (Simulation box size, grid settings) • Boundary condition (e.g., inner boundary location, boundary type) • Ionosphere conductivity (constant conductivity, empirical conductivity model, ionosphere model) • Resistivity parameters • Simulation run time • Data output control parameters (output frequency, output data location and type) • Debugging parameters (debugging message output) Click to see a sample parameter input for global MHD model. • Solar wind inputs: • Idealized (constant, staggered, jumped, …) • Realistic (usually solar wind plasma and IMF observations) 2002 GEM Student Tutorial

  23. Example of Idealized Solar Wind Input 2002 GEM Student Tutorial

  24. Example of Realistic Solar Wind Input 2002 GEM Student Tutorial

  25. How to Make Global MHD Simulation What do you want to solve? Why do you want to use global model? What results do you expect from a global model? Set model parameters and provide necessary input files Run global model Analyze model results Possible combination with other results (theory, observation) Ready for publication? 2002 GEM Student Tutorial

  26. Visualization 2002 GEM Student Tutorial

  27. Parameter Study 2002 GEM Student Tutorial

  28. Comparison with Observations Solar wind and magnetosphere in situ observations Comparison between model and in situ observations 2002 GEM Student Tutorial

  29. How to Make Global MHD Simulation What do you want to solve? Why do you want to use global model? What results do you expect from a global model? Set model parameters and provide necessary input files Run global model Analyze model results Possible combination with other results (theory, observation) Ready for publication? 2002 GEM Student Tutorial

  30. Publications 2002 GEM Student Tutorial

  31. Outline • Introduction to the Global MHD Simulation • How to perform global MHD Simulation • New Techniques and Challenges 2002 GEM Student Tutorial

  32. Adaptive Mesh Refinement (AMR) Adaptive Mesh Refinement (AMR) N=100 Grids Standard Shock Tube Problem N=1000 Grids 2002 GEM Student Tutorial

  33. AMR (continued) 2002 GEM Student Tutorial

  34. A Movie Showing a Simulation with AMR Click to play the movie! 2002 GEM Student Tutorial

  35. Data Assimilation with Multi-spacecraft Observations 2002 GEM Student Tutorial

  36. Multi-Scale Simulation 2002 GEM Student Tutorial

  37. Other Difficulties and Fronts • Coupling with models with other space regions (even with different physics) • Inward: • Atmosphere, ionosphere and thermosphere models • Ring current and radiation belt models • Outward: • Solar wind models • Difficulties with realistic solar wind inputs • Solar wind Bx problem • Global simulation other than MHD • Simulation with direct coupling of different types of simulations. 2002 GEM Student Tutorial

  38. The Ends 2002 GEM Student Tutorial

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