70 Years of Magnetospheric Modeling A Tutorial George Siscoe Center for Space Physics Boston University Preliminaries • Historical Approach • Five Model Uses 1. Models that Represent Empirical and AI 2. Models that Explain Modular 3. Models that Reveal Kinetic and MHD 4. Models that Interpret All Types 5. Models that Predict All Types • This Talk Considers only Modular and MHD Models that Explain and Reveal Outline •Three Approaches 1. Modular 2. Regional MHD 3. Global MHD • Future Directions Modular 1930s: Inception of Chapman-Ferraro model Midgley and Davis 1963 Mead 1964 Early ‘60s: Culmination of the C-F project Midgley and Davis 1963 Mead 1964 Mid ‘60s: Discovery of the tail and the magnetosheath Midgley and Davis 1963 Ness 1965 Fairfield 1968 Summary of Chapman-Ferraro Epoch: • Well posed, fully explicit formulation • Analytic solutions possible • Size & shape of the magnetopause found • Dependence on S/W ram pressure found • Dependence on dipole tilt found • Global force balance understood • But downhill from here • No storms • Empty tail • No magnetosheath Modular Magnetosheath: Spreiter & Co. Luhmann et al., 1984 Modules for the closed tail: • Current specification • C-F approach • Prescribed magnetopause • Analytic tail approximation • Convection added Modular Current Specification Olson and Pfitzer 1974 Bird 1979 Mead and Williams 1965 Chapman-Ferraro approach to modeling the closed tail Siscoe 1966 Spreiter and Alksne 1969 Unti and Atkinson 1968 Prescribed magnetopause approach to modeling the closed tail Voigt stretch model Schulz source surface model Schulz source surface model Analytic tail approximations and convection: The Birn-Schindler project Summary of Closed-Tail Epoch: • Ill posed but fully explicit formulations • Results depend on assumptions and approach • Analytic solutions still possible but superceded by computational solutions • Global force balance understood • Magnetotail B-field modeled • In particular, Bz dependence on x modeled • Dipole tilt geometry modeled • Polar cap geometry and tilt dependence modeled • Role of field-aligned currents discovered • “Convection time dependence” discovered • Modules for open tail models developed • Initial state for regional MHD model developed • But still no solar wind coupling • No convection electric field Modules for the Open Magnetosphere: • The Stern-singularity problem • The Toffoletto-Hill solution • Region 1 current modeling • The SSM (Peroomian) extension The Stern-singularity problem Siscoe 1988 E parallel T-H and SSM compared T-H SSM (P) Region 1 Currents: SSM (P) Peroomian et al. 1991 Siscoe et al. 1991 Summary of Open-Tail Epoch: • Ill posed but fully explicit formulations • Results depend on assumptions and approach • Analytic solutions still possible but superceded by computational solutions • Magnetotail B-field modeled • Polar cap potential modeled • Stern singularity overcome in TH not in SSM • Region 1 currents in SSM not in TH • No plasma • No physics for field-aligned currents Vasyliunas 1970 Jaggi & Wolf 1973 Magnetosphere-Ionosphere Coupling Modules Rice Convection Model (RCM) The Wolf & Co. project RCM Master Plan RCM + UCLA MHD Code (Toffoletto 2000) Summary of MI Coupling Epoch: • Well posed fully explicit • Analytic solutions possible superceded by computations • Assumed potential and plasma at boundaries • Inner magnetosphere plasma modeled • Physical region 2 currents • No region 1 currents • First RCM-MHD results Equilibrium RCM Toffoletto 2000 Regional MHD Plasmoid Kelvin-Helmholtz wave Flux transfer event Plasmoid Simulation Lee et al. 1985 Kelvin-Helmholtz Simulation Otto & Fairfield 2000 FTE Simulation Scholer 1989 Global MHD • Open geometry • Magnetospheric sash • E-Parallel & reconnection Open Geometry Raeder GGCM Web Site Magnetospheric Sash 0 -10 -5 -2 2 4 X=6 IMF -1 1 3 5 IMF + -5 -10 + + X=7 + + 6 X=8 IMF 4 2 0 -5 -10 E-Parallel & Reconnection Future Directions Hybrids Other Magnetospheres Deep Questions Acknowledgements Bill White Keith Siebert Dan Weimer Bengt Sonnerup Nelson Maynard Gary Erickson NSF NASA DTRA