Planetary Dynamos

Planetary Dynamos

College of Science and Engineering via YouTube Direct link

Coefficients = Dynamical Variables

17 of 25

17 of 25

Coefficients = Dynamical Variables

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Planetary Dynamos

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  1. 1 Planetary Dynamos
  2. 2 Planetary Magnetospheres
  3. 3 Planetary Auroras are one indication of a magnetic dipole field
  4. 4 Internal Dynamo in a Liquid Core Generates the Main Planetary Magnetic Field
  5. 5 Planetary Data
  6. 6 (Some) Geodynamo Researchers
  7. 7 Interior of the Earth
  8. 8 The Earth’s Inner Core
  9. 9 Geological Record: Geomagnetic Excursions
  10. 10 Basic Equations Mathematical model based on the magnetohydrodynamic (MHD) equations with buoyancy → the 'Boussinesq approximation : compositional variation is not included because of strong mixing.
  11. 11 Numerical Modeling Solve nonlinear partial differential equations (PDEs) on computer. Various methods: finite difference, finite volume,.... For regular geometries, we can choose a spectral method
  12. 12 Geodynamo Parameters
  13. 13 Magnetic Fields Turbulent relaxation of ideal magneto-fluid
  14. 14 Spectral Method Model
  15. 15 Spherical Harmonics
  16. 16 Function Expansions for Spherical Shells
  17. 17 Coefficients = Dynamical Variables
  18. 18 A Dynamical System The spectral method tums a few PDEs into many coupled ODES
  19. 19 Statistics of Ideal MHD Turbulence
  20. 20 Probability Density Function (PDF) The invariants for ideal MHD are
  21. 21 Expectation Values
  22. 22 Cross Helicity, HC He is essentially the cross correlation between velocity and magnetic field in the liquid core.
  23. 23 Expected Dipole Angle 0 vs Cross Helicity Hc The dipole angle can be calculated using the statistical theory, with maximum , i, m = 100 Large-scale numerical simulations of ideal, rotating MHD turbul…
  24. 24 Summary: The Ideal MHD Geodynamo
  25. 25 Conclusion

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