Must Haves

1. Boundary conditions:
   1. Temperature: Fixed temp or fixed flux at both boundaries
   2. Tangential Velocity: No slip or viscous stress-free or drag law
   3. Magnetic Field: Finitely conducting or insulating at both boundaries
   4. Radial velocity: impermeable or permeable
2. Geometry:
   1. Prescription of inner core size, including no inner core
   2. Topography on boundaries (e.g. ellipticity, or mountains)
3. External Influences:
   1. Mantle thermal heterogeneities as a thermal boundary condition
   2. External magnetic field sources
4. Driving Mechanisms:
   1. Internal heating
   2. Compositional driving independent of thermal driving
   3. Precession, Tides, Mechanical torques (i.e. impacts, boundary motion)
5. Stratification:
   1. Allowing radial stratification through background temperature profiles (i.e. fake heat sources in Boussinesq models)
   2. Internal interfaces
   3. Prescribed radial variations of internal heat sources, secular cooling, and compositional change (note: this is a generalization of item 5a).
6. Temperature/pressure dependent physical parameters
   1. Different equations of state
   2. Radial variations (e.g. density, conductivity, viscosity…)
   3. Lateral variations (e.g. relating conductivity directly to temperature in Hot Jupiter atmospheres)
   4. allowing radiative regions in gas giant atmospheres
7. Freely Rotating Inner core that can respond to torques from:
   1. Inner-core / Mantle gravitational coupling
   2. EM torques
   3. Viscous torques
   4. Pressure torques (with boundary topography)
8. Implicit or explicit treatment of Coriolis force

Dream of having

1. As realistic parameter values as possible
2. Subgrid-scale turbulence (perhaps this should go in the “must haves” based on Hiro’s & Bruce’s work?)
3. Inner core physics
   1. convection in the inner core
   2. inner core translation
   3. phase equilibrium at inner core boundary
   4. inner core ellipticity – respond to gravitational torques in mantle
4. Gravity field solver (including mantle density anomalies)
5. Real geochemistry in the core
   1. snow zones
   2. helium rain
   3. other odd features due to chemistry in multi-component fluids
   4. mixtures of solids & fluids
6. Mushy layer physics at ICB
7. Solid/fluid mixtures