Must Haves

1. As realistic parameter values as possible
2. Boundary conditions:
   1. Temperature: Dirichlet, Neumann or Robin conditions at either boundary
   2. Tangential Velocity: No slip or viscous stress-free or drag laws, e.g. general Rayleigh friction, Ekman friction
   3. Magnetic Field: Finitely or perfectly conducting or insulating at both boundaries, CMB: specify conductance of layer instead of conductivity for a weakly conducting layer
   4. Radial velocity: impermeable, drag laws, prescribable
3. Initial Conditions on B,v,T:
   1. present day B field
   2. weak or strong B field
   3. benchmark case
   4. dipolar or multipolar B field
   5. gravity fields?
   6. ability to change resolution in initial file
4. Geometry:
   1. Prescription of inner core size, including no inner core
   2. Topography on boundaries using small slope approximation
5. External Influences:
   1. Mantle thermal heterogeneities as a thermal boundary condition
   2. External magnetic field sources
6. Driving Mechanisms:
   1. Internal heating
   2. Compositional driving independent of thermal driving
7. Stratification:
   1. Allowing radial stratification through background temperature profiles (i.e. fake heat sources in Boussinesq models)
   2. Prescribed radial variations of internal heat sources, secular cooling, and compositional change (note: this is a generalization of item 5a).
8. Temperature/pressure dependent physical parameters
   1. Different equations of state
   2. Radial variations (e.g. density, conductivity, viscosity…)
9. Freely Rotating Inner core that can respond to torques from:
   1. Inner-core / Mantle gravitational coupling
   2. EM torques
   3. Viscous torques
10. Explicit treatment of Coriolis force

“Easy” Additions

1. Driving Mechanisms:
   1. Precession, Tides, Mechanical torques
2. Stratification:
   1. Internal interfaces through continuity conditions
3. Implicit treatment of Coriolis force
4. Subgrid-scale turbulence
5. Gravity field solver (including mantle density anomalies)
6. Radiative regions in gas giant atmospheres

Dream of having

1. Even more realistic parameter values than currently possible
2. Real geochemistry in the core
   1. snow zones
   2. helium rain
   3. other odd features due to chemistry in multi-component fluids
   4. geochemical reactions with the mantle at the CMB
   5. solid/fluid mixtures
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. Real geochemistry in the core
   1. snow zones
   2. helium rain
   3. other odd features due to chemistry in multi-component fluids
5. Mushy layer physics at ICB
6. Solid/fluid mixtures
7. Boundary conditions:
   1. tangential velocity field: magnetoviscous friction
   2. radial velocity: permeable
   3. time-varying inner core radius
8. Laterally variable temperature/pressure dependent physical parameters (e.g relating conductivity directly to temperature in Hot Jupiter atmospheres)