These equations are then non-dimensionalized, introducing the non-dimensional parameters, R a = g α α T D 3 ν ν κ κ , E = ν ν Ω Ω D 2 , P r = ν ν κ κ , P m = ν ν η η where R a is the Rayleigh number, E the Ekman number, P r and P m the Prandtl and magnetic Prandtl number. Magnetic field scaling is often in Elsasser number units B = ( ρ ρ Ω Ω / σ σ ) 1 / 2 .