Magnetic Prandtl number
The Magnetic Prandtl number (Prm) is a dimensionless quantity occurring in magnetohydrodynamics which approximates the ratio of momentum diffusivity (viscosity) and magnetic diffusivity.[1] It is defined as:
where:
- Rem is the magnetic Reynolds number
- Re is the Reynolds number
- ν is the momentum diffusivity (kinematic viscosity)
- η is the magnetic diffusivity
At the base of the Sun's convection zone the Magnetic Prandtl number is approximately 10−2,[2] and in the interiors of planets and in liquid-metal laboratory dynamos is approximately 10−5.