Reynolds number (for a magnetic field)
The magnetic Reynolds number is the magnetic analogue of the Reynolds number, a fundamental dimensionless group that occurs in magnetohydrodynamics. It gives an estimate of the relative effects of advection or induction of a magnetic field by the motion of a conducting medium, often a fluid, to magnetic diffusion.
The mechanism by which the motion of a conducting fluid generates a magnetic field is the subject of dynamo theory. When the magnetic Reynolds number is very large, however, diffusion and the dynamo are less of a concern, and in this case focus instead often rests on the influence of the magnetic field on the flow.Related formulas
|Rm||magnetic Reynolds number (dimensionless) (dimensionless)|
|U||typical velocity scale of the flow (m/s)|
|L||ypical length scale of the flow (m)|
|η||magnetic diffusivity (m2/s)|