 magnetic Reynolds number

▪ physicscombination of quantities that indicates the dynamic behaviour of a plasma. This number is analogous to the Reynolds number of ordinary fluid mechanics, which is used to determine whether or not a fluid flow will smooth out or become turbulent. If the magnetic permeability of free space is represented by μ_{0} (a constant of proportionality used in expressing the force between two electric charges), the electrical conductivity of the plasma is represented by σ, the plasma velocity by V, and a length characteristic of the plasma structure is L, then the magnetic Reynolds number equals their product, or R_{m} = μ_{0}σVL.According to the magnetohydrodynamic (magnetohydrodynamics) description of the plasma, there are two general types of behaviour for the magnetic field depending upon the value of R_{m}. If R_{m} is much smaller than 1, the magnetic field will diffuse away, and inhomogeneities in the field will be smoothed out, as in the flow of a fluid smoothing out. If R_{m} is very large, the magneticfield lines tend to remain “frozen” into the plasma, moving along with the plasma flow.
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Universalium. 2010.