Mag_Reynolds

plasmapy.formulary.Mag_Reynolds(U: Unit(‘m / s’), L: Unit(‘m’), sigma: Unit(‘S / m’))

Compute the magnetic Reynolds number

The magnetic Reynolds number is a dimensionless quantity that estimates the relative contributions of advection and induction to magnetic diffusion in a conducting medium.

\[Rm = \frac{U L}{η}\]

where \(η = \frac{1}{μ_0 σ}\) and \(μ_0\) is the permeability of free space.

Aliases: Rm_

Parameters

• U (Quantity) – The velocity scale of the plasma.

• L (Quantity) – The length scale of the plasma.

• sigma (Quantity) – The conductivity of the plasma.

Warns

UnitsWarning – If units are not provided, SI units are assumed.

Raises

• TypeError – If U is not a Quantity and cannot be converted into a Quantity.

• UnitConversionError – If U is not in appropriate units.

Examples

>>> import astropy.units as u
>>> sigma = 5.96e7 * u.S / u.m
>>> U = 10 * u.m / u.s
>>> L = 1 * u.cm
>>> Mag_Reynolds(U, L, sigma)
<Quantity 7.48955689>
>>> rho = 1e-8 * u.S / u.m
>>> U = 0.1 * u.m / u.s
>>> L = 0.05 * u.m
>>> Mag_Reynolds(U, L, sigma)
<Quantity 0.37447784>

Returns

Rm – The magnetic Reynolds number.

Return type

Quantity