Physics:Magnetic diffusivity

Short description: A parameter in plasma physics

The magnetic diffusivity is a parameter in plasma physics which appears in the magnetic Reynolds number. It has SI units of m²/s and is defined as:

$\eta =\frac{1}{{\mu }_0{\sigma }_0}$,

while in Gaussian units it can be defined as

$\eta =\frac{c^2}{4\pi {\sigma }_0}$.

In the above, ${\mu }_0$ is the permeability of free space, $c$ is the speed of light, and ${\sigma }_0$ is the electrical conductivity of the material in question. In case of a plasma, this is the conductivity due to Coulomb or neutral collisions: ${\sigma }_0=\frac{n_e{e}^2}{m_e{\nu }_c}$, where

• $n_e$ is the electron density.
• $e$ is the electron charge.
• $m_e$ is the electron mass.
• ${\nu }_c$ is the collision frequency.

See also

• Electrical resistivity and conductivity