Magnetic diffusivity

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:

$\eta = \frac{1}{\mu_0 \sigma_0}$,

where $\mu_0$ is the permeability of free space 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: $\sigma_0=\frac{n_ee^2}{m_e\nu_c}$, 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