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:^[1]

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

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

References

1. W. Baumjohann and R. A. Treumann, Basic Space Plasma Physics, Imperial College Press, 1997.