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:W. Baumjohann and R. A. Treumann, ''Basic Space Plasma Physics'', Imperial College Press, 1997.
:$\eta = \frac$,
while in Gaussian units it can be defined as
:$\eta = \frac$.
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: $\sigma_0=\frac$, 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

Plasma physics

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