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:
where is the permeability of free space and is the electrical conductivity of the material in question. In case of a plasma, this is the conductivity due to Coulomb or neutral collisions: , where
- is the electron density.
- is the electron charge.
- is the electron mass.
- is the collision frequency.
- ^ W. Baumjohann and R. A. Treumann, Basic Space Plasma Physics, Imperial College Press, 1997.