 Mean-field electromotive force

The mean-field electromotive force is the vector correlation $\mathcal{E}=⟨\mathbf{u}\times \mathbf{b}⟩$. Its curl enters the mean resistive induction equation. It is a local vector with units of velocity times magnetic field, not the scalar circuit voltage called electromotive force. A space-time average of periodic modes is often used to measure its transport coefficients.