Alpha effect
= Alpha effect
{title2=$\boldsymbol{\mathcal E}=\boldsymbol\alpha\overline{\mathbf B}$}
The alpha effect is the part of a <mean-field electromotive force> linear in the mean <magnetic field> itself, $\boldsymbol{\mathcal E}=\boldsymbol\alpha\overline{\mathbf B}+\cdots$. The <alpha tensor> can be anisotropic; it need not be a scalar multiple of the identity. Its <curl> can couple transverse mean-field components and produce an <alpha-squared dynamo>.