Alpha tensor (${\alpha }_{ij}$)

The alpha tensor is the linear map from a uniform test magnetic field to the corresponding mean-field electromotive force. Its components satisfy ${\mathcal{E}}_i={\alpha }_{ij}{B}_{0j}$. Anisotropic helical flows can produce a real symmetric rank-two response, such as ${\alpha }_0\mathrm{diag}(1,1,0)$.