= Alpha-squared dynamo
{title2=$\alpha^2$ dynamo}
An alpha-squared dynamo generates a mean <magnetic field> using an <alpha effect> without requiring an additional large-scale shear coupling. For $\boldsymbol\alpha=\alpha_0\operatorname{diag}(1,1,0)$ and a transverse mean field varying as $e^{iKz}$, the growth rates are $-\eta K^2\pm\alpha_0K$. A nonzero $\alpha_0$ therefore allows growth for sufficiently long wavelengths, provided the domain and scale separation permit them.
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