= Lehnert number
{c}
{title2=$\mathrm{Le}=v_A/(\Omega L)$}
The <Lehnert number> compares an <Alfvén speed> to a <rotation> speed on <length> scale $L$. With $\mathrm{Le}\ll1$, magnetic-wave <frequencies> are small compared with the <rotation> <frequency>, allowing nearly <geostrophic flow>. Ideal weakly damped magnetic waves also require $\eta/L^2$ and $\nu/L^2$ to be small compared with their wave <frequency>; a small <Lehnert number> alone does not guarantee weak diffusion.
Back to article page
