= Magnetostrophic balance
{title2=$2\rho\Omega\hat z\times u=-\nabla p+f_b+J\times B$}
The leading <force balance> in a rapidly rotating conducting <fluid> when inertial and viscous forces are small, while <Coriolis force>, <pressure>, <buoyancy> and <Lorentz force density> remain significant. The <Rossby number> and <Ekman number> measure the omitted inertia and <bulk viscosity>. <Rotation> does not balance an arbitrary magnetic torque: impenetrable axisymmetric boundaries impose the <Taylor constraint>. <Magnetic diffusion> can remain in the induction equation even when <viscosity> is neglected in <momentum> balance.
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