= Midplane tilt contribution to asymmetric drift
{title2=$-R\partial_z\overline{v_Rv_z}|_{z=0}$}
Reflection symmetry makes $\overline{v_Rv_z}$ odd in height, so its value at the midplane vanishes while its derivative need not vanish. The radial <Jeans equation> includes this derivative in the <stellar asymmetric drift>. For a <velocity ellipsoid> locally aligned with spherical coordinates, $\overline{v_Rv_z}\simeq(\sigma_R^2-\sigma_z^2)z/R$, and its midplane contribution is $-(\sigma_R^2-\sigma_z^2)$. Dropping a mixed moment at the symmetry plane does not justify dropping its derivative.
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