 Inward transport by an angular-momentum-enhanced disk wind

For zero viscosity, $S=f(r)\Sigma$ and constant $q>1$, set $\beta =2(q-1)$. On intervals where f>0, the wind-loaded Keplerian disk evolution equation becomes ${\Sigma }_t=\beta rf{\Sigma }_r+[\beta (2f+r{f}^{\prime })-f]\Sigma$. Multiplication by $f{r}^{2-1/\beta }$ and the displayed travel-time coordinate reduce it to constant-speed advection. Its profile is $g^{\prime }=F(x^{\prime }+t)$ and its characteristics move inward with $dr/dt=-\beta rf$. The weight accounts for mass loss as well as radial compression.