Steady dust-tail continuity equation
= Steady dust-tail continuity equation
{title2=$n(s)\dot s=\dot N P(t(s))$}
For a single-stream <dust tail> with injection rate $\dot N$, monotone angular distance $s(t)$, and survival probability $P(t)$, the number per unit angle is $n(s)=\dot N P(t(s))/\dot s$. A vanishing angular drift creates an idealized density enhancement; velocity dispersion rounds it.