The small observed scale of AGN--driven outflows, and inside--out disc
  quenching
  Observations of massive outflows with detectable central AGN typically find
them within radii $\lesssim 10$ kpc. We show that this apparent size
restriction is a natural result of AGN driving if this process injects total
energy only of order the gas binding energy to the outflow, and the AGN varies
over time (`flickers') as suggested in recent work. After the end of all AGN
activity the outflow continues to expand to larger radii, powered by the
thermal expansion of the remnant shocked AGN wind. We suggest that on average,
outflows should be detected further from the nucleus in more massive galaxies.
In massive gas--rich galaxies these could be several tens of kpc in radius. We
also consider the effect that pressure of such outflows has on a galaxy disc.
In moderately gas--rich discs, with gas-to-baryon fraction $< 0.2$, the outflow
may induce star formation significant enough to be distinguished from quiescent
by an apparently different normalisation of the Kennicutt-Schmidt law. The star
formation enhancement is probably stronger in the outskirts of galaxy discs, so
coasting outflows might be detected by their effects upon the disc even after
the driving AGN has shut off. We compare our results to the recent inference of
inside--out quenching of star formation in galaxy discs.
