Can warm absorbers be driven by ultra-fast outflows?
  Warm absorbers (WAs) located approximately in the region of $1-1000$ parsecs
are common phenomena in many active galactic nuclei (AGNs). The driving
mechanism of WAs is still under debate. Ultra-fast outflows (UFOs) which are
launched very close to the central black hole are also frequently observed in
AGNs. When UFOs move outwards, they will collide with the interstellar medius
(ISM) gas. In this paper, we study the possibility that whether WAs can be
generated by the interaction between ISM gas and the UFOs. We find that under
some ISM gas conditions, WAs can be generated. However, the covering factor of
WAs is much smaller than that given by observations. This indicates that other
mechanisms should also be at work. We also find that the properties of the WAs
mainly depend on the density of the ISM injected into the computational domain
from the outer radial boundary (1000 parsec). The higher the density of the ISM
is, the higher the mass flux and kinetic power of the WAs will be. The kinetic
power of the UFO driven WAs is much less than $1\%$ of the bolometric
luminosity of its host AGNs. Therefore, the UFO driven WAs might not contribute
sufficient feedback to its host galaxy.
