  Mid-resolution spectra are used to deduce the size and kinematics of the
coronal gas in a sample of Seyfert galaxies by means of observations of the
[FeXI], [FeX], [FeVII], [SiVI] and [SiVII] lines. These coronal lines (CL)
extend from the unresolved nucleus up to a few tens to a few hundreds of
parsecs. The region of the highest ionized ions studied, [FeXI] and [FeX], is
the least spatially extended, and concentrates at the center; intermediate
ionization lines extend from the nucleus up to a few tens to a few hundred
parsecs; lower [OIII]-like ions are known to extendin the kpc range. All
together indicates a stratification in the ionized gas, usually interpreted in
terms of nuclear photoionization as the driving ionization mechanism. However,
CL profiles show various peculiarities: they are broader by a factor of two
than lower ionization lines, the broadening being in terms of asymmetric blue
wings, and their centroid position at the nucleus is blueshifted by a few
hundreds of km/s. Moreover, in NGC1386 and NGC1068, a double peak [FeVII] line
is detected in the nuclear and extended coronal region, this being the first
report in of such type of profile in CL in active galactic nuclei. If
interpreted as outflow signatures, the total broadening of the lines at zero
intensity levels implies gas velocities up to 2000 km/s. Although the
stratification of ions across the coronal region means that photoionization is
the main power mechanism, the high velocities deduced from the profiles, the
relatively large spatial extension of the emission, and the results from
photoionization models indicate that an additional mechanism is at work. We
suggest that shocks generated by the outflow could provide the additional
required power for line formation.
