  Ultraviolet observations of classical T Tauri Stars (cTTSs) have shown that
there is a hot (Te ~ 80,000 K) and dense (ne ~ 1e10 cm-3) component associated
with the large scale jet. This hot component is formed very close to the base
of the jet providing fundamental information on the jet formation mechanism. In
this series, we have investigated whether this component can be formed in disc
winds, either cool or warm. To conclude the series, jet launching from the
interface between the magnetic rotor (the star) and the disc is studied.
Synthetic profiles are calculated from numerical simulations of outflow
launching by star-disc interaction. Profiles are calculated for several
possible configurations of the stellar field: dipolar (with surface strengths,
B of 1, 2 and 5 kG) or dynamo fed. Also two types of discs, passive or
subjected to an alpha/Omega-dynamo, are considered. These profiles have been
used to define the locus of the various models in the observational diagram:
dispersion versus centroid, for the profiles of the SiIII] line. Bulk motions
produce an increasing broadening of the profile as the lever arm launching the
jet becomes more efficient; predicted profiles are however, sensitive to the
disc inclination. Models are compared with observations of the SiIII] lines
obtained with the Hubble Space Telescope.
  In addition, it is shown that the non-stationary nature of star-disc winds
produce a flickering of the profile during quiescence with variations in the
line flux of about 10%. At outburst, accretion signatures appear in the
profiles together with an enhancement of the wind, producing the correlation
between accretion and outflow as reported from RU Lup, AA Tau and RW Aur
observations.
