tokens: of 3°–14°. Figure 10. Top panel: Wind simulation with parameter values set to match P04: f x = 0.1, R in = 60 R g , cm/s, T = 2.5 × 10 4 K, and n 0 = 2.5 × 10 9 cm −3 . We also set τ UV = 0, and σ X = σ T as it is done in P04. Bottom panel: Wind simulation with same parameters as the top panel but using the standard τ UV and τ X of Qwind . 4 CONCLUSIONS AND FUTURE WORK We have presented an updated version of the Qwind code ( Qwind2 ), aimed at modelling the acceleration phase of UV line-driven winds in AGNs. The consistency of our approach with other more sophisticated simulations shows that the non-hydrodynamical treatment is well justified, and that our model has the potential to mimic the results of more expensive hydrodynamical simulations. The main free parameters of the model are the initial density and velocity of each streamline, and the inner disc radius from which the fluid elements are first launched. Nomura et al. ( 2013 ) calibrate the initial wind mass loss using the relation from CAK that links the wind mass loss from O-stars to their gravity and Eddington ratio. However, it is not clear whether this relation holds for accretion discs, where the geometry and the radiation field and sources are quite different (Laor Davis 2014 ). To be able to derive these initial wind conditions from first principles, we require a physical model of the vertical structure of the accretion disc. Furthermore, we need to take into account the nature of the different components of the AGN and their impact on the line-driving mechanism. In that regard, we can use spectral models like Kubota Done ( 2018 ) to link the initial conditions and physical properties of the wind to spectral features. We aim to present in an upcoming paper a consistent physical model of the vertical structure of the disc, considering the full extent of radiative opacities involved, that will allow us to infer the initial conditions of the wind. Another point that needs to be improved is the treatment of the radiation transfer. Qwind and current hydrodynamical simulations compress all of the information about the SED down to two numbers L X and L UV; however, the wavelength-dependent opacity can vary substantially across the whole spectrum. This simplification is likely to underestimate the level of ionization of the wind (Higginbottom et al. 2014 ) and motivates the coupling of Qwind to a detailed treatment of radiation transfer. Higginbottom et al. ( 2013 ) construct a simple disc wind model with a Monte Carlo ionization/radiative transfer code to calculate the UV spectra as a function of viewing angle; however, properties of the wind such as its mass flow rate and the initial radius of the escaping trajectories need to be assumed. We will incorporate a full radiative transfer code like Cloudy or Xstar to compute the line driving and transmitted spectra together. This also opens the possibility of having a metallicity-dependent force multiplier and studying how the wind
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