Abstract

We outline the general properties of a disk MHD wind model and its relation to the "blazar divide", namely the distinct spectral properties of the BL Lac and FSRQ Fermi spectra. This model has been applied successfully to account for the X-ray absorption properties of Seyfert galaxies in terms of its global parameters and we contend it can also be applied to provide an account of the blazar spectra. The specific feature of the model that sets it apart from those generally associated with this class of object is that the MHD wind is 2D, with its base on the AGN disk extending to radii of order of 1pc, while its mass flux increases with distance from the AGN along the disk (measured in gravitational radii) like $r^{1/2}$.

The solution of the wind equations produce a 2D density profile which decreases like $1/r$ in the radial direction and normalization that increases xponentially with the polar angle $theta$, to produce a toroidal structure with maximum column along the equator, as demanded by AGN unification. The specific density profile (equal column per decade along any radial direction) guarantees the scattering of sufficient number of central engine soft photons along the jet axis to produce External Compton (EC) dominated gamma-rays, provided that the wind mass flux rate is less than $sim 0.01$ that of Eddington.

We show that the resulting Fermi spectra are consistent with SSC/EC for mass flux rates below/above this critical value for the wind mass flux rate. We compute also the corresponding Halpha luminosity from the entire wind and we find that it also decreases significantly for mass flux rates below this value thus providing the necessary link between optical line and gamma-ray properties of this class of objects.