Structure of Protoplanetary Discs with Magnetically-driven Winds
  We present a new set of analytical solutions to model the steady state
structure of a protoplanetary disc with a magnetically-driven wind. Our model
implements a parametrization of the stresses involved and the wind launching
mechanism in terms of the plasma parameter at the disc midplane, as suggested
by the results of recent, local MHD simulations. When wind mass-loss is
accounted for, we find that its rate significantly reduces the disc surface
density, particularly in the inner disc region. We also find that models that
include wind mass-loss lead to thinner dust layers. As an astrophysical
application of our models, we address the case of HL Tau, whose disc exhibits a
high accretion rate and efficient dust settling at its midplane. These two
observational features are not easy to reconcile with conventional accretion
disc theory, where the level of turbulence needed to explain the high accretion
rate would prevent a thin dust layer. Our disc model that incorporates both
mass-loss and angular momentum removal by a wind is able to account for HL Tau
observational constraints concerning its high accretion rate and dust layer
thinness.
