  We present a new model, MULTI-VP, that computes the three-dimensional
structure of the solar wind which includes the chromosphere, the transition
region, and the corona and low heliosphere. MULTI-VP calculates a large
ensemble of wind profiles flowing along open magnetic field-lines which sample
the whole three-dimensional atmosphere or, alternatively, on a given region of
interest. The radial domain starts from the photosphere and extends, typically,
to about 30 $R_{sun}$ . The elementary uni-dimensional wind solutions are based
on a mature numerical scheme which was adapted in order to accept any flux-tube
geometry. We discuss here the first results obtained with this model. We use
Potential Field Source-Surface (PFSS) extrapolations of magnetograms from the
Wilcox Solar Observatory (WSO) to determine the structure of the background
magnetic field. Our results support the hypothesis that the geometry of the
magnetic flux-tubes in the lower corona controls the distribution of slow and
fast wind flows. The inverse correlation between density and speed faraway from
the Sun is a global effect resulting from small readjustments of the flux-tube
cross-sections in the high corona (necessary to achieve global pressure balance
and a uniform open flux distribution). In comparison to current global MHD
models, MULTI-VP performs much faster and does not suffer from spurious
cross-field diffusion effects. We show that MULTI-VP has the capability to
predict correctly the dynamical and thermal properties of the background solar
wind (wind speed, density, temperature, magnetic field amplitude and other
derived quantities) and to approach real-time operation requirements.
