  The origin of the solar wind is one of the most important unresolved prob-
lems in space and solar physics. We report here the first spectroscopic
signatures of the nascent fast solar wind on the basis of observations made by
the EUV Imaging Spectrometer (EIS) on Hinode in a polar coronal hole, in which
patches of blueshift are clearly present on dopplergrams of coronal emission
lines with a formation temperature of lg(T/K)=6.0. The corresponding upflow is
associated with open field lines in the coronal hole, and seems to start in the
solar transition region and becomes more prominent with increasing temperature.
This temperature-dependent plasma outflow is interpreted as evidence of the
nascent fast solar wind in the polar coronal hole. The patches with significant
upflows are still isolated in the upper transition region but merge in the
corona, in agreement with the scenario of solar wind outflow being guided by
expanding magnetic funnels.

Solar and Stellar Astrophysics