  The astrophysical origin of the r-process nuclei is still unknown. Even the
most promising scenario, the neutrino-driven winds from a nascent neutron star,
encounters severe difficulties in obtaining requisite entropy and short dynamic
timescale for the r-process. In this study, the effect of anisotropy in
neutrino emission from a proto-neutron star surface is examined with
semi-analytic neutrino-driven wind models. The increase of neutrino number
density in the wind owing to the anisotropy is modeled schematically by
enhancing the effective neutrino luminosity. It is shown that the neutrino
heating rate from neutrino-antineutrino pair annihilation into
electron-positron pairs can significantly increase owing to the anisotropy and
play a dominant role for the heating of wind material. A factor of five
increase in the effective neutrino luminosity results in 50% higher entropy and
a factor of ten shorter dynamic timescale owing to this enhanced neutrino
heating. The nucleosynthesis calculations show that this change is enough for
the robust r-process, producing the third abundance peak A = 195 and beyond.
Future multi-dimensional studies with accurate neutrino transport will be
needed if such anisotropy relevant for the current scenario (more than a factor
of a few) is realized during the wind phase (~1-10 s).
