Identification of the coronal sources of the fast solar wind

The present spectroscopic study of the ultraviolet coronal emission in a po lar hole, detected on 1996 April 6-9 with the Ultraviolet Coronagraph Spect rometer aboard the Solar and Heliospheric Observatory spacecraft, identifie s the interplume lanes and background coronal hole regions as the channels in which the fast solar wind is preferentially accelerated. In interplume l anes, at heliocentric distance 1.7 R., the corona expands at a rate between 105 and 150 km s(-1), that is, much faster than in plumes in which the out flow velocity is between 0 and 65 km s(-1). The wind velocity is inferred f rom the Doppler dimming of the O VI lambda lambda 1032, 1037 lines, within a range of values, whose lower and upper limit corresponds to anisotropic a nd isotropic velocity distribution of the oxygen coronal ions, respectively .