  From 2022 March 18-21, active region (AR) 12967 was tracked simultaneously by
Solar Orbiter (SO) at 0.35 au and Hinode/EIS at Earth. During this period,
strong blue-shifted plasma upflows were observed along a thin, dark corridor of
open field originating at the AR's leading polarity and continuing towards the
southern extension of the northern polar coronal hole. A potential field source
surface (PFSS) model shows large lateral expansion of the open magnetic field
along the corridor. Squashing factor Q-maps of the large scale topology further
confirm super-radial expansion in support of the S-Web theory for the slow
wind. The thin corridor of upflows is identified as the source region of a slow
solar wind stream characterised by approx. 300 km s-1 velocities, low proton
temperatures of approx. 5 eV, extremely high density over 100 cm-3, and a short
interval of moderate Alfvenicity accompanied by switchback events. When
connectivity changes from the corridor to the eastern side of the AR, the in
situ plasma parameters of the slow wind indicate a distinctly different source
region. These observations provide strong evidence that the narrow open field
corridors, forming part of the S-Web, produce extreme properties in their
associated solar wind streams.
