  The origin of the slow solar wind is still an open issue. It has been
suggested that upflows at the edge of active regions (AR) can contribute to the
slow solar wind. Here, we compared the upflow region and the AR core and
studied how the plasma properties change from the chromosphere via the
transition region to the corona. We studied limb-to-limb observations NOAA
12687 (14th - 25th Nov 2017). We analysed spectroscopic data simultaneously
obtained from IRIS and Hinode/EIS in six spectral lines. We studied the mutual
relationships between the plasma properties for each emission line, as well as
comparing the plasma properties between the neighbouring formation temperature
lines. To find the most characteristic spectra, we classified the spectra in
each wavelength using the machine learning technique k-means. We found that in
the upflow region the Doppler velocities of the coronal lines are strongly
correlated, but the transition region and coronal lines show no correlation.
However, their fluxes are strongly correlated. The upflow region has lower
density and lower temperature than the AR core. In the upflow region, the
Doppler and non-thermal velocity show a strong correlation in the coronal
lines, but the correlation is not seen in the AR core. At the boundary between
the upflow region and the AR core, the upflow region shows an increase in the
coronal non-thermal velocity, the emission obtained from the DEM, and the
domination of the redshifted regions in the chromosphere. The obtained results
suggest that at least three parallel mechanisms generate the plasma upflow: (1)
the reconnection between closed loops and open magnetic field lines in the
lower corona or upper chromosphere; (2) the reconnection between the
chromospheric small-scale loops and open magnetic field; (3) the expansion of
the magnetic field lines that allows the chromospheric plasma to escape to the
solar corona.
