  Recent observations from Parker Solar Probe have revealed that the solar wind
has a highly variable structure. How this complex behaviour is formed in the
solar corona is not yet known, since it requires omnipresent fluctuations,
which constantly emit material to feed the wind. In this article we analysed 14
upflow regions in the solar corona to find potential sources for plasma flow.
The upflow regions were derived from spectroscopic data from the EUV Imaging
Spectrometer (EIS) onboard Hinode determining their Doppler velocity and
defining regions which have blueshifts stronger than $-6\,km\,s^{-1}$. To
identify the sources of this blueshift data from the Atmospheric Imaging
Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), onboard the
Solar Dynamics Observatory (SDO), and the X-ray Telescope (XRT), onboard
Hinode, were used. The analysis revealed that only 5 out of 14 of the upflows
were associated with frequent transients, like obvious jets or bright points.
In contrast to that, seven events were associated with small-scale features,
which show a large variety of dynamics. Some resemble small bright points,
while others show an eruptive nature, all of which are faint and only live for
a few minutes; we can not rule out that several of these sources may be fainter
and, hence, less obvious jets. Since the complex structure of the solar wind is
known, this suggests that new sources have to be considered or better methods
used to analyse the known sources. This work shows that small and frequent
features, which were previously neglected, can cause strong upflows in the
solar corona. These results emphasise the importance of the first observations
from the Extreme-Ultraviolet Imager (EUI) onboard Solar Orbiter, which revealed
complex small-scale coronal structures.
