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Active region (AR) outflows have been studied in detail since the launch of\textit{Hinode}/EIS and are believed to provide a possible source of mass andenergy to the slow solar wind. In this work, we investigate the loweratmospheric counterpart of AR outflows using observations from the\textit{Interface Region Imaging Spectrograph} (\textit{IRIS}). We find thatthe \textit{IRIS} \siiv, \cii\ and \mgii\ transition region (TR) andchromospheric lines exhibit different spectral features in the outflows ascompared to neighboring regions at the footpoints ("moss") of hot AR loops. Theaverage redshift of \siiv\ in the outflows region ($\approx$ 5.5~km s$^{-1}$)is smaller than typical moss ($\approx$ 12--13 km~s$^{-1}$) and quiet Sun($\approx$ 7.5 km~s$^{-1}$) values, while the \cii~line is blueshifted($\approx$ -1.1--1.5 km~s$^{-1}$), in contrast to the moss where it is observedto be redshifted by about $\approx$ 2.5 km~s$^{-1}$. Further, we observe thatthe low atmosphere underneath the coronal outflows is highly structured, withthe presence of blueshifts in \siiv\ and positive \mgii\ k2 asymmetries (whichcan be interpreted as signatures of chromospheric upflows) which are mostly notobserved in the moss. These observations show a clear correlation between thecoronal outflows and the chromosphere and TR underneath, which has not beenshown before. Our work strongly suggests that these regions are not separateenvironments and should be treated together, and that current leading theoriesof AR outflows, such as the interchange reconnection model, need to take intoaccount the dynamics of the low atmosphere.

IRIS observations of the low-atmosphere counterparts of active region outflows