Schematic view of the thermally and dynamically inhomogeneous outer atmosphere of Arcturus. The structure of the chromospheric region is based on Fig. 6 of Ayres et al. (2003). The authors postulated that closed magnetic loops (shown in violet), which are responsible for the hot coronal gas, are submerged in the chromospheric gas at lower temperatures (shown in blue). The locations of the two CO layers are based on our modeling. While we adopted two discrete CO layers in our modeling, it is possible that the actual density distribution of this cool molecular component is continuous. This is represented by the pale green region between the inner and outer CO layers as well as between the photosphere and the inner CO layer.