Chromospheric activity at base of jet. Maps of the intensity [DN] at three wavelength points along the Mg II line are shown in the top row. The wavelength locations are: (a) k3: 2796.37 Å, (b) k2r: 2796.52 Å, and (c) k1r: 2796.78 Å. Each map shares the same axis-scaling, spatial extent, and pixel markers as that in Fig. 4. Mg II k spectra from these pixels are shown in the bottom four rows, panels d–g. The black curve in each panel shows the same normalized, average intensity profile for Mg II for this observation, calculated using a large portion of quiet Sun. The k3, k2r, and k1r wavelength points were selected based on the shape of this profile and are marked by the vertical solid, dotted, and dashed lines, respectively. The k2v peak of this curve is used as the normalization factor for both the averaged profile and the individual pixel profiles (red curves). See Sect. 3.2.