Scatter plots between the IRIS SJI 2832 Å intensity and the HMI magnetic field strength. The format is similar to Fig. 5. The IRIS SJI 2832 Å intensity and magnetic field strength histograms are shown above and to the right, respectively, of each scatter plot. The black and light blue plots indicate respectively the results from the oscillation centers and the whole umbra defined by the inside of the ellipse in Fig. 6a. The IRIS SJI 2832 Å intensity is plotted in a logarithmic scale.