Twenty-five RPs (solid black lines) from the k-means clustering of the Hε line that are identified as a signature of QSEB. The k-means clustering was performed for 13 line positions around the Hε nominal line core. The shaded colored areas represent the density distribution of Hε spectra within a cluster. The dotted black line shows the Hε profile that is farthest (measured in Euclidean distance) from the corresponding RP within a particular cluster. The average quiet-Sun profile (gray line) is plotted in each panel as reference. The parameter n represents the number of spectral profiles in a cluster as the percentage of the total of ∼1.7 × 10⁹ spectra.