Comparison of a simulated and an observed EB in He I 10 830 Å and He I D₃. Top two rows: He I D₃ images and spectra, and lower two rows: He I 10 830 Å images and spectra. Left column: synthetic data at μ = 1, middle column: synthetic data at μ = 0.27, and right column: observed data at μ = 0.27. The He I D₃ observed image is normalized by the local continuum. The red and blue squares in the images indicate the position of the spectra that are displayed in the corresponding color in the panel below the image. The white square corresponds to the black profile. The He I 10 830 Å observed spectral region also contains a Si I line at v_LOS ∼ −85 km s⁻¹ and two telluric lines at v_LOS ∼ 50 km s⁻¹ and v_LOS ∼ 100 km s⁻¹. The vertical black lines on the spectra indicate the wavelength position at which the image is shown. We have adopted the observer point of view for Doppler shifts in which a negative v_LOS corresponds to a blueshift in the spectral line. The label L_em indicates the pixel with maximum emission in He I D₃, which we study in detail in Sect. 3.3. The black spectrum is an average over the entire field of view shown in the image. The emission feature in the observed He I D₃ spectrum at v_LOS ∼ 40 km s⁻¹ is an artifact resulting from a telluric correction applied to the spectra. Details of this procedure can be found in Libbrecht et al. (2017).