Stokes parameters Q (central panel) and U (lower panel) on day +76. For presentation, the data were binned to 65 Å (25 px). The two horizontal segments mark the weighted average values within the wavelength range (4500–7500 Å). The dashed curves trace a Serkowski-Whittet law with P_max = 0.15%, θ = 169.7 degrees, and λ_max = 4500 Å. The upper panel presents the signal-to-noise ratio per resolution element in the intensity spectrum.