Flux (panel a), P (panel b), and θ_r (panel c) of 2P observed on UT 2017 February 21 by HHO/HONIR as a function of wavelength. In panel a, we name the branches of discernible line emissions. The red line is a median-smoothed line of the original black points within the size of wavelength resolution. In panel b, the binned-average P is calculated within a rectangle region of 2.′′2 × 5.′′8. We mark the analyzed emission lines with the vertical lines in panels a and b. In panel c, the horizontal red line denotes the average θ_r of 0°.4.