Spectra averaged over the region enclosed by a rectangle in green displayed in Fig. 7, centered around Si IV 1393.76 Å. The spectra are displayed for six times around the apparent starting time of E₇ at 04:50 UT. We apply a fitting with a single Gaussian to the spectrum at 04:48:58 UT called single component (SC); and a fitting with two Gaussian functions to the other spectra, called the red (RC) and the blue component (BC). The resulting velocity and uncertainty is written for each component in the legends. The vertical dashed lines indicate the locations in Doppler velocities of the peaks for the two components. The indicated times are the central times of the IRIS fast rasters. The χ_r² value resulting from each fit is indicated next to the time in UT for each spectrum.