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tokens: the pre-event frame acquired at 16:04 UT from the LASCO-C2 frame containing the CME at 19:30 UT. LASCO images were also used to measure the plane-of-the-sky (POS) velocity of the prominence, ν POS ≃ 300 km s −1 , as well as its projected thickness, D ≃ 56 000 km, which was taken as an approximation of the prominence average LOS thickness, under the simple assumption of cylindrical geometry. Fig. 1. LASCO-C2 mass image acquired at 19:30 UT on August 2, 2000, and intensity distribution of the Ly α line along the UVCS slit (measured at the same time and represented with color gradient). The two points considered in this analysis (P1, located at a helio-latitude of ~57° N, and P2, located at ~37° N) are also indicated. UVCS recorded spectra of several UV coronal lines (see Table 1 of Paper I for a complete list) as the prominence crossed its field of view (FOV), a 40 arcmin long slit placed perpendicularly to the solar radius at a latitude of 40°NE and heliocentric distance of 2.3 R ⊙ (see Fig. 1 ). In particular, spectral profiles of the neutral hydrogen Lyman- α ( λ 12 = 1215.67 Å) and Lyman- β ( λ 13 = 1025.72 Å) lines were acquired with a spatial resolution of 21 arcsec (≈15 000 km) and an integration time of 120 s during the entire CME event. Both lines systematically appear to be the superposition of two components with different widths, the narrower one representing, in our interpretation, real prominence emission, while the broader one is more likely due to plasma in the PCTR or, alternatively, in the hot plasma shroud surrounding the prominence (see Habbal et al. 2010 ). Table 1. Observed quantities and modeling results. The two components were separated with a double Gaussian fit to the line profiles, and consistency of the fit was verified with a minimum chi-squared analysis (see Paper I). A mean pre-event spectrum, obtained by averaging over several exposures preceding the onset of the eruption, was subtracted from the line profiles in order to remove the contribution from the quiet corona surrounding the prominence from the observed emission. This correction may not be accurate because, as evidenced by the depleted (black) region around the prominence in Fig. 1 , much of the pre-event corona has been blown away by the CME during the eruption. However, prominences are generally very bright in the Lyman lines (e.g., Ciaravella et al. 2003 ), and the quiet-corona contribution can be assumed to be very small; therefore possible uncertainties related to the background subtraction can be considered negligible in this case. Figure 2 reports the total integrated intensities of the Ly α and Ly β narrow components as functions of time and position along the UVCS slit. The prominence exhibits a complex structure in both lines, with ramifications and apparently superimposed emission features. The intensity of the Ly α line is up to 250 times higher than that of the Ly β . The Ly α to Ly β intensity ratio is consistent with the value somewhat