(a) Base-difference image of the slit in STEREO-A/EUVI at 304 ﹩\mathring{{\rm{A}}}﹩. Separation of the two ribbons is indicated by the dashed red lines. The vertical dashed line marks the first appearance time of the two ribbons. (b) Height–time measurement of the CME front (black) and core (red), associated with the results from a linear fit (solid line) and a quadratic fit (dashed line). (c) Speed–time measurement. The dashed lines indicate the speed obtained from the quadratic fit in panel (b). (d) Height–speed measurement. The vertical black line indicates the height of the front at 6.5 R _⊙, and the red one indicates the height of the core at the same time. The solid lines are the linear-fit results.