Emergence and convergence of pores A and B in GST TiO and HMI intensity images. The blue dashed lines are reference lines to show the convergence of pores. The time-distance plot (panel d) of HMI intensity images along the yellow dashed line (S1 in (f)). The yellow and green dotted lines are used to derive the attached convergence speeds, and the red dotted and dashed lines represent the start of convergence of Pore B and the eruption onset, respectively.