Evolution of the first large plume. a1–a5: SDO/AIA 171 Å observations. The blue arrow in panel a2 points to the brightening in the bubble. White dashed line in panel a3 marks the position of time–distance diagrams in Figs. 4a–d. The white curve in panel a5 depicts the variation of normalized intensity of SDO/AIA 171 Å along the white line in panel a5. b1–b5: NVST Hα center observations. The black line in panel b3 marks the slit position of time–distance diagram in Fig. 4e. The blue curve in panel b5 depicts the variation of normalized intensity of the inverse Hα center along the blue line in panel b5. c1–c5: NVST Hα blue wing (−0.4 Å) observations. d1–d5: corresponding Doppler signals. The contours in panels c1–c5 and d1–d5: outline the corresponding inverse Hα center with a level of 0.25 of the normal intensity. The black horizontal arrows mark the slender void thread in panels a4, a5 and b4, b5.