Illustration of the process of bandpass-filtering the BP region. The leftmost panel shows the AIA 193 Å image at the beginning of the time range of interest. The remaining three panels show images at three times separated by 4 min. At each pixel, the time series has been bandpass-filtered around the period of 8 min with a Hann filter with a typical width equal to the mode frequency. The temporal evolution of the bandpass-filtered images is available as an online movie.