Radial motion of bursts #2 (left panel) and #3 (right panel) obtained from centroids. The colors correspond to different frequencies from 35 to 75 MHz. The velocities were calculated from the slopes of the fits and are given in the upper left corners. The vertical error bars in the two plots represent the extent of the FWHM of the beams, which varies with frequency. The horizontal error bars are due to averaging the data in time steps of 1 s.