The circular discharges in the center (for group (i)) provide information on the crosssection of the discharges through which the current flows. Figure shows a histogram of discharge sizes in this region. Representative images of selected discharges are included in the Figure , where the labels relate to those marking the vertical lines in the plot. The discharge diameter was determined from the average length of both ellipse axes. The distribution has a maximum at around 0.3 mm. Discharges located at around the maximum and below, with small diameters (< 0.4 mm), are mostly confined to the central area of the wire (spots A to C). Larger spots can have diameters larger than that of the wire (spot D). Discharge spots with a size significantly larger than the wire (about 0.8 mm, spot E) seem to consist of multiple overlapping spots that can not be separated with our evaluation and the resolution of the recorded images (see also Fig. ).