Expected fraction of cold electron gas as a function of radial distance and neutral density – contour plots for 20% (marine), 40% (blue), 60% (green), 80% (orange), and 100% (brown). The black dotted lines show 1 /r² neutral density profiles for the COPS values observed at the points marked with stars on the dates shown. The fraction of cold electrons in the sweep fits in Table 1 is indicated in parenthesis.