Comparisons of observed and simulated (a) solar wind speed and (b) particle number density at Earth for 19–28 June 2015. The time period shown includes the signatures of all five simulated CMEs. Four sets of simulated results are shown. The first two sets of predicted results were obtained with identical parameters for the background solar wind as those used for the results shown in Figure 18 except that, in one case, the standard GONG map (S-Map) was used and, in the other case, the zero-point corrected GONG map (ZPC-Map) was used. The third and fourth set of results were again obtained identical parameters and the same two synoptic maps, but with a modified expression for the plasma density (S-Map MD and ZPC-Map MD).