All available, computer-readable, thermal ion composition measurements from Earth-orbiting satellites have been put into a common computer file format for easy manipulation. The ion measurements obtained under solar maximum conditions at polar cap latitudes within a 6-hour magnetic local time window about noon in the summer were culled from this data set for comparison to similar data for a solar minimum period. The observations show distinctive solar cycle variations in topside F region altitudes distributions of O+ and H+ concentrations that reflect changes in the polar wind source region. The summer noontime polar cap data are statistically the best ordered of all seasons and magnetic local time ranges in the polar cap because of the domination of solar EUV effects over those of auroral energy inputs and convection processes. The polar cap minor ion, H+, is in charge exchange equilibrium to higher altitude during solar maximum than solar minimum periods, reflecting the change in altitude where the light ion polar wind development begins. The concentration of the major ion, O+, increases from solar minimum to solar maximum due to changes in photoionization rates and heating of the plasma and neutral thermosphere. The data support the strong dependence of the polar ionosphere and polar wind features on the F10.7 index and are consistent with the results of the model study of the same region and similar extremes of solar activity by Cannata and Gombosi. ¿American Geophysical Union 1990