For midlatitude regions, routinely recorded ionograms have been used to investigate whether or not occurrence levels of (1) daytime first-hop distortions, (2) daytime second-hop spread, and (3) nighttime spread F are influenced by 10.7-cm solar-flux changes, because of associated upper atmosphere neutral-particle density (UA-NPD) changes. Recordings for a 5-year period (1979--1983) were used. It was found that generally speaking, occurrence levels of these parameters were lower for high solar-flux values and higher for low solar-flux values as variations occurred from day to dy. These are the results expected if the UA-NPD changes have an influence on the wave amplitudes of the medium-scale traveling ionospheric disturbances (MS-TIDs) thought to be responsible for the recording of these parameters. This association was particularly well defined for the occurrence of the daytime second-hop spread. It is suggested that non linear effects of the atmospheric gravity waves (AGWs) responsible for the MS-TIDs may be responsible for generating the daytime small-scale structures, which experimental results indicate are the ionospheric structures responsible for the second-hop spread. These structures may possibly be field aligned. ¿ American Geophysical Union 1996