In situ measurements of neutral and electron density wave structure from the Explorer 32 satellite

In situ measurements of neutral particle and electron density from the Explorer 32 satellite have provided direct evidence that gravity waves in the thermosphere are associated with wave-like structure in the F region electron density. The ionospheric wave structure amplitude and spatial extent are consistent with those characteristics for travelling ionospheric disturbances (TID). Although the observed neutral and electron density wave structures are often out of phase, in some cases there was no correlation between the waves. Because of the lack of observation of all of the required ionospheric and neutral wave characteristics, it is not possible to quantitatively interpret the observed phase relationships. However, the observed amplitudes of the wave structure (±10 to ±30% in electron and neutral density) are consistent with theoretical expectations. In the one case where the electron temperature structure could be studied, the electron temperature was out of phase with the electron density. The phase relationship between the electron density and temperature wave structure probably results from local cooling effects in the ionospheric plasma.