Large scale waves in the thermosphere observed by the AE-C satellite

Atmospheric Explorer C (AE-C) data are analyzed to study wavelike perturbations in the thermosphere at an altitude of about 260 km. Four geophysical parameters are analyzed. These are nitrogen and oxygen densities, electron density and ion temperature as measured by three different instruments on board AE-C. The data are processed by normalizing them to their average values and their fluctuations are obtained by passing the normalized data through a high pass filter. These fluctuations exhibit strong periodicities that persist throughout the records, regardless of the filter cutoff frequency. The fluctuations are cross correlated by direct comparison, by comparison of their spectral content as obtained by the MEM and FFT, and by computing cross correlation functions.