ACCURACY OF O-O COLLISION CROSS-SECTION DEDUCED FROM IONOSPHERE-THERMOSPHERE OBSERVATIONS()

Aeronomic observations applied to the empirical derivation of the ion- neutral collision cross-section-a basic parameter governing the mutual interactions between the neutral and plasma components in the Earth's upper atmosphere-have given values considerably larger than those der ived from theory. The empirical scheme uses the plasma velocities obta ined with the Incoherent Scatter Radar and the neutral winds obtained with the Fabry-Perot Interferometer. It is shown here that such an ana lysis overestimates the collision cross-section due to the effects of errors in the observables. The effect may be sufficiently large to bri ng about agreement with theory, and calls for a re-analysis of the aer onomic data using methods which minimize the bias caused by measuremen t errors.