IONOSPHERIC DRIFT SIMILARITIES AT MAGNETIC CONJUGATE AND NONCONJUGATELOCATIONS

Suggestions in the literature indicate that the observed similarity in ionospheric drifts between Arecibo-summer and Shigaraki-winter and ag ain between Arecibo-winter and Shigaraki-summer are due to conjugate e ffects owing to the circumstance that the Shigaraki magnetic conjugate point has the same latitude as does Arecibo (in the opposite hemisphe re). Here we develop this theory further from one of association to on e of cause and effect. We base our explanation on the control of drift s at conjugate locations resting with the location of higher electrica l conductance and suggest that this usually results in practice in sum mer hemisphere control of the winter hemisphere at night, with the day time case being more complicated, Consequences of our theory are that the Arecibo-summer Shigaraki-winter similarity is, indeed, due to conj ugate effects but that the Arecibo-winter Shigaraki-summer similarity has little to do with conjugacy. We combine empirical models of thermo sphere and ionosphere structure and dynamics to test our conceptual id eas. We make predictions for such reverse-season similarities for othe r pairs of incoherent scatter radar locations.