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Ann. Geophys., 25, 483-493, 2007
www.ann-geophys.net/25/483/2007/
© European Geosciences Union 2007
Synchronous NmF2 and NmE daytime variations as a key to the mechanism of quiet-time F2-layer disturbances
A. V. Mikhailov, V. H. Depuev, and A. H. Depueva
Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142190, Russia
Abstract. The observed NmF2 and NmE variations were analyzed for the periods of
positive and negative quiet-time F2-layer disturbances (Q-disturbances)
observed in the midlatitude daytime F2-layer to specify the mechanism of
their origin. The noontime δNmF2 and δNmE deviations
demonstrate a synchronous type of variation which can be explained by
vertical gas motion in the thermosphere. This neutral gas motion should
result in atomic abundance variations, the latter being confirmed by the
Millstone Hill ISR observations for periods of positive and negative
Q-disturbance events. The analysis of the ISR data has shown that atomic
oxygen concentration variations are the main cause of the daytime F2-layer
Q-disturbances. The auroral heating which controls the poleward thermospheric
wind is considered to be the basic mechanism for the Q-disturbances, however,
the specific mechanisms of positive and negative Q-disturbances are
different. Some morphological features of the Q-disturbances revealed
earlier are explained in the scope of the proposed concept.
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