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Ann. Geophys., 25, 1531-1541, 2007
www.ann-geophys.net/25/1531/2007/
© European Geosciences Union 2007
Daytime F2-layer negative storm effect: what is the difference between storm-induced and Q-disturbance events?
A. V. Mikhailov, A. H. Depueva, and V. H. Depuev
Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142190, Russia
Abstract. Negative F2-layer storms related to geomagnetic activity and quiet-time disturbances (Q-disturbances)
belong to different classes of events and
exhibit different morphology. Mid-latitude daytime Q-disturbances, unlike
the usual negative F2-layer storms, demonstrate NmF2 and hmF2 in-phase
variations. An analysis of Millstone Hill ISR observations for usual and
Q-disturbances has shown the difference in the controlling aeronomic
parameter variations for the two classes of events. The decrease in atomic
oxygen concentration provides the main contribution to the hmF2 decrease
below the monthly median level during Q-disturbance events. Unlike the usual
negative storms, the negative effect takes place in the whole topside
ionosphere under Q-disturbance conditions. The difference is due to
different effective plasma scale heights in the two cases. Clustering of
the usual negative F2-layer disturbances around equinoxes and Q-disturbances
around winter solstice, as well as different latitudinal variations for the
occurrence of the two types of disturbances is due to their different
formation mechanisms.
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