Daytime F2-layer negative storm effect: what is the difference between storm-induced and Q-disturbance events?

摘要

Negative F2-layer storms related to geomagnetic activity and quiet-time disturbances (Q-disturbances) belong to different classes of events andexhibit different morphology. Mid-latitude daytime Q-disturbances, unlikethe usual negative F2-layer storms, demonstrate NmF2 and hmF2 in-phasevariations. An analysis of Millstone Hill ISR observations for usual andQ-disturbances has shown the difference in the controlling aeronomicparameter variations for the two classes of events. The decrease in atomicoxygen concentration provides the main contribution to the hmF2 decreasebelow the monthly median level during Q-disturbance events. Unlike the usualnegative storms, the negative effect takes place in the whole topsideionosphere under Q-disturbance conditions. The difference is due todifferent effective plasma scale heights in the two cases. Clustering ofthe usual negative F2-layer disturbances around equinoxes and Q-disturbancesaround winter solstice, as well as different latitudinal variations for theoccurrence of the two types of disturbances is due to their differentformation mechanisms.