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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 3
Ann. Geophys., 27, 1321–1330, 2009
https://doi.org/10.5194/angeo-27-1321-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 1321–1330, 2009
https://doi.org/10.5194/angeo-27-1321-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  18 Mar 2009

18 Mar 2009

Pre-storm NmF2 enhancements at middle latitudes: delusion or reality?

A. V. Mikhailov1 and L. Perrone2 A. V. Mikhailov and L. Perrone
  • 1Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142190, Russia
  • 2Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome 00143, Italy

Abstract. A critical analysis of recent publications devoted to the NmF2 pre-storm enhancements is performed. There are no convincing arguments that the observed cases of NmF2 enhancements at middle and sub-auroral latitudes bear a relation to the following magnetic storms. In all cases considered the NmF2 pre-storm enhancements were due to previous geomagnetic storms, moderate auroral activity or they presented the class of positive quiet time events (Q-disturbances). Therefore, it is possible to conclude that there is no such an effect as the pre-storm NmF2 enhancement as a phenomenon inalienably related to the following magnetic storm. The observed nighttime NmF2 enhancements at sub-auroral latitudes may result from plasma transfer from the plasma ring area by meridional thermospheric wind. Enhanced plasmaspheric fluxes into the nighttime F2-region resulted from westward substorm-associated electric fields is another possible source of nighttime NmF2 enhancements. Daytime positive Q-disturbances occurring under very low geomagnetic activity level may be related to the dayside cusp activity.

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