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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 3
Ann. Geophys., 23, 753–757, 2005
https://doi.org/10.5194/angeo-23-753-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 753–757, 2005
https://doi.org/10.5194/angeo-23-753-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Mar 2005

30 Mar 2005

Simultaneous observations of the main trough using GPS imaging and the EISCAT radar

R. W. Meggs1, C. N. Mitchell1, and V. S. C. Howells2 R. W. Meggs et al.
  • 1Department of Electronic and Electrical Engineering, University of Bath, BA2 7AY Bath, UK
  • 2Rutherford-Appleton Laboratory, Chilton, OX11 0QX, UK

Abstract. We use a digisonde at Jicamarca and a chain of GPS receivers on the west side of South America to investigate the effects of the pre-reversal enhancement (PRE) in ExB drift, the asymmetry (Ia) of equatorial ionization anomaly (EIA), and the magnetic activity (Kp) on the generation of equatorial spread F (ESF). Results show that the ESF appears frequently in summer (November, December, January, and February) and equinoctial (March, April, September, and October) months, but rarely in winter (May, June, July, and August) months. The seasonal variation in the ESF is associated with those in the PRE ExB drift and Ia. The larger ExB drift (>20m/s) and smaller |Ia| (<0.3) in summer and equinoctial months provide a preferable condition to development the ESF. Conversely, the smaller ExB drift and larger |Ia| are responsible for the lower ESF occurrence in winter months. Regarding the effects of magnetic activity, the ESF occurrence decreases with increasing Kp in the equinoctial and winter months, but not in the summer months. Furthermore, the larger and smaller ExB drifts are presented under the quiet (Kp<3) and disturbed (Kp≥3) conditions, respectively. These results indicate that the suppression in ESF and the decrease in ExB drifts are mainly caused by the decrease in the eastward electric field.

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