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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, 745–751, 2005
https://doi.org/10.5194/angeo-23-745-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 745–751, 2005
https://doi.org/10.5194/angeo-23-745-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Mar 2005

30 Mar 2005

The effects of the pre-reversal ExB drift, the EIA asymmetry, and magnetic activity on the equatorial spread F during solar maximum

C.-C. Lee1, J.-Y. Liu2, B. W. Reinisch3, W.-S. Chen2, and F.-D. Chu2,4 C.-C. Lee et al.
  • 1General Education Center, Ching-Yun University, No. 229, Chienshin Road, Jhongli City, Taoyuan County 320, Taiwan
  • 2Institute of Space Science, National Central University, No. 300, Jhongda Rd., Jhongli City, Taoyuan County 320, Taiwan
  • 3Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk Street, Lowell, MA 01854, USA0, Taiwan
  • 4National Standard Time and Frequency Laboratory, Telecommunication Laboratories, No. 12 Lane 551 Ming-Tsu Road Sec. 5, Yang-Mei 326, Taiwan

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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