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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 5
Ann. Geophys., 27, 2053-2056, 2009
https://doi.org/10.5194/angeo-27-2053-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: 12th International Symposium on Equatorial Aeronomy...

Ann. Geophys., 27, 2053-2056, 2009
https://doi.org/10.5194/angeo-27-2053-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  05 May 2009

05 May 2009

On the origin of pre-reversal enhancement of the zonal equatorial electric field

M. C. Kelley1, R. R. Ilma1, and G. Crowley2 M. C. Kelley et al.
  • 1School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA
  • 2Atmospheric & Space Technology Research Associates (ASTRA), San Antonio, TX, USA

Abstract. In November 2004, a large and variable interplanetary electric field (IEF) was felt in the reference frame of the Earth. This electric field penetrated to the magnetic equator and, when the Jicamarca Radio Observatory (JRO) was in the dusk sector, resulted in a reversal of the normal zonal component of the field. In turn, this caused a counter-electrojet (CEJ), a westward current rather than the usual eastward current. At the time of the normal pre-reversal enhancement (PRE) of the eastward field, the Jicamarca incoherent scatter radar (ISR) observed that the westward component became even more westward. Two of the three current explanations for the PRE depend on the neutral wind patterns. However, this unique event was such that the neutral wind-driven dynamos could not have changed. The implication is that the Haerendel-Eccles mechanism, which involves partial closure of the equatorial electrojet (EEJ) after sunset, must be the dominant mechanism for the PRE.

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