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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 10
Ann. Geophys., 15, 1309–1315, 1997
© European Geosciences Union 1997
Ann. Geophys., 15, 1309–1315, 1997
© European Geosciences Union 1997

  31 Oct 1997

31 Oct 1997

Midday reversal of equatorial ionospheric electric field

R. G. Rastogi R. G. Rastogi
  • INSA Senior Scientist, Department of Physics and Space Sciences, Gujarat University, Ahmedabad 380 009, India

Abstract. A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

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