The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors

The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors

E. Yizengaw1, M. B. Moldwin2, E. Zesta3, C. M. Biouele4, B. Damtie5, A. Mebrahtu6, B. Rabiu7, C. F. Valladares1, and R. Stoneback8

1Institute for Scientific Research, Boston College, Boston, Massachusetts, USA, 2Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA, 3NASA Goddard Space Flight Center, Greenbelt, Maryland, USA, 4Department of Physics, University of Yaoundé I, Yaoundé, Cameroon, 5Washera Geospace and Radar Science Laboratory, Bahir Dar University, Bahir Dar, Ethiopia, 6Department of Physics, Adigrat University, Adigrat, Ethiopia, 7National Space Research and Development Agency, Abuja, Nigeria, 8Center for Space Sciences, University of Texas at Dallas, Richardson, Texas, USA

Ann. Geophys., 32, 231–238, 2014 www.ann-geophys.net/32/231/2014/ doi:10.5194/angeo-32-231-2014

Correspondence to:

E. Yizengaw ,
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Key Points:

• Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities)

Abstract:

While the formation of equatorial electrojet (EEJ) and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM) instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study’s results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh–Taylor (RT) instability growth rate, is stronger in the American sector and weaker in the African sector – why are the occurrence and amplitude of equatorial irregularities stronger in the African sector? 

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