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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 7
Ann. Geophys., 15, 899–907, 1997
https://doi.org/10.1007/s00585-997-0899-z
© European Geosciences Union 1997
Ann. Geophys., 15, 899–907, 1997
https://doi.org/10.1007/s00585-997-0899-z
© European Geosciences Union 1997

  31 Jul 1997

31 Jul 1997

Evidence and effects of a wave-driven nonlinear current in the equatorial electrojet

M. Oppenheim M. Oppenheim
  • Max-Planck-Institut für Aeronomie, Postfach 20, D-37191 Katlenburg-Lindau, Germany

Abstract. Ionospheric two-stream waves and gradient-drift waves nonlinearly drive a large-scale (D.C.) current in the E-region ionosphere. This current flows parallel to, and with a comparable magnitude to, the fundamental Pedersen current. Evidence for the existence and magnitude of wave-driven currents derives from a theoretical understanding of E-region waves, supported by a series of nonlinear 2D simulations of two-stream waves and by data collected by rocket instruments in the equatorial electrojet. Wave-driven currents will modify the large-scale dynamics of the equatorial electrojet during highly active periods. A simple model shows how a wave-driven current appreciably reduces the horizontally flowing electron current of the electrojet. This reduction may account for the observation that type-I radar echoes almost always have a Doppler velocity close to the acoustic speed, and also for the rocket observation that electrojet regions containing gradient-drift waves do not appear also to contain horizontally propagating two-stream waves. Additionally, a simple model of a gradient-drift instability shows that wave-driven currents can cause nonsinusoidal electric fields similar to those measured in situ.

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