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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 24, issue 11
Ann. Geophys., 24, 2959–2979, 2006
https://doi.org/10.5194/angeo-24-2959-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 2959–2979, 2006
https://doi.org/10.5194/angeo-24-2959-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  21 Nov 2006

21 Nov 2006

Low-frequency electrostatic waves in the ionospheric E-region: a comparison of rocket observations and numerical simulations

L. Dyrud1,2, B. Krane3, M. Oppenheim4, H. L. Pécseli2,5, K. Schlegel6, J. Trulsen2,7, and A. W. Wernik2,8 L. Dyrud et al.
  • 1Center for Remote Sensing, 3702 Pender Dr., Fairfax, VA 22030, USA
  • 2Centre for Advanced Study, Drammensveien 78, N-0271 Oslo, Norway
  • 3Norwegian Defense Research Establishment (NDRE), Box 25, N-2027 Kjeller, Norway
  • 4Center for Space Physics, Boston University, 725 Commonwealth Ave., Boston MA 02215, USA
  • 5University of Oslo, Physics Department, P.O. Boks 1048 Blindern, N-0316 Oslo, Norway
  • 6Max Planck Institute für Sonnensystemforschung, D-37191 Katlenburg-Lindau, Germany
  • 7University of Oslo, Institute of Theoretical Astrophysics, P.O. Boks 1029 Blindern, N-0315 Oslo, Norway
  • 8Space Research Center, Polish Academy of Sciences, ul. Bartycka 18a, 00-716 Warsaw, Poland

Abstract. Low frequency electrostatic waves in the lower parts of the ionosphere are studied by a comparison of observations by instrumented rockets and of results from numerical simulations. Particular attention is given to the spectral properties of the waves. On the basis of a good agreement between the observations and the simulations, it can be argued that the most important nonlinear dynamics can be accounted for in a 2-D numerical model, referring to a plane perpendicular to a locally homogeneous magnetic field. It does not seem necessary to take into account turbulent fluctuations or motions in the neutral gas component. The numerical simulations explain the observed strongly intermittent nature of the fluctuations: secondary instabilities develop on the large scale gradients of the largest amplitude waves, and the small scale dynamics is strongly influenced by these secondary instabilities. We compare potential variations obtained at a single position in the numerical simulations with two point potential-difference signals, where the latter is the adequate representation for the data obtained by instrumented rockets. We can demonstrate a significant reduction in the amount of information concerning the plasma turbulence when the latter signal is used for analysis. In particular we show that the bicoherence estimate is strongly affected. The conclusions have implications for studies of low frequency ionospheric fluctuations in the E and F regions by instrumented rockets, and also for other methods relying on difference measurements, using two probes with large separation. The analysis also resolves a long standing controversy concerning the supersonic phase velocities of these cross-field instabilities being observed in laboratory experiments.

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