Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.490 IF 1.490
  • IF 5-year value: 1.445 IF 5-year
    1.445
  • CiteScore value: 2.9 CiteScore
    2.9
  • SNIP value: 0.789 SNIP 0.789
  • IPP value: 1.48 IPP 1.48
  • SJR value: 0.74 SJR 0.74
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 88 Scimago H
    index 88
  • h5-index value: 21 h5-index 21
Volume 23, issue 7
Ann. Geophys., 23, 2679–2686, 2005
https://doi.org/10.5194/angeo-23-2679-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 2679–2686, 2005
https://doi.org/10.5194/angeo-23-2679-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  14 Oct 2005

14 Oct 2005

Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study

P. T. I. Eriksson1, L. G. Blomberg1, A. D. M. Walker2, and K.-H. Glassmeier3 P. T. I. Eriksson et al.
  • 1Alfvén Laboratory, Royal Institute of Technology, Stockholm, Sweden
  • 2School of Pure and Applied Physics, University of KwaZulu-Natal, Durban, South Africa
  • 3Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Braunschweig, Germany

Abstract. Three ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the events by means of the phase shift and the azimuthal separation between the satellites. Also, the polarisation of the electric and magnetic fields is examined in a field-aligned coordinate system, which, in turn, gives the mode of the oscillations. The large-inclination orbits of Cluster allow us to examine the phase relationship between the electric and magnetic fields along the field lines. The events studied have large azimuthal wave numbers (m~100), two of them have eastward propagation and all are in the poloidal mode, consistent with the large wave numbers. We also use particle data from geosynchronous satellites to look for signatures of proton injections, but none of the events show any sign of enhanced proton flux. Thus, the drift-bounce resonance instability seems unlikely to have played any part in the excitation of these pulsations. As for the drift-mirror instability we conclude that it would require an unreasonably high plasma pressure for the instability criterion to be satisfied.

Keywords. Ionosphere (Wave propagation) – Magnetospheric physics (Plasma waves and instabilities; Instruments and techniques)

Publications Copernicus
Download
Citation