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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 6
Ann. Geophys., 17, 712–722, 1999
https://doi.org/10.1007/s00585-999-0712-2
© European Geosciences Union 1999
Ann. Geophys., 17, 712–722, 1999
https://doi.org/10.1007/s00585-999-0712-2
© European Geosciences Union 1999

  30 Jun 1999

30 Jun 1999

A mode filter for plasma waves in the Hall-MHD approximation

C. Vocks1, U. Motschmann2, and K.-H. Glassmeier C. Vocks et al.
  • Institut für Geophysik und Meteorologie, Technische Universität Braunschweig, Mendelssohnstrasse 3, D-38106 Braunschweig, Germany
  • 1Now at Max-Planck-Institut für Aeronomie, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau, Germany
  • 2Also at the German Aerospace Center (DLR), Institute for Planetary Exploration, D-12484 Berlin, Germany

Abstract. A filter method is presented which allows a qualitative and quantitative identification of wave modes observed with plasma experiments on satellites. Hitherto existing mode filters are based on the MHD theory and thus they are restricted to low frequencies well below the ion cyclotron frequency. The present method is generalized to cover wave modes up to the characteristic ion frequencies. The spectral density matrix determined by the observations is decomposed using the eigenvectors of the linearized Hall-MHD equations. As the wave modes are dispersive in this formalism, a precise determination of the k->-vectors requires the use of multi-point measurements. Therefore the method is particularly relevant to multi-satellite missions. The method is tested using simulated plasma data. The Hall-MHD filter is able to identify the modes excited in the model plasma and to assign the correct energetic contributions. By comparison with the former method it is shown that the simple MHD filter leads to large errors if the frequency is not well below the ion cyclotron frequency. Further the range of validity of the linear theory is examined rising the simulated wave amplitudes.

Key words. Magnetospheric physics (MHD waves and instabilities; plasma waves and instabilities)

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