PowerPoint Presentation Standing wave mode structure

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Modeling Geospace Plasma Mass Density Based on
the Frequency of ULF Waves
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• Standing Alfvén waves are routinely observed by
  spacecraft. The waves often consist of multiple
  harmonics as demonstrated by the example from the
  CRRES spacecraft shown on the left. The
  perigee-to-perigee dynamic spectra of the
  electric (second panel) and magnetic (third
  panel) fields show a band structure of the
  fundamental to third harmonics. Since the
  frequency of the harmonics is related to the
  plasma mass density, it is possible to estimate
  the density from the observed harmonics. The
  plasma mass density (top panel), obtained by the
  plasma wave instrument, does not provide direct
  information on the mass density.
• The spacing of the harmonic frequency is related
  to the mass density variation along the magnetic
  field. Observed spacing in turn can be used to
  determine the density variation. Histograms of
  the spacing obtained from the CRRES data,
  normalized to the fundamental frequency, are on
  the right for the the high density and low
  density regions. The spacing is in the range 1.5
  to 1.7, which implies that the mass density
  decreases approximately as 1/R, where R
  geocentric distance along a field line.
• This proves that standing Alfvén waves are a
  powerful tool in specifying the density in the
  magnetosphere.