A mode filter for plasma waves in the Hall-MHD approximation
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....
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1999-06-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/17/712/1999/angeo-17-712-1999.pdf |
| Summary: | 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 <i>k-></i>-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.<br><br><b>Key words.</b> Magnetospheric physics (MHD waves and
instabilities; plasma waves and instabilities) |
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| ISSN: | 0992-7689 1432-0576 |