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Ann. Geophys., 26, 1605-1615, 2008
www.ann-geophys.net/26/1605/2008/
© European Geosciences Union 2008
On the dispersion law of low-frequency electron whistler waves in a multi-ion plasma
B. V. Lundin1 and C. Krafft2
1Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Sciences, Troitsk, Moscow Region, 142190, Russia
2Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, 91128 Palaiseau Cedex, France
Abstract. A new and simple dispersion law for extra-low-frequency electron whistler
waves in a multi-ion plasma is derived. It is valid in a plasma with finite
ratio ωc/ωpe of electron gyro-to-plasma frequency and
is suitable for wave frequencies much less than ωpe but well
above the gyrofrequencies of most heavy ions. The resultant contribution
of the ions to the dispersion law is expressed by means of the lower hybrid
resonance frequency, the highest ion cutoff frequency and the relative
content of the lightest ion. In a frequency domain well above the ions'
gyrofrequencies, this new dispersion law merges with the "modified electron whistler dispersion law" determined in
previous works by the authors. It is shown that it fits well to the total
cold plasma electron whistler dispersion law, for different orientations of
the wave vectors and different ion constituents, including negative ions or
negatively charged dust grains.
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