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Ann. Geophys., 23, 2249-2257, 2005
www.ann-geophys.net/23/2249/2005/
© European Geosciences Union 2005
On the development and evolution of nonlinear ion acoustic wave packets
A. M. Hamza
Physics Dept., University of New Brunswick, POB 4400, Fredericton, E3B 5B-5A3, Canada
Abstract. A simple model of ion fluctuations (ion acoustic and ion cyclotron
fluctuations for example) driven by an electron current which leads to
intermittent fluctuations when the linear growth rate exceeds the wave packet
dispersion rate is analized. The normalized fluctuation amplitude
eφ0/T can be much larger than the mass ratio (me/mi) level
predicted by the conventional quasilinear theory or Manheimer's theory (see
references in this document), and where φ0 represents the amplitude
of the main peak of the ion fluctuations. Although the ion motion is linear,
intermittency is produced by the strong nonlinear electron response, which
causes the electron momentum input to the ion fluctuations to be spatially
localized. We treat the 1-D case because it is especially simple
from an intuitive and analytical point of view, but it is readily apparent
and one can put forward the conjecture that the effect occurs in a three
dimensional magnetized plasma. The 1-D analysis, as shown in this
manuscript will clearly help identify the subtle difference between
turbulence as conventionally understood and intermittency as it occurs in
space and laboratory plasmas.
Keywords. Meteorology and atmospheric dynamics (Turbulence)
– Ionosphere (Wave-particles interactions) – Space
plasma physics (Waves and instabilities)
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