Nonlinear dynamics of inertial Alfvén waves in the upper ionosphere: Parametric generation of electrostatic convective cells

We consider the excitation of convective cells in the parametric decay of finite amplitude (inertial) Alfvén waves. We formulate a set of coupled equations describing the nonlinear interaction of Alfvén waves and the electrostatic convective mode and obtain the nonlinear dispersion relation for elec...

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Bibliographic Details
Published in:Journal of Geophysical Research - Space Physics 2003-07, Vol.108 (A7), p.1291-n/a
Main Authors: Pokhotelov, Oleg A., Onishchenko, Oleg G., Sagdeev, Roald Z., Treumann, Rudolf A.
Format: Article
Language:English
Subjects:
auroral potentials
auroral resonator
electrostatic convective cells
inertial Alfvén waves
Magnetosphere/ionosphere interactions
Magnetospheric Physics
Plasma convection
shear flow generation
Space Plasma Physics
Turbulence
Wave/wave interactions
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Summary:We consider the excitation of convective cells in the parametric decay of finite amplitude (inertial) Alfvén waves. We formulate a set of coupled equations describing the nonlinear interaction of Alfvén waves and the electrostatic convective mode and obtain the nonlinear dispersion relation for electrostatic convection cells. Generation of convection cells takes place only when dispersive effects due to the electron skin depth come into play. The generation of such cells is due to the Reynolds stresses of short‐scale Alfvén waves. These are nonzero when the perpendicular Alfvén wavelengths are of the order of the collisionless electron skin depth. The convective cells are nonoscillatory two‐dimensional modes with wave vector perpendicular to that of the pump Alfvén wave. The nonlinear growth rate of these cells is a sensitive function (proportional to k5) of the wave number k of the Alfvénic pump wave. This implies that the instability transfers wave energy from the short wavelength regime of the inertial Alfvén wave to the long wavelength regime of the convective cells which is typical for an inverse turbulent cascade. We also discuss the relation of the new parametric regime to the parametric wave‐wave interaction of two counterstreaming inertial Alfvén waves. Application to satellite observations of inertial Alfvén waves in the auroral ionosphere shows agreement of the scales and explains the observed large amplitudes of the waves. It is shown that convective cells produced by the parametric instability could cause the fine structure of the turbulent Alfvén boundary layer and can play an important role in the ionospheric plasma turbulence as well as the energy source for auroral structures.
ISSN:0148-0227
2156-2202
DOI:10.1029/2003JA009888