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Excitation and steepening of ion‐acoustic waves in the ionospheric Alfvén resonator

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  • A nonlinear two-dimensional fluid model describing excitation of the ionospheric Alfven resonator by a shear Alfven wave coming from the magnetosphere is developed. Initially, the plasma is in an equilibrium defined by a balance between the gravity, electric field, and pressure gradient forces. This equilibrium is perturbed when a standing Alfven wave is excited in the resonator. The nonlinear Lorentz force of the wave creates converging and diverging plasma flows along the geomagnetic field, thus producing compressions and rarefactions in the plasma density. Simulation reveals that density perturbations evolve into ion-acoustic shock waves in a process similar to the nonlinear steepening of sound waves in neutral gases. A shock associated with compression of hydrogen ions propagates faster than a shock associated with compression of oxygen ions. One-dimensional shock-capturing Poisson simulation reveals that the shocks appear as double layers at first, but then they decay into ion-acoustic wave packets. The drop of potential across each shock is negligible at any stage of shock's development, making these shocks unfavorable for auroral electron acceleration.

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    Article (Published)
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    © 2010 American Geophysical Union. This version of this article is open access and can be downloaded and shared. The original author(s) and source must be cited.
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    • Sydorenko, Dmytro, Rankin, Robert, & Kabin, Konstantin. (2010). Excitation and steepening of ion‐acoustic waves in the ionospheric Alfvén resonator. Journal of Geophysical Research: Space Physics, 115(A11), 1-12.
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