Precipitation and nonlinear effects in geomagnetic field line resonances

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Abstract

The structure of auroral arcs sustained by field line resonances (FLRs) is determined using a model that describes the interplay between ionospheric feedback, nonlinear, and dispersive effects in a curvilinear geomagnetic topology. The model includes modulation of Pedersen conductance by hundreds of eV electrons that precipitate in the ionosphere through the action of shear Alfvén wave field-aligned currents (FACs). The competition between ionospheric feedback dissipation, wave dispersion, and nonlinearity results in large-amplitude, long-period oscillations of the FAC, and in emission of slow-moving small-scale secondary auroral arcs and density perturbations. Using observed values of nightside conductivities and realistic topology of geomagnetic field lines, we obtain FLRs with frequencies in the range of a few mHz, spatial scales up to several km near the ionosphere, and FAC amplitudes extending to tens of μA/m2. Our model explains the excitation of structured auroral arcs in regions of low ionospheric conductance. Copyright 2003 by the American Geophysical Union.

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Prakash, M., Rankin, R., & Tikhonchuk, V. T. (2003). Precipitation and nonlinear effects in geomagnetic field line resonances. Journal of Geophysical Research: Space Physics, 108(A4). https://doi.org/10.1029/2002JA009383

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