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Annales Geophysicae


Time-dependent, three-dimensional numerical simulations of the reduced MHD model describing shear Alfve ́n waves in the magnetosphere provide an interesting prediction superficially similar to results of several iono- spheric heating experiments conducted at high altitudes. In these experiments, heating of the ionospheric F-region with a constant/zero-frequency beam of HF waves causes luminous structures in the ionosphere in the form of a ring or a solid spot with a characteristic size comparable to the size of the heated spot. Simulations suggest that spots/rings or similar optical appearance might be associated with a magnetic field- aligned current system produced by the ionospheric heat- ing. Two of the most interesting features of this current system are (1) strong localization across the ambient mag- netic field and (2) distinctive non-symmetrical luminous sig- natures (ring/spot) in magnetically conjugate locations in the ionosphere.