heating of the auroral ionosphere

Abstract. Numerical two-dimensional two-fluid MHD sim-ulations of dynamic magnetosphere-ionosphere (MI) cou-pling have been performed to model the effects imposed on the auroral ionosphere by a powerful HF radio wave trans-mitter. The simulations demonstrate that modifications of the ionospheric plasma temperature and recombination due to artificial heating may trigger the ionospheric feedback in-stability when the coupled MI system is close to the state of marginal stability. The linear dispersion analysis of MI coupling has been performed to find the favorable conditions for marginal stability of the system. The development of the ionospheric feedback instability leads to the generation of shear Alfvén waves which resonate in the magnetosphere between the heated ionospheric E-region and the strong gra-dient in the Alfvén speed at altitudes of 1–2RE. The appli-cation of the numerical results for the explanation of obser-vations performed by low-orbiting satellites above the high-latitude ionosphere heated with a high power ground-based HF transmitter is discussed. Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions; MHD waves and in-stabilities)