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Experimental results from three ionospheric HF pumpingexperiments in overdense E or F regions are summarized. The experiments wereconducted by the use of the EISCAT HF Heating facility located nearTroms\uf8, Norway, allowing HF pumping the ionosphere in a near geomagneticfield-aligned direction. Distinctive features related to auroral activationsin the course of the experiments are identified. Typical features observed inall experiments are the following: generation of scattered components indynamic HF radio scatter Doppler spectra; strong increase of iontemperatures Ti and local ionospheric electric field E0;modification of the auroral arc and local spiral-like formation. However,some effects were observed only when the HF pump wave was reflected from theF2 layer. Among them are the generation of intense field-aligned ion outflows,and a strong increase in the electron temperature Te with altitude. Apossible scenario for the substorm triggering due to HF pumping into anauroral ionosphere is discussed. The authors present their interpretation ofthe data as follows. It is suggested that two populations of chargedparticles are at play. One of them is the runaway population of electronsand ions from the ionosphere caused by the effects of the powerful HF radiowave. The other is the population of electrons that precipitate from themagnetosphere. It is shown that the hydrodynamical equilibrium was disrupteddue to the effects of the HF pumping. We estimate that the parallel electricfield can reach values of the order of 30mV/m during substorm triggering

Phenomena in the ionosphere-magnetosphere system induced by injection of powerful HF radio waves into nightside auroral ionosphere