FAST observations of ULF waves injected into the magnetosphere by means of modulated RF heating of the auroral electrojet

Results are reported from an experiment in which the HF high power facility at Tromsø was utilised to inject artificial ULF waves into the magnetosphere by means of modulated heating of the auroral electrojet. Local electric field oscillations associated with the artificially stimulated ULF waves were detected on board the FAST spacecraft, at an altitude of 2550 km. In addition, a modulated downward flux of electrons was also detected. The artificially excited waves, together with these energised downward electrons, were observed in a narrow region only a few tens of km across the geomagnetic field, which mapped down the geomagnetic field line to the heated volume in the ionosphere. Furthermore, the downward flux exhibited energy dispersion in a manner that was consistent with the artificially excited waves having followed the geomagnetic field line out beyond the spacecraft, where they appear to have stimulated electron precipitation back down the field line.

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