Detection of artificially generated ULF waves by the FAST spacecraft and its application to the “tagging” of narrow flux tubes

Abstract

Recently, Robinson et al. [2000] presented a brief report on the artificial generation of ULF waves by high power ionospheric modification and their subsequent detection by the Fast Auroral Snapshot (FAST) spacecraft. The radio frequency “heating” facility at Tromsø was employed to impose a 3‐Hz modulation on the current system that constitutes the auroral electrojet, resulting in the injection of field‐guided ULF waves into the magnetosphere. The electric and magnetic field signatures of the waves were detected directly by the FAST spacecraft. Furthermore, a signature in the downgoing field‐aligned electron flux, also observed by the satellite, was postulated to have resulted from the interaction of the ULF waves with the upper boundary of the ionospheric Alfvén resonator. This paper evaluates these results in the context of the prevailing ionospheric conditions during the experiment and discusses the significance of the substorm activity, which occurred during this interval. The technique of artificial ULF wave injection, which can be used to “tag” narrow flux tubes, could play an important part in overcoming mapping issues between ground‐based and space‐based observations of phenomena that couple the ionosphere and magnetosphere.