The 3‐D Distribution of Artificial Aurora Induced by HF Radio Waves in the Ionosphere

Abstract

We present 3‐D excitation rate estimates of artificial aurora in the ionospheric F layer, induced by high‐frequency radio waves from the European Incoherent Scatter heating facility. Simultaneous imaging of the artificial aurora was done with four separate Auroral Large Imaging System stations, permitting tomography‐like 3‐D auroral reconstruction of the enhanced atomic oxygen emissions at 6,300, 5,577, and 8,446 Å. Inspection of the 3‐D reconstructions suggests that the distribution of energized electrons is less extended in altitude than predicted by transport calculations of electrons accelerated to 2–100 eV. A possible reason for this discrepancy is that high‐frequency pumping might induce an anisotropic distribution of energized electrons.