Ionospheric heater beam scanning: A new technique for ELF studies of the auroral ionosphere


  • M. T. Rietveld,

  • R. Barr,

  • H. Kopka,

  • E. Nielsen,

  • P. Stubbe,

  • R. L. Dowden


ELF/VLF wave generation by modulation of the auroral electrojet has previously been performed near Tromsø, Norway, with an HF heating beam pointed in a fixed (zenith) direction. By varying the phases of the HF waves transmitted from adjacent rows of antennas in the transmitting antenna array, the beam direction can now be scanned in the north-south plane at frequencies from zero to approximately 5 kHz. In one type of beam scanning the amplitude of the heating beam is ELF modulated while the beam direction is simultaneously swept slowly, in sawtooth fashion, about the zenith. Variations in the ELF field strength, measured on the ground as the source is swept in this manner, are shown to be associated with spatial variations of the auroral ionosphere in the north-south direction. We compare these spatial variations with those observed by STARE.