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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 7
Ann. Geophys., 27, 2699-2710, 2009
https://doi.org/10.5194/angeo-27-2699-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 2699-2710, 2009
https://doi.org/10.5194/angeo-27-2699-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  07 Jul 2009

07 Jul 2009

Radar observations of artificial E-region field-aligned irregularities

E. Nossa1, D. L. Hysell1, C. T. Fallen2, and B. J. Watkins2 E. Nossa et al.
  • 1Earth and Atmospheric Science, Cornell University, Ithaca, NY, USA
  • 2Geophysical Institute, University of Alaska, Fairbanks, AK, USA

Abstract. Artificial E region field aligned plasma density irregularities (FAIs) were generated using HAARP in four different experimental modes and observed with a coherent scatter radar imager located 450 km to the southwest where it could detect field-aligned backscatter. The experiments were conducted in July of 2008, during the Polar Aeronomy and Radio Science Summer School (PARS), during quiet conditions in the daytime when the E layer was dense and absorption was modest. The echoes observed during zenith and magnetic zenith heating experiments were deflected from their nominally anticipated horizontal positions toward the midpoint position. The occurrence of hysteresis when heating with amplitude modulated pulses implied the development of the resonance instability, although the threshold for the onset of instability appeared to be higher than what has been predicted theoretically. Heating experiments involving pump frequencies slightly above and below the second electron gyroharmonic frequency produced no significant differences in the observed echoes. Finally, heating with a pump frequency slightly above the E region critical frequency appears to have produced FAIs at two distinct altitudes where the upper-hybrid resonance condition could be satisfied.

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