Articles | Volume 23, issue 5
Ann. Geophys., 23, 1585–1592, 2005

Special issue: Atmospheric studies by optical methods

Ann. Geophys., 23, 1585–1592, 2005

  27 Jul 2005

27 Jul 2005

Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic

M. J. Kosch3,2,1, T. Pedersen1, J. Hughes4, R. Marshall5, E. Gerken6, A. Senior2, D. Sentman4, M. McCarrick7, and F. T. Djuth8 M. J. Kosch et al.
  • 1Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AFB, Massachusetts, USA
  • 2Communication Systems, Lancaster University, Lancaster, UK
  • 3Honorary Research Fellow, University of Kwazulu-Natal, Durban, South Africa
  • 4Geophysical Institute, University of Alaska, Fairbanks, USA
  • 5STARLab, Stanford University, Stanford CA, USA
  • 6Dept. Electrical & Computer Engineering, Cornell University, Ithaca NY, USA
  • 7Advanced Power Technologies, Washington D.C., USA
  • 8Geospace Research, El Segundo CA, USA

Abstract. High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identical to natural aurora. Pumping at electron gyro-harmonic frequencies has special significance as many phenomena change their character. In particular, artificial optical emissions become strongly reduced for the third and higher gyro-harmonics. The High frequency Active Auroral Research Program (HAARP) facility is unique in that it can select a frequency near the second gyro-harmonic. On 25 February 2004, HAARP was operated near the third and passed through the second gyro-harmonic for the first time in a weakening ionosphere. Two novel observations are: firstly, a strong enhancement of the artificial optical emission intensity near the second gyro-harmonic, which is opposite to higher gyro-harmonics; secondly, the optical enhancement maximum occurs for frequencies just above the second gyro-harmonic. We provide the first experimental evidence for these effects, which have been predicted theoretically. In addition, irregular optical structures were created when the pump frequency was above the ionospheric critical frequency.

Keywords. Active experiments – Auroral ionosphere – Wave-particle interactions