Articles | Volume 33, issue 8
Ann. Geophys., 33, 983–990, 2015
Ann. Geophys., 33, 983–990, 2015

Regular paper 11 Aug 2015

Regular paper | 11 Aug 2015

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

H. Y. Fu1, W. A. Scales2, P. A. Bernhardt3, S. J. Briczinski3, M. J. Kosch4,7, A. Senior4, M. T. Rietveld5, T. K. Yeoman6, and J. M. Ruohoniemi2 H. Y. Fu et al.
  • 1Key Laboratory for Information Science of Electromagnetic Waves (MoE) and School of Information Science and Technology, Fudan University, Shanghai, China
  • 2Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, USA
  • 3Plasma Physics Division, Naval Research Laboratory, Washington, DC, USA
  • 4Department of Physics, Lancaster University, Lancaster, UK
  • 5EISCAT Scientific Association, Ramfjordmoen, Norway
  • 6Department of Physics and Astronomy, University of Leicester, Leicester, UK
  • 7South African National Space Agency, Hermanus, South Africa

Abstract. Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

Short summary
This paper reports the first experimental observation of stimulated Brillouin scattering near the third electron gyro-harmonic induced by high-frequency, high-power radio waves at EISCAT. The stimulated Brillouin scattering has also been correlated with simultaneous observations of the field-aligned irregularities and electron temperature. The observed stimulated Brillouin scattering becomes enhanced for pumping near electron gyro-harmonics.