Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

• Published in: Annales Geophysicae
• Main Authors: Fu, Haiyang, Scales, Wayne A., Bernhardt, Paul A., Briczinski, Stan J., Kosch, Michael J., Senior, Andrew, Rietveld, Michael T, Yeoman, Timothy Kenneth, Ruohoniemi, J. Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2015
• Subjects: Ionosphere; active experiments; particle acceleration; plasma waves and instabilities; VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Rom- og plasmafysikk: 437; VDP::Mathematics and natural science: 400::Physics: 430::Space and plasma physics: 437; EISCAT
• Online Access: https://hdl.handle.net/10037/8722; https://doi.org/10.5194/angeo-33-983-2015

Published version. Source at http://doi.org/10.5194/angeo-33-983-2015 . 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.