Unprecedentedly Strong and Narrow Electromagnetic Emissions Stimulated by High-Frequency Radio Waves in the Ionosphere

Norin, Lars; Leyser, T. B.; Nordblad, Erik; Thidé, Bo; McCarrick, M.

doi:10.1103/physrevlett.102.065003

Cited by 47 publications

(65 citation statements)

References 11 publications

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“…1 show a similar frequency shift and relative amplitude of Stokes and antiStokes lines when compared to experimental observations at HAARP (e.g. Norin et al, 2009;Bernhardt et al, 2009). The reflected pump waves and scattered electromagnetic waves combine to produce upshifted SBS lines with lower intensity and slightly higher 4-5 Hz frequency offset than the down- shifted SBS.…”

Section: Experiments Setupsupporting

confidence: 55%

“…However, due to updates of the HAARP facility in 2007, it has been possible to investigate narrowband (within roughly 1 kHz of the pump frequency) SEE near the resonance altitude in recent years. Stimulated Brillouin scattering (SBS) has been recently observed in the high-power, HF wave ionospheric experiments, shifted by a few tens of hertz from the pump frequency (Norin et al, 2009). During the past few years, SEE observations at HAARP have revealed a plethora of narrowband SEE lines associated with SBS and stimulated ion Bernstein scatter (SIBS) (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…During the past few years, SEE observations at HAARP have revealed a plethora of narrowband SEE lines associated with SBS and stimulated ion Bernstein scatter (SIBS) (e.g. Norin et al, 2009;Bernhardt et al, 2009Bernhardt et al, , 2010Samimi et al, 2012Samimi et al, , 2013Samimi et al, , 2014. further investigated SBS and SIBS and their interrelationship in detail over a range of aspect beam angles and frequency stepping near electron gyro-harmonics.…”

Section: Introductionmentioning

confidence: 99%

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Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Scales

Bernhardt

et al. 2015

Ann. Geophys.

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Abstract.Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, highpower, 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.

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Section: Experiments Setupsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Scales

Bernhardt

et al. 2015

Ann. Geophys.

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“…The spectra then immediately showed downshifted and upshifted emissions at harmonics of f ci as well as ion acoustic IA emission lines near 10 Hz. The discrete structures are attributed to SIBS instability and the IA emission lines are due to the Magnetized Stimulated Brillouin Scatter (MSBS) process [Norin et al, 2009;Bernhardt et al, 2009Bernhardt et al, , 2010. Figure 1 shows four snapshots of high resolution power spectrum for P heater = 0.1 MW, P heater = 0.7 MW, P heater = 2 MW, and P heater = 3.6 MW.…”

Section: Discrete Ion Gyro-features For F 0 3f Cementioning

confidence: 99%

“…The direct parametric decay instability can be distinguished by strong SEE spectral sidebands. Magnetized stimulated Brillouin scatter (MSBS) which involves decay of the EM pump wave into ion acoustic IA or electrostatic ion cyclotron (EIC) and a scattered EM wave is an example of the direct conversion [Norin et al, 2009;Bernhardt et al, 2009Bernhardt et al, , 2010. The other possible scenario is the conversion of the EM wave first to a high frequency ES wave and irregularities through the oscillating two stream instability (OTSI) [Dysthe et al, 1983;Huang and Kuo, 1995].…”

Section: Introductionmentioning

confidence: 99%

Ion gyro‐harmonic structuring in the stimulated radiation spectrum and optical emissions during electron gyro‐harmonic heating

et al. 2013

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[1] Stimulated electromagnetic emissions (SEEs) are secondary radiation produced during active space experiments in which the ionosphere is actively heated with high power high frequency (HF) ground-based radio transmitters. Recently, there has been significant interest in ion gyro-harmonic structuring the SEE spectrum due to the potential for new diagnostic information available such as electron acceleration and creation of artificial ionization layers. These relatively recently discovered gyro-harmonic spectral features have almost exclusively been studied when the transmitting frequency is near the second electron gyro-harmonic frequency. The first extensive systematic experimental investigations of the possibility of these spectral features for third electron gyro-harmonic heating are provided here. Discrete spectral features shifted from the transmit frequency ordered by harmonics of the ion gyro-frequency were observed for third electron gyro-harmonic heating for the first time at a recent campaign at the High Frequency Active Auroral Research Program (HAARP) facility. These features were also closely correlated with a broader band feature at a larger frequency shift from the transmit frequency known as the downshifted peak (DP). The power threshold of these spectral features was measured, as well as their behavior with heater beam angle, and proximity of the transmit frequency to the third electron gyro-harmonic frequency. Comparisons were also made with similar spectral features observed during second electron gyro-harmonic heating during the same campaign. A theoretical model is provided that interprets these spectral features as resulting from parametric decay instabilities in which the pump field ultimately decays into high frequency upper hybrid/electron Bernstein and low frequency neutralized ion Bernstein IB and/or obliquely propagating ion acoustic waves at the upper hybrid interaction altitude. Coordinated optical and SEE observations were carried out in order to provide a better understanding of electron acceleration and precipitation processes. Optical emissions were observed associated with SEE gyro-harmonic features for pump heating near the second electron gyro-harmonic during the campaign. The observations affirm strong correlation between the gyro-structures and the pump-induced optical emissions.

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Investigation of ionospheric stimulated Brillouin scatter generated at pump frequencies near electron gyroharmonics

et al. 2013

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[1] Stimulated Electromagnetic Emissions (SEEs), secondary electromagnetic waves excited by high power electromagnetic waves transmitted into the ionosphere, produced by the Magnetized Stimulated Brillouin Scatter (MSBS) process are investigated. Data from four recent research campaigns at the High Frequency Active Auroral Research Program (HAARP) facility is presented in this work. These experiments have provided additional quantitative interpretation of the SEE spectrum produced by MSBS to yield diagnostic measurements of the electron temperature and ion composition in the heated ionosphere. SEE spectral emission lines corresponding to ion acoustic (IA) and electrostatic ion cyclotron (EIC) mode excitation were observed with a shift in frequency up to a few tens of Hz from the pump frequency for heating near the third harmonic of the electron gyrofrequency 3f ce . The threshold of each emission line has been measured by changing the pump wave power. The excitation threshold of IA and EIC emission lines originating at the reflection and upper hybrid altitudes is measured for various beam angles relative to the magnetic field. Variation of strength of MSBS emission lines with pump frequency relative to 3f ce and 4f ce is also studied. A full wave solution has been used to estimate the amplitude of the electric field at the interaction altitude. The estimated instability threshold using the theoretical model is compared with the threshold of MSBS lines in the experiment and possible diagnostic information for the background ionospheric plasma is discussed. Simultaneous formation of artificial field-aligned irregularities (FAIs) and suppression of the MSBS process is investigated. This technique can be used to estimate the growth time of artificial FAIs which may result in determination of plasma waves and physical process involved in the formation of FAIs.Citation: Mahmoudian, A., W. A. Scales, P. A. Bernhardt, H. Fu, S. J. Briczinski, and M. J. , Investigation of ionospheric stimulated Brillouin scatter generated at pump frequencies near electron gyroharmonics, Radio Sci., 48,[685][686][687][688][689][690][691][692][693][694][695][696][697]

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Unprecedentedly Strong and Narrow Electromagnetic Emissions Stimulated by High-Frequency Radio Waves in the Ionosphere

Cited by 47 publications

References 11 publications

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Ion gyro‐harmonic structuring in the stimulated radiation spectrum and optical emissions during electron gyro‐harmonic heating

Investigation of ionospheric stimulated Brillouin scatter generated at pump frequencies near electron gyroharmonics

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