High‐latitude pump‐induced optical emissions for frequencies close to the third electron gyro‐harmonic

Kosch, M. J.; Rietveld, M. T.; Kavanagh, A. J.; Davis, C. J.; Yeoman, T. K.; Honary, F.; Hagfors, T.

doi:10.1029/2002gl015744

Cited by 58 publications

(84 citation statements)

References 31 publications

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“…Whilst the pump frequency does not appear important, pump power determines the electron temperature enhancement and plasma depletion depth in their model. However, we note that with a pump frequency of 2.85 MHz HAARP produces an O1D optical emission of 100 -300 R for 11 MW ERP Kosch et al, 2005], whereas for pump frequencies >4 MHz EISCAT produces O1D optical intensities of order 100 R for pump powers of 70-200 MW ERP [Kosch et al, 2000[Kosch et al, , 2002bRietveld et al, 2003]. Since the O1D 630 nm pumpinduced optical emission is at least partly a function of electron temperature [e.g., Ashrafi et al, 2006;Gustavsson et al, 2002], we conclude that low pump powers at HAARP are compensated by pumping the ionosphere near the second electron gyroharmonic, which seems to produce significant electron temperature enhancements.…”

Section: Resultsmentioning

confidence: 99%

“…However, the Kodiak SuperDARN radar, which is sensitive to 10 m scale irregularities, did show natural background backscatter ($30 -35 dB), which was significantly enhanced by pumping ($50-60 dB) [Kosch et al, 2007] (not shown). Such natural backscatter at HAARP around sunset and pump-enhanced backscatter [e.g., Kosch et al, 2002b] are common. Obviously, the irregularities make for a nonideal reflecting surface and real flux density gain is most likely less than 30 dB.…”

Section: Resultsmentioning

confidence: 99%

“…During artificial optical emission experiments at EISCAT ] artificial plasma cavities with depletions of $10-20% have been observed (M. T. Rietveld, private communication, 2006). Similarly, also during artificial optical emission experiments at EISCAT [Kosch et al, 2002b], HF radio images of ionosonde backscatter often showed significant clustering around the magnetic zenith (M. T. Rietveld, private communication, 2006). This has been confirmed by Djuth et al [2006] who found preferential production of large-scale plasma irregularities in the magnetic zenith over HAARP.…”

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

et al. 2007

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[1] On 4 February 2005 the High-Frequency Active Auroral Research Program (HAARP) facility was operated at 2.85 MHz to produce artificial optical emissions in the ionosphere while passing through the second electron gyroharmonic. All-sky optical recordings were performed with 15 s integration, alternating between 557.7 and 630 nm. We report the first optical observations showing the temporal evolution of large-scale pump wave selffocusing in the magnetic zenith, observed in the 557.7 nm images. These clearly show that the maximum intensity was not reached after 15 s of pumping, which is unexpected since the emission delay time is <1 s, and that the optical signature had intensified in a much smaller region within the beam after 45 s of pumping. In addition, adjacent regions within the beam lost intensity. Radar measurements indicate a plasma depletion of $1% near the HF reflection altitude. Ray tracing of the pump wave through the plasma depletion region, which forms a concave reflecting radio wave mirror, reproduces the optical spatial morphology. A radio wave flux density gain of up to $30 dB may occur. In addition, the ray trace is consistent with the observed artificial optical emissions for critical plasma frequencies down to $0.5 MHz below the pump frequency.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

et al. 2007

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“…Artificially enhanced airglow due to excitation of oxygen atoms by accelerated electrons was also reported at Arecibo, Puerto Rico, by Gordon and Carlson [1974]. The electron acceleration is due to modified electron distributions by plasma waves such as Langmuir waves [Weinstock, 1975;Isham et al, 1999aIsham et al, , 1999b or UH resonance in the more recent study by Kosch et al [2002]. Optical observations were carried out with multiple wideand narrow-field systems at the HAARP site observing 557.7 and 630.0 nm emissions from atomic oxygen corresponding to >4.17 and >1.96 eV electron energy, respectively, and 427.8 nm N + 2 emissions indicating ionization production at >18 eV.…”

Section: Ion Gyro-features and Pump-induced Opticalmentioning

confidence: 89%

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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“…Coherent radar aspect angle variation and scintillation of satellite and radio source signals have been used in the past to study artificially-created field-aligned irregularities at a number of locations around the world (Frolov, 2003), but work on the aspect angle variation of electron temperature enhancements, Langmuir turbulence, RF-induced optical emissions, and stimulated electromagnetic emissions (SEE) has only relatively recently begun (Isham et al, 1999a, c;Kosch et al, 2000;Mishin et al, 2001;Pedersen et al, 2003;Rietveld et al, 2003;Frolov and Nedzvedski, 2004;Kosch et al, 2004;Frolov et al, submitted, 2004 1 Groves, private communication, 2003). The Sura facility (56.13 N latitude, 46.10 E longitude) transmits between 4.3 and 9.5 MHz with a maximum frequency-dependent ERP of between 80 and 280 MW, respectively (V. Frolov and E. Sergeev, private communications, 2003).…”

Section: Introduction and Summary Of Recent Aspect Angle Resultsmentioning

confidence: 99%

An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra

Isham¹,

Hagfors

Khudukon

et al. 2005

Ann. Geophys.

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Abstract. When the Earth's ionosphere is irradiated by a radiofrequency (RF) electromagnetic wave of sufficiently high power density and tuned to match a natural E-or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structureCorrespondence to: B. Isham (bisham@bc.inter.edu) in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in view of the not yet understood but complex relationship between electrostatic fluctuations and SEE, it is of interest to investigate experimentally whether a similar angular structure is present in the various spectral features of the SEE signals and to compare the results with radar and other observations of RF-pump-induced effects. To this end we describe a simple two-element radio interferometer designed to search for aspect angle dependence of SEE features. We present an example of the initial data produced by this system, and draw preliminary conclusions based on the example data.

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High‐latitude pump‐induced optical emissions for frequencies close to the third electron gyro‐harmonic

Cited by 58 publications

References 31 publications

Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

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

An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra

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