Observations of Stimulated Scattering of a Strong High-Frequency Radio Wave in the Ionosphere

Thidé, Bo; Kopka, H.; Stubbe, P.

doi:10.1103/physrevlett.49.1561

Cited by 243 publications

(116 citation statements)

References 11 publications

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“…These emissions are produced by the HF pump wave at an altitude close to the reflection height. The first observation of this phenomena was made by Thidé et al [1982] near Tromsø, and since then, many structures have been observed within the SEE spectra [Leyser, 2001]. The most common feature is the continuum which contains a peak found at the pump frequency f 0 with an often highly asymmetric broad upshifted and downshifted width.…”

Section: Introductionmentioning

confidence: 99%

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

et al. 2013

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[1] We test the existing theories regarding the thresholds for the parametric decay instability (PDI), the oscillating two-steam instability (OTSI), and the thermal parametric instability (TPI) using the European Incoherent Scatter (EISCAT) facility's ionospheric heater. In these processes, the pump wave can couple to various electrostatic waves in the F layer ionosphere, which can be observed using the EISCAT UHF radar (PDI and OTSI) or by HF radar (TPI). On 19 October 2012, the heater power was stepped from 0.5 MW to 100 MW effective radiated power in seven steps using a 1 min on, 1 min off cycle. We use an electric field model, taking into account D region absorption, to compare theory with our observations. In all three cases, we find good agreement. In addition, the growth of striations formed during the TPI causes anomalous absorption of the heater wave, which we observe as decreased UHF ion line and plasma line backscatter power. We show evidence that heating for a prolonged period of time reduces the UHF ion line intensity throughout the experiment.Citation: Bryers, C. J., M. J. Kosch, A. Senior, M. T. Rietveld, and T. K. Yeoman (2013), The thresholds of ionospheric plasma instabilities pumped by high-frequency radio waves at EISCAT,

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Section: Introductionmentioning

confidence: 99%

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

et al. 2013

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“…SEE was discovered and has most often been measured using a spectrum analyzer connected to an HF receiving antenna (Thidé et al, 1982;Stubbe et al, 1984). Although spectrum analyzers provide only moderate (several-second) time resolution, they have the large, 120-dB or greater dynamic range sometimes required to detect the weak SEE signals lying near the ionospherically-reflected (and possibly ground-path-propagated) pump wave, which may have 100-dB-greater power than the SEE sidebands.…”

Section: Techniquementioning

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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“…This technique has also been used extensively to investigate the charged dust layers in the mesosphere [Chilson et al, 2000;Havnes et al, 2003;Mahmoudian et al, 2011;Mahmoudian and Scales, 2012]. High power electromagnetic waves transmitted from the ground interact with the local plasma in the ionosphere and can produce stimulated electromagnetic emissions (SEEs) through the parametric decay instability [Thide et al, 1982]. The interaction of the injected radio beam with local plasma may generate different types of waves, instabilities, and turbulence, and as a result a variety of spectral features in the scattered wave are expected.…”

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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Observations of Stimulated Scattering of a Strong High-Frequency Radio Wave in the Ionosphere

Cited by 243 publications

References 11 publications

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

The thresholds of ionospheric plasma instabilities pumped by high‐frequency radio waves at EISCAT

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

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

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