Spectral features of stimulated electromagnetic emission, measured in the 4.3–9.5 MHz pump wave frequency range

Frolov, V. L.; Сергеев, Е. Н.; Ermakova, E. N.; Комраков, Г. П.; Stubbe, P.

doi:10.1029/2001gl013251

Cited by 53 publications

(54 citation statements)

References 12 publications

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“…Such turbulence can consist of either Langmuir and ion-acoustic waves (Langmuir turbulence) or upper and lower hybrid waves (upper-hybrid turbulence). Previous studies, based on SEE, anomalous absorption, and electron temperature measurements, indicate that there is a minimum in the level of upper-hybrid excitation at the gyroharmonic frequencies (Stubbe et al, 1994;Robinson et al, 1996;Frolov et al, 1998Frolov et al, , 2001Mjølhus, 1998). More recently, both airglow and coherent backscatter radar signals have been shown to vanish when the pump frequency is tuned to the third gyroharmonic (Kosch et al, 2002a), supporting the role of upper-hybrid turbulence as the source of the energetic electrons.…”

Section: Optical Emissionsmentioning

confidence: 84%

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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Section: Optical Emissionsmentioning

confidence: 84%

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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“…The geomagnetic field plays a dominant role in SEE, as evidenced by the morphology of the SEE spectrum, which depends dramatically on the proximity of the HF pump frequency to a harmonic of the local electron gyrofrequency (Honary et al, 1999;Frolov et al, 2001). These properties suggest that features in the SEE spectrum should also depend on geomagnetic aspect angle (Isham et al, 2005), a topic that is investigated in this report.…”

Section: Stimulated Electromagnetic Emissionmentioning

confidence: 99%

Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer

et al. 2006

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Abstract.A high frequency (HF) ionospheric modification experiment was carried out between 25 September and 8 October 2004, using the EISCAT HF transmitter located near Tromsø, Norway. During this experiment the spectra of the stimulated HF sideband waves (stimulated electromagnetic emission or SEE) induced by the HF pump were observed using an interferometer consisting of three spaced receiving antennas with baselines both along and perpendicular to the meridian, and a multi-channel coherent receiver, installed in the vicinity of the HF facility. The transmitter operated at 4040 kHz and its antenna beam was scanned to angles of 0 • , 7 • , 14 • , and 21 • south from vertical, pausing 4 min at each position. This paper focuses on features of the downshifted peak (DP) emission, which has not been as thoroughly studied as many of the other SEE spectral features observable within the EISCAT pump frequency range. It was found that the signal-weighted direction of the DP source region remained within 5 • of magnetic zenith as the HF beam was tilted between 0 and 21 • south of vertical.

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Section: ³õóöíõöóâ ôòçíõóñä ëôíöôôõäçððñåñ óâAeëñëêîöúçðëâ ëñðñô×çóþmentioning

confidence: 99%

Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves

Грач¹,

Сергеев²,

Мишин³

et al. 2016

Phys.-Usp.

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A review is given of the current state-of-the-art of experimental studies and the theoretical understanding of nonlinear phenomena that occur in the ionospheric F-layer irradiated by high-power high-frequency ground-based transmitters. The main focus is on the dynamic features of high-frequency turbulence (plasma waves) and low-frequency turbulence (density irregularities of various scales) that have been studied in experiments at the Sura and HAARP heating facilities operated in temporal and frequency regimes specially designed with consideration of the characteristic properties of nonlinear processes in the perturbed ionosphere using modern radio receivers and optical instruments. Experimental results are compared with theoretical turbulence models for a magnetized collisional plasma in a high-frequency electromagnetic field, allowing the identification of the processes responsible for the observed features of artificial ionospheric turbulence.

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Spectral features of stimulated electromagnetic emission, measured in the 4.3–9.5 MHz pump wave frequency range

Cited by 53 publications

References 12 publications

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

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

Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer

Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves

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