Results of the experimental study of narrow continuum features in stimulated ionospheric emission spectra

Frolov, V. L.; Комраков, Г. П.; Сергеев, Е. Н.; Thidé, Bo; Waldenvik, M.; Veszelei, E.

doi:10.1007/bf02676524

Cited by 17 publications

(26 citation statements)

References 9 publications

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“…Possible mechanisms for the production of the DM, the BC, and the NC have received a great deal of attention in the literature [Leyser et al, 1993[Leyser et al, , 1994Stubbe et al, 1994;Shyarts et al, 1994;Frolov et al, 1997a]. The fact that these SEE features are either primarily or entirely downshifted from the pump frequency restricts the set of interactions that might possibly be involved in their generation [Stubbe et al, 1984].…”

Section: Tionsmentioning

confidence: 99%

Effect of ionospheric self‐conditioning and preconditioning on the broad upshifted maximum component of stimulated electromagnetic emission

Wagner¹,

Bernhardt²,

Goldstein³

et al. 1999

J. Geophys. Res.

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Abstract. Stimulated electromagnetic emissions (SEE) are high-frequency radio emissions that are generated during high-power, high-frequency, ordinary mode (O-mode), radiowave heating of the ionosphere. These emissions are particularly useful in ionospheric heating experiments because they provide a way of monitoring space plasma processes remotely and passively. In order to utilize these emissions for diagnostic purposes, it is necessary to understand the space plasma processes involved in their generation. The purpose of these experiments was to observe the responses of a particular component of the SEE, the broad upshifted maximum (BUM), to a variety of heating stimuli in an effort to understand the factors involved in its development. Heating experiments were conducted at the Radiophysical Research Institute SURA Ionospheric Modification Facility in Russia. Experiments consisted of single-pump, two-pump, and single-pump power-stepping experiments. The single-pump and two-pump transmissions were organized into groups of pulses of varying widths and spacings to facilitate the investigation of self-conditioning, preconditioning, and two-pump-interaction conditioning effects. The major findings of these experiments are that the action of a pump can have a conditioning effect on the medium that affects the time development of the BUM. The result of the conditioning process is the formation of an overshoot in the temporal development of the BUM. A residual conditioning effect is sustained after the end of a pump pulse for a period of time (-30 s). The residual conditioning acts as preconditioning for the BUM of a subsequent pump pulse. A second O-mode pump (pump2), at a frequency a few hundred kilohertz above that of the first pump (pump 1), is observed to cause additional suppression of the pumpl BUM, implying an enhanced conditioning effect. Time constants for the buildup and decay of the conditioning effects are estimated. During power-stepping experiments, the BUM spectrum was observed to evolve from a weak, narrow spectrum at an effective radiated power (ERP) of •5 MW, to a strong, broad spectrum with a ramp-like spectral tail at an ERP of •150 MW. Other features noted during power stepping include (1) strong BUM transients at pump power level transitions, (2) BUM amplitude asymmetry between power-up and power-down sides of a power stepping cycle, (3) reduction of the BUM spectral peak offset from the pump frequency with increasing pump power, and (4) power law dependence of BUM power on pump power (exponent -2). Results of these experiments are used in an attempt to assess the relevance of small-scale irregularity generation and electron heating mechanisms to the observed conditioning effects. IntroductionStimulated electromagnetic emissions (SEE) are highfrequency (HF) radio emissions that are generated as a result of a complicated series of interactions between a high-power, ordinary mode (O-mode), HF radiowave pump (the heater), and internal plasma waves in the ionized upper atmosphere.•Now at Laurel, Mar...

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Section: Tionsmentioning

confidence: 99%

Effect of ionospheric self‐conditioning and preconditioning on the broad upshifted maximum component of stimulated electromagnetic emission

Wagner¹,

Bernhardt²,

Goldstein³

et al. 1999

J. Geophys. Res.

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“…The BC characteristics were considered in [4,11,15,20,33]. In addition, we will use the narrow continuum (NC), a narrow-band SEE component, observed at small negative detunings with respect to the PW frequency [3,[34][35][36]. Some notes will also be made on the characteristics of the up-shifted maximum (UM), i.e., the narrow-band emission maximum located in the region of positive detunings ∆f ≈ 10 kHz almost symmetrically to the DM with respect to the PW frequency [4,24,37].…”

Section: Brief Description Of the See Diagnostic Features Used For Prmentioning

confidence: 99%

Experimental Studies of the Effects Observed During the Nonlinear Interaction of Two High-Power Radio Waves in a Magnetoplasma

Frolov

Сергеев

Thidé

et al. 2005

Radiophys Quantum Electron

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We present the results of experiments on modification of the ionospheric F region by two highpower (P eff ≈ 20 MW) O-mode electromagnetic waves. The experiments were performed at the "Sura" heating facility of the Radiophysical Research Institute (Nizhny Novgorod, Russia) in May 23-27, 1993 at the pump frequencies near the 4th, 5th, or 6th harmonics of the electron gyrofrequency. Ionospheric perturbations were diagnosed by measuring the stationary spectral characteristics of the stimulated electromagnetic emission (SEE) of the ionospheric plasma. We determine the features of variation in the spectral characteristics of particular SEE components during the simultaneous heating of the ionospheric plasma by two radio waves in comparison with the case of a monochromatic pump wave. We observed the effect of enhanced generation of the broad up-shifted maximum (BUM) by the higher-frequency pump wave. This is accompanied by strong suppression of the BUM induced by the lower-frequency pump wave. It is shown that the effects observed during the two-frequency heating of the ionosphere have well pronounced gyroharmonic properties, i.e., depend on both the electron-gyroharmonic number and the frequency detuning of the pump waves from a harmonic of the electron gyrofrequency. We also pointed out that a change in the properties of artificial small-scale ionospheric irregularities (striations) excited by high-power radio waves is not the cause of a change in the properties of the down-shifted maximum and the BUM during the two-frequency modification of the ionospheric plasma. Ways for the further development of these studies are discussed.

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“…(v) striction narrow-band radiation component, or ponderomotive narrow continuum NC p , which is observed for detunings of up to ∆f − ≈ 30−50 kHz at the stage of striction parametric instability development [8,9,16]; (vi) broadband radiation, which is similar to BUM and is detected in frequency ranges between the gyroharmonics, or broad upshifted structure (BUS) [19]. By tradition and to avoid therminological mess, we will use the above-mentioned English-language names of the radiation components.…”

Section: Introductionmentioning

confidence: 98%

“…According to the studies performed in the middle [3][4][5][6][7][8][9] and polar [1,[10][11][12][13][14] latitudes, the SEE in its stationary state, which is usually reached a few seconds (or a few tens of seconds) after the interaction begins, is a composition of more than ten separate spectral structures (radiation components), which is evidence for the variety of the plasma processes occurring simultaneously in the perturbed region (PR) of the ionosphere. An overview of the results obtained in these experiments is given in, e.g., [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Properties of the thermal narrow-continuum component in the spectrum of stimulated ionospheric emission

Frolov

Nedzvetsky

Сергеев

et al. 2005

Radiophys Quantum Electron

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We present the results of experimental studies of the properties of the thermal narrow-continuum component NC th of stimulated electromagnetic emission (SEE) of the ionosphere observed in a narrow region between the pump frequency and the downshifted maximum (DM). Spectral and dynamic characteristics of the NC th component are considered and the dependence of its properties on the frequency and power of the pumping wave as well as on the zenith angle of a high-power radio-wave beam in the geomagnetic-meridian plane is analyzed. It is proved that the NC th generation is determined by the thermal (resonant) parametric instability near the level of the upper-hybrid resonance for a high-power radio wave. New experimental data on the properties of the main DM thermal component in the spectrum of stimulated electromagnetic emission, which we used as the reference component in most measurements, are presented.

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Results of the experimental study of narrow continuum features in stimulated ionospheric emission spectra

Cited by 17 publications

References 9 publications

Effect of ionospheric self‐conditioning and preconditioning on the broad upshifted maximum component of stimulated electromagnetic emission

Effect of ionospheric self‐conditioning and preconditioning on the broad upshifted maximum component of stimulated electromagnetic emission

Experimental Studies of the Effects Observed During the Nonlinear Interaction of Two High-Power Radio Waves in a Magnetoplasma

Properties of the thermal narrow-continuum component in the spectrum of stimulated ionospheric emission

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