Downshifted maximum features in stimulated electromagnetic emission spectra

Leyser, T. B.; Thidé, Bo; Waldenvik, M.; Veszelei, E.; Frolov, V. L.; Грач, С. М.; Комраков, Г. П.

doi:10.1029/94ja01399

Cited by 76 publications

(97 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The DM involves electrostatic lower hybrid waves, where the lower hybrid wave frequency is estimated to be ω lh 7.5 kHz. The presence of a DM and upshifted maximum (UM) in the SEE spectrum, which is closely correlated with FAIs, can also serve as a indicator of whether the pump frequency is near to or far from a harmonic of the electron gyro-frequency (Leyser et al, 1994). Another set of repeated daytime experiments shows the dependence of the DP on the pump frequency for different beam angles.…”

Section: Associated Wideband See and Irregularitiesmentioning

confidence: 99%

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Scales

Bernhardt

et al. 2015

Ann. Geophys.

View full text Add to dashboard Cite

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.

show abstract

Section: Associated Wideband See and Irregularitiesmentioning

confidence: 99%

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Scales

Bernhardt

et al. 2015

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

“…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%

“…Two proposed mechanisms for converting the UH waves to electromagnetic (EM) waves are (1) the parametric decay of the UH wave directly into an EM wave and a lower hybrid (LH) wave, and (2) a two-step process involving parametric decay of the UH wave into an electron Bernstein (EB) wave and a (LH) wave, followed by the generation of an EM wave by mode conversion of UH or EB waves on LH waves or striations. A model for the disappearance of the DM in the vicinity of the gyroharmonics [Leyser et al, 1994] involves the enhanced dispersion of UH waves in the vicinity of a gyroharmonic.…”

Section: Tionsmentioning

confidence: 99%

“…In these measurements, a receiver was assigned to the pump frequency, a second receiver was tuned to observe the DM, and the other receivers were tuned to a set of frequencies distributed within the BUM spectrum. The bandwidth of the receivers was 1 kHz, and their outputs were recorded on a six-channel high-speed recorder providing a temporal resolution of 0.1 s. Measurements of the DM were of particular interest since it indicates the presence of heater-induced small-scale irregularities with a cross-field scale lñ -< 50 m [Frolov, 1991;Leyser et al, 1994]. The narrowband receiver measurements are used to complement the spectrum analyzer measurements, which are the focus of this paper.…”

Section: Equipment and Facilities Descriptionmentioning

confidence: 99%

See 1 more Smart Citation

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.

Self Cite

View full text Add to dashboard Cite

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...

show abstract

“…Figure 3b, 3c, and 3d of Leyser et aL [1993], showing a peak downshifted 10-15 kHz from the HF frequency. Detailed features of the DM are described by Leyser et al [1993Leyser et al [ , 1994 The føllowing may be emphasized:…”

Section: Introductionmentioning

confidence: 99%

Theoretical model for long time stimulated electromagnetic emission generation in ionospheric radio modification experiments

Mjølhus¹

1998

J. Geophys. Res.

View full text Add to dashboard Cite

Abstract. Experimental evidence points toward magnetic-field-aligned small-scale plasma density striations as responsible for the long time features of stimulated electromagnetic emissions (SEE) in ionospheric radio modification experiments. This paper emphasizes that such striations act as resonators for the generation of trapped upper hybrid oscillations. The sidebands observed in long time SEE experiments are associated with nonstationary behavior, such as parametric instabilities, of these trapped oscillations. A theoretical model for this is formulated and studied numerically. Source spectra for SEE generation, consistent with the main properties of observed downshifted maximum and broad continuum features, will be presented. The first is associated with a trapped oscillations decay instability, while the latter is associated with cavitation in the pre-formed striations.

show abstract

Downshifted maximum features in stimulated electromagnetic emission spectra

Cited by 76 publications

References 29 publications

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

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

Theoretical model for long time stimulated electromagnetic emission generation in ionospheric radio modification experiments

Contact Info

Product

Resources

About