Stimulated electromagnetic emission near electron cyclotron harmonics in the ionosphere

Leyser, T. B.; Thidé, Bo; Derblom, H.; Hedberg, Å.; Lundborg, Bengt; Stubbe, P.; Kopka, H.

doi:10.1103/physrevlett.63.1145

Cited by 122 publications

(112 citation statements)

References 16 publications

Supporting

Mentioning

110

Contrasting

Order By: Relevance

“…The behavior of the BUM relative to the presence or absence of striations is more ambiguous. The BUM appears continuously over a range of pump frequencies starting at -10 kHz below the gyroharmonic frequency [Frolov et al, 1996] and continuing to a maximum frequency (fpmx) --100 kHz above the gyroharmonic frequency [Thid• et al, 1983;Stubbe et al, 1984Stubbe et al, , 1994Leyser et al, 1989Leyser et al, , 1990Leyser et al, , 1993Frolov et al, 1996]. Over this range of pump frequencies, striations are present everywhere except for a narrow range of frequencies surrounding the gyroharmonic frequency.…”

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.

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

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.

View full text Add to dashboard Cite

show abstract

“…Even if the observed spectra are highly reproducible, they depend strongly on the applied HF frequency. In the work of Leyser et al [1989] it was reported that several of the prominent spectral features are absent when the applied frequency is near a harmonic of the electron gyrofrequency. After that, emphasis has been put on the possible role of smallscale magnetic field-aligned density striations, which are known to be generated in these experiments [Fialer, 1974;Minkoff et al, 1974;Djuth et al, 1985].…”

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

“…Finally the high frequency ES wave scatters from irregularities back into the EM wave measured on the ground. The downshifted maximum (DM), a distinct peak at a frequency approximately 10 kHz below the pump [Leyser, 2001] involving electrostatic lower hybrid waves is believed to be produced through this mechanism [Bernhardt et al, 1994;Huang and Kuo, 1995;Leyser et al, 1989Leyser et al, , 1990.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

[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.

show abstract

Stimulated electromagnetic emission near electron cyclotron harmonics in the ionosphere

Cited by 122 publications

References 16 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

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

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

Contact Info

Product

Resources

About