Observations of fluxes of suprathermal electrons accelerated by HF excited instabilities

Carlson, H. C.; Wickwar, Vincent B; Mantas, G. P.

doi:10.1016/0021-9169(82)90020-4

Cited by 106 publications

(91 citation statements)

References 24 publications

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“…HF-excited airglow enhancements were first reported at 630.0 nm (Sipler and Biondi, 1972) where they are most easily seen, but they can be and are found in HF experiments, due to both thermal and accelerated electrons (Carlson, 2002 suprathermal electrons. These suprathermal electrons produce enhanced optical emissions at 557.7 (Bernhardt et al, 1989;Pedersen et al, 2003), 777.4 (Carlson, 2002Djuth et al, 2005), 844.6 (Gustavsson et al, 2005), 427.8 (Holma et al, 2006), 660.0 (Djuth et al, 1999) which can complement thermal excitation of 630.0 nm optical emissions (Carlson, 2002), and are also seen directly in enhanced incoherent scatter radar plasma lines (Carlson et al, 1982).…”

Section: Discussionmentioning

confidence: 99%

“…(2) A GW ERP HF facility would deliver about of ∼10 −7 W cm −2 near the F-region peak altitude. (3) The efficiency of conversion of HF energy to the electron energy accelerated above the ionization threshold for effective ionization production (taking ∼30 eV per ionization) was established by Carlson et al (1982) to be order 10% at order 100 MW ERP. (4) With judicious selection of future operating modes, comparable efficiencies should be realizable, and appreciable production of ionization should be seen.…”

Section: Discussionmentioning

confidence: 99%

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Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

Blagoveshchenskaya

Carlson²,

Kornienko

et al. 2009

Ann. Geophys.

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Abstract. Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency f H was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ). The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the LondonTromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland), the European Incoherent Scatter (EIS-CAT) UHF radar at Tromsø and the Tromsø ionosonde (dynasonde). The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation of Correspondence to: N. F. Blagoveshchenskaya (nataly@aari.nw.ru) striations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

Blagoveshchenskaya

Carlson²,

Kornienko

et al. 2009

Ann. Geophys.

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“…At Arecibo the geomagnetic field has a zenith angle of about 45 • , a significantly different geometry than in the higher-latitude locations where the scanning observations discussed here have been carried out (Isham et al, 2000). Evidence for the existence of energetic electrons accelerated during RF pumping is also provided by Arecibo incoherent scatter radar (ISR) observations of RF-enhanced natural plasma lines (Carlson et al, 1982;Gurevich et al, 2000).…”

Section: Optical Emissionsmentioning

confidence: 93%

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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“…These waves heat the plasma (a 250-300% enhancement of the electron temperature can be achieved) and accelerate elecCorrespondence to: S. M. Grach (sg@nirfi.sci-nnov.ru) trons up to energies of 5-30 eV (Carlson et al, 1982;Leyser et al, 2000). Recently, Gustavson et al (2005) found some evidence of electron acceleration up to 60 eV.…”

Section: Introductionmentioning

confidence: 99%

On the location and structure of the artificial 630-nm airglow patch over Sura facility

et al. 2007

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Abstract.Results are presented of the artificial optical emission of the atomic oxygen red line (the radiation of level O( 1 D) with a wavelength of 630 nm) from the HF-pumped ionosphere, obtained in September 2004 at the SURA heating facility situated near Nizhny Novgorod, Russia. For vertical pumping the airglow patch was increasingly displaced to the north, up to 7-8 • , with increasing reflection altitude. For large brightness of the emission, the airglow patch started to develop at the northern edge of the pump beam and later expanded to the south. These effects are attributed to the precipitation of supra-thermal electrons from the pump wave upper hybrid resonance altitude to lower altitudes where excitation of the O( 1 D) level is more effective due to the larger density of atomic oxygen, and the O( 1 D) lifetime is shorter. For a pump beam inclination of 12 • to the south, the optical spot was displaced by 4-5 • to the south relative to the straight-line projection of the pump beam onto the sky. This exceeds that expected from the ray tracing and may be related, most probably, to the so-called "magnetic zenith" effect. In addition, mid-scale (1-10 km) magnetic field-aligned structures were observed in the pumped volume of the ionosphere. The east-west motions of the airglow patches are also analyzed.

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Observations of fluxes of suprathermal electrons accelerated by HF excited instabilities

Cited by 106 publications

References 24 publications

Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

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

On the location and structure of the artificial 630-nm airglow patch over Sura facility

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