Temporal and spatial power spectrum studies of numerical simulations of Type II gradient drift irregularities in the equatorial electrojet

Keskinen, M. J.; Sudan, R. N.; Ferch, R. L.

doi:10.1029/ja084ia04p01419

Cited by 103 publications

(61 citation statements)

References 31 publications

(65 reference statements)

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“…These predictions were admirably verified by the numerical simulations of Keskinen et al [1979]. These predictions were admirably verified by the numerical simulations of Keskinen et al [1979].…”

Section: Fn • Flvak•'ln •/•'supporting

confidence: 64%

Unified theory of Type I and Type II irregularities in the equatorial electrojet

Sudan¹

1983

J. Geophys. Res.

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Section: Fn • Flvak•'ln •/•'supporting

confidence: 64%

Unified theory of Type I and Type II irregularities in the equatorial electrojet

Sudan¹

1983

J. Geophys. Res.

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259

246

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“…The phase velocity of the secondary waves is significantly more difficult to derive theoretically and is often assumed to be equal to the phase velocity of the primary waves (∼V e0 cos θ , cosine law), which has been supported to some extent by numerical simulations (e.g. Keskinen et al, 1979).…”

Section: Introductionmentioning

confidence: 99%

A first comparison of irregularity and ion drift velocity measurements in the E-region

et al. 2006

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Abstract. E-region irregularity velocity measurements at large flow angles with the STARE Finland coherent VHF radar are considered in context of the ion and electron velocity data provided by the EISCAT tristatic radar system, CUTLASS Finland coherent HF radar, and IMAGE fluxgate magnetometers. The data have been collected during a special experiment on 27 March 2004 during which EISCAT was scanning between several E-and one F-region altitudes along the magnetic field line. Within the E-region, the EISCAT measurements at two altitudes of 110 and 115 km are considered while the electron velocity is inferred from the EISCAT ion velocity measurements at 278 km. The lineof-sight (l-o-s) VHF velocity measured by STARE V VHF los is compared to the ion and electron velocity components (V i0 comp and V e0 comp ) along the STARE l-o-s direction. The comparison with V e0 comp for the entire event shows that the measurements exhibit large scatter and small positive correlation. The correlation with V e0 comp was substantial in the first half of the interval under study when V e0 comp was larger in magnitude. The comparison with V i0 comp at 110 and 115 km shows a considerable positive correlation, with VHF velocity being typically larger (smaller) in magnitude than V i0 comp at 110 km (115 km) so that V VHF los appears to be bounded by the ion velocity components at two altitudes. It is also demonstrated that the difference between V VHF los and V i0 comp at 110 km can be treated, in the first approximation, as a linear function of the effective backscatter height h eff also counted from 110 km; h eff varies in the range 108-114 km due to the altitude integration effects in the scattering cross-section. Our results are consistent with the notion that Correspondence to: R. A. Makarevich (r.makarevich@latrobe.edu.au) VHF velocity at large flow angles is directly related to the ion drift velocity component at an altitude h eff .

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“…This, incidentally, must also imply that gradients could be instrumental in determining the observed speed by affecting threshold conditions (Farley & Fejer, 1975;St.-Maurice et al, 1994). Type II waves have likewise been associated with linearly stable waves excited by turbulence through a mode-coupling process (Keskinen et al, 1979;Sudan, 1983). As such they would have a Doppler shift consistent with the mean line-of-sight component of the electron drift, at least above 100 km altitude (more on this below).…”

Section: Introductionmentioning

confidence: 99%

The influence of non-isothermal electrons and neutral wind structures on the doppler properties of vertical m-size field-aligned irregularities in the low latitude E-region

St.-Maurice¹,

Choudhary²

2007

Rev. Bras. Geof.

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ABSTRACT.Meter size irregularities are routinely studied with radars in the equatorial and low latitude regions. In both instances echoes from the E-region (90 to 120 km altitude) are a common occurrence. The resulting echoes are labeled as so-called Type I or Type II according to their spectral signature. In this paper we show that the phase velocity of Type I echoes increases with decreasing altitude owing to thermal feedback effects taking place in the growth process. We also show that Type II echoes can be influenced by atmospheric neutral winds to the point of revealing the presence of Kelvin-Helmholtz billows, as shown by a recently studied example taken from the Gadanki radar in India.Keywords: equatorial electrojet, plasma waves and instabilities, ionospheric irregularities, low latitude E-region, VHF radar spectra, quasi-periodic echoes, KelvinHelmholtz billows, turbulence.RESUMO. Irregularidades com escala de metros são estudadas rotineiramente com radares nas regiões de baixas latitudes e equatoriais. Em ambos os estudosé comum a ocorrência de ecos da região E (90 a 120 km de altitude). Os ecos resultantes são denominados de Tipo I e Tipo II de acordo com sua assinatura espectral. Neste trabalho nós mostramos que a velocidade de fase dos ecos tipo I aumentaà medida que diminui a altitude devido a efeitos térmicos causados pela própria irregularidade durante seu processo de desenvolvimento. Nós também mostramos que os ecos do Tipo II podem ser influenciados pelos ventos neutros atmosféricos ao ponto de revelar a presença de ondas do tipo Kelvin-Helmholtz, conforme demonstrado em alguns exemplos de estudos recentes realizados com o radar Gadanki naÍndia.Palavras-chave: eletrojato equatorial, ondas de plasma e instabilidades, irregularidades ionosféricas, região E em baixas latitudes, espectros obtidos com radares em VHF, ecos quase-periódicos, ondas do tipo Kelvin-Helmholtz, turbulência.

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Temporal and spatial power spectrum studies of numerical simulations of Type II gradient drift irregularities in the equatorial electrojet

Cited by 103 publications

References 31 publications

Unified theory of Type I and Type II irregularities in the equatorial electrojet

Unified theory of Type I and Type II irregularities in the equatorial electrojet

A first comparison of irregularity and ion drift velocity measurements in the E-region

The influence of non-isothermal electrons and neutral wind structures on the doppler properties of vertical m-size field-aligned irregularities in the low latitude E-region

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