Radar observation of kinetic effects at meter scales for Farley‐Buneman plasma waves

Haldoupis, C.; Schlegel, K.; Hussey, G. C.; Koehler, J. A.

doi:10.1029/2001ja009193

Cited by 4 publications

(5 citation statements)

References 41 publications

(73 reference statements)

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“…On the other hand, there are only about 10% of the observed values which correspond to (L N ) ⊥ <3−5 km for which the ratio V 1.1 m /V 3.1 m is expected to be affected by the gradient drift term, in accord with the FB-GD linear instability theory. It is important to stress that for the overall mean irregularity velocity ratio of 1.09, the theoretical predictions suggest that this mean value corresponds to gradient-free Farley-Buneman waves, as concluded by Balsley and Farley (1971) and Haldoupis et al (2002).…”

Section: Comparison With Theorymentioning

confidence: 99%

“…A detailed analysis of the observed type 1 echo properties at 144-and 50-MHz observations was carried out by Haldoupis et al (2002). During the two months of observations, more than 20 events of type 1 echoes were identified, with lifetimes ranging between 30 s to a few minutes, and then their mean and peak Doppler velocities were estimated carefully from 10-second power spectra.…”

Section: -Mhz To 50-mhz Type 1 Velocity Ratiosmentioning

confidence: 99%

“…In their study, Haldoupis et al (2002) used a linear kinetic model of the Farley-Buneman instability to show that the overall 9% difference in the type 1 velocities at 144-and 50-MHz could be explained only by kinetic effects. The same conclusion was also reached by Balsley and Farley (1971) who used the predictions of Farley's (1963) kinetic theory.…”

Section: Comparison With Theorymentioning

confidence: 99%

“…The present paper makes an effort to address this question by testing a key prediction of the linear theory, namely that a destabilizing (stabilizing) plasma gradient reduces (increases) the instability threshold, and thus the type 1 wave phase velocities at threshold, more at longer than at shorter wavelengths. To investigate this point we rely here on the observations of Haldoupis et al (2002), obtained from a rare backscatter experiment of simultaneous type 1 echoes at two widely spaced VHF frequencies, 144 MHz and 50 MHz. The measurements were made from the island of Crete and refer to backscatter from the mid-latitude E-region during conditions of destabilized sporadic E (E s ) plasma, when steep plasma density gradients are believed to be present.…”

Section: Introductionmentioning

confidence: 99%

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Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?

et al. 2005

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Abstract. The physics of the unstable E-region plasma is based on the modified two stream, or Farley-Buneman, and the gradient drift instabilities. The theory combines both mechanisms into a single dispersion relation which applies for the directly generated short-scale plasma waves, known as type 1 irregularities. In the absence of a plasma gradient it is only the two stream mechanism acting which favors wave excitation if E×B electron drifts relative to the ions exceed a threshold slightly above the ion acoustic speed. On the other hand, the theory also predicts that a destabilizing (stabilizing) electron density gradient acts to decrease (increase) the ion acoustic threshold, and hence the wave phase velocities at threshold, depending on the gradient strength and the wavelength. Given a destabilizing plasma gradient, the threshold reduction is larger at longer than shorter wavelengths and thus the best way to test the gradient role is by simultaneous observations of type 1 waves at two or more radio backscatter frequencies. The present paper relies on dual frequency backscatter observations of 1.1 m and 3.1 m type 1 irregularities made simultaneously at 144 MHz and 50 MHz, respectively, in mid-latitude sporadic E-layers. Using as typical plasma gradient scale lengths for destabilized sporadic E-layers those that are obtained from rocket electron density profiles, the radar observations are compared with the predictions of kinetic theory. The results suggest that the plasma density gradient effect on meter scale Farley-Buneman waves is not important. This is reinforced further by the analysis of backscatter from destabilized meteor trail plasma when very steep gradients are expected in electron density. The present findings, and more from past studies, question the electron density gradient role in the generation of short-scale plasma waves as predicted by the linear instability theory. This deserves attention and more study.

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Section: Comparison With Theorymentioning

confidence: 99%

Section: -Mhz To 50-mhz Type 1 Velocity Ratiosmentioning

confidence: 99%

Section: Comparison With Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?

et al. 2005

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“…There fore, the higher phase ve loc ity of twostream waves is ex cited at a new thresh old ve loc ity larger than the nom i nal ion acous tic ve loc ity. Ad di tion ally, large phase ve loc ity two-stream waves were sel dom ob served by ra dar in re gions be sides the equa to rial and the auroral re gion (e.g., Schlegel and Haldoupis 1994;Huang and Chu 1998;Haldoupis et al 2002). Voiculescu and Ignat (2005) showed the oret i cally that par al lel wind hin ders the gen er a tion of waves and anti-par al lel wind re duces sig nif i cantly the elec tric field strength re quired for ex cit ing waves.…”

Section: Introductionmentioning

confidence: 99%

Simulations of Wind Field Effect on Two-Stream Waves in the Equatorial Electrojet

Fern¹,

Kuo²

2009

Terr. Atmos. Ocean. Sci.

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AB STRACTThe wind field ef fect on the phase ve loc i ties of 3-to 10-me ter Farley-Buneman two-stream waves in the equa to rial E re gion ion o sphere at al ti tudes in the range of 95 -110 km is stud ied by nu mer i cal sim u la tion. The be hav ior of this two-stream wave in the uni form wind field U n in a plane per pen dic u lar to the Earth's mag netic field is sim u lated with a two-di men sional two-fluid code in which elec tron in er tia is ne glected while ion in er tia is re tained. It is con firmed that, the thresh old con di tion for the ap pear ance of two-stream waves is V C U D th s nand the phase ve loc ity of the two-stream wave at the thresh old con di tion is V p » C s + U n cos q, where q is the el e va tion an gle of the wave prop a ga tion in a lim ited range andThe first for mula in di cates that the wind field par al lel (anti-par al lel) to the elec tron drift ve loc ity will raise (lower) the thresh old drift ve loc ity by the amount of the wind speed. This means that par al lel wind is a sta ble fac tor, while anti-par al lel wind is an un sta ble fac tor of two-stream waves. This may ex plain why high speed (larger than acous tic speed) two-stream waves were rarely ob served, since larger thresh old drift ve loc ity de mands larger po lar iza tion elec tric field. The re sult of the sim u la tions at the sat u ra tion stage show that when V D was only slightly larger than V D th , the hor i zon tal phase ve loc ity of the two-stream wave would grad u ally down-shift to the thresh old phase ve loc ity C s + U n . The physical implications of which are discussed. . A three-dimen sional nu mer i cal model cal cu la tion (Hysell et al. 2002) in di cated that large hor i zon tal neu tral winds have strong effects on the equa to rial elec tro-jet and low lat i tude ion ospheric cur rent sys tem. These re ports sug gest that rou tine neu tral wind mea sure ments are re quired to ad vance the research of the ef fects of neu tral wind on the equa to rial electro-jet, and a proper for mula of wind ef fects is needed. Balsley et al. (1976) at tempted to es ti mate wind ve loc ities from mea sur ing the phase ve loc i ties of type 1/type 2 waves in the elec tro-jet. They as sumed in their mea sure ments that the phase ve loc ity of type 1 waves (two stream waves) in the frame of ref er ence of ions was the ion acous tic ve loc ity; hence, the Dopp ler ve loc ity ob served by ra dar on the ground would be (1) where r V p is the wave phase ve loc ity; r U n is the neu tral wind ve loc ity; and r k is the ra dar wave vec tor. Broche et al. (1978) also de rived the phase ve loc i ties of type 1 and type 2 ir reg u lar i ties to il lus trate the role of neu tral winds, and obtained the same Eq. (1) at the thresh old con di tion. Hanuise and Cro chet (1981) ap plied Eq. (1) to re duce the phase veloc i ties of 5 -50-m wave length type 1 waves from their radar ob ser va tion data, and found that the phase ve loc ity of short scale waves (l @ 5 m) was near the nom i nal ion acoustic ve loc ity (around 3...

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Ion thermal and dispersion effects in Farley-Buneman instabilities

et al. 2015

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Farley-Buneman modes are an example of the collisional instability, which is thought to be the dominant mechanism for the irregularities in low ionosphere region. Despite high collisionality due to electron-neutral and ion-neutral collisions, the kinetic effects associated with finite temperature are important for determination of the mode frequencies and growth rate. This is especially important for ion component that is largely unmagnetized due to low ion cyclotron frequency. The ion thermal effects are strongly pronounced for shorter wavelengths and are crucial for the growth rate cut-off at high wavenumbers. We develop an extended fluid model for ion dynamics to incorporate the effects of ion thermal motion. The model is based on the extended MHD model that includes the evolution equations for higher order moments such as ion viscosity and ion heat flux. We also develop the generalized Chapman-Enskog closure model that provides exact linear closures based on the linearized kinetic equation. The results of these models are compared and tested against the linear kinetic model. The dispersion of Farley-Buneman modes and growth rate behavior are investigated in the short wavelength region.

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Radar observation of kinetic effects at meter scales for Farley‐Buneman plasma waves

Cited by 4 publications

References 41 publications

Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?

Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?

Simulations of Wind Field Effect on Two-Stream Waves in the Equatorial Electrojet

Ion thermal and dispersion effects in Farley-Buneman instabilities

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