Characteristics of Radio Echoes from Meteor Trails: III The Behaviour of the Electron Trails after Formation

Greenhow, J. S.

doi:10.1088/0370-1301/65/3/301

Cited by 52 publications

(15 citation statements)

References 8 publications

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“…In the troposphere, the order of magnitude of w is known roughly to have the value (1) from the work of Brunt [i8]. At the meteoric level, •vhich will be taken as 90 kin, a value will be deduced •or w by fitting the formulas of sections 2 and 3 to visual observations of meteortrails made by Liller and Whipple [9], and to radio observations of meteor-trails made by Greenhow [8,34]. This comparison between turbulence-theory and meteoric observations is made in section 4.…”

mentioning

confidence: 99%

Turbulence in the ionosphere with applications to meteor-trails, radio-star scintillation, auroral radar echoes, and other phenomena

Booker¹

1956

J. Geophys. Res.

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The irregularities in electron‐density responsible for incoherent scattering of radio waves in the ionosphere are discussed on the assumption of isotropic turbulence in the neutral molecules, with allowance made for the effect of the earth's magnetic field on the associated irregularities in the density of the charges particles. The atmospheric model used is based on rocket observations, extrapolated upwards in height where necessary. Tentative formulas are deduced for the large eddies based on a non‐standard application of the Richardson number. For the small eddies, the standard formulas of turbulence‐theory are used. These formulas all depend on a quantity w, which is the rate of supply of turbulence‐energy to the large eddies and also the rate of removal of turbulence‐energy from the small eddies, measured per unit mass of atmosphere. The value of w at the meteoric level (90 km) is found to be around 25 watts/kg by comparison between the theory and meteoric observations (both visual and radio). By the same technique, a more tentative value of 1,000 watts/kg is deduced for the level responsible for scintillation of radio stars, although a lower value is probably appropriate when scintillation is weak. These values of w in the ionosphere are high compared with Brunt's value of 5×10−4 watt/kg for the troposphere. It is shown, however, that these high values of w in the ionosphere are quite possible and even reasonable. It is deduced that the time of onset of irregular fading of meteoric echoes in the VHF band is more likely to be due to roughness of the trail caused by the small eddies than to gross distortion of the trail caused by the large eddies. It follows that, after about a second, VHF radar echoes from a meteor‐trail must be calculated using a theory based on incoherent scattering, thereby questioning the theory of Kaiser and Closs [37] as an explanation of long‐duration meteor‐echoes. It is also shown that radio‐star scintillation cannot be explained in terms of turbulence at a level of 400 km, but that reasonable results can be obtained if the level is reduced to 200–300 km. Among other applications considered is the possibility of radio communication via incoherent scattering in the F region of the atmosphere. The conditions under which such communication should be sought are described in section 11.

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confidence: 99%

Turbulence in the ionosphere with applications to meteor-trails, radio-star scintillation, auroral radar echoes, and other phenomena

Booker¹

1956

J. Geophys. Res.

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“…Long-enduring meteor trails behave as totally reflecting cylinders, and the echoes obtained from such trails show a slow rise in amplitude to a flat maximum and a final rapid exponential decay. Most echoes of this type have durations >> 0.3 s at h = 8.27 m [Greenhow, 1952], and they can not be completely…”

Section: Discussionmentioning

confidence: 99%

“…defines the duration to 1 divided by the exponent of the initial amplitude. Greenhow [1950Greenhow [ , 1952 studied in detail the behavior of ionized meteor trails after formation and showed that the dissipation of the ionization is primarily due to the diffusion process. He showed that the diffusion coefficient D and height h could be empirically related by the following equation:…”

Section: Introductionmentioning

confidence: 99%

Echo duration and diffusion coefficient measurements using meteor wind radar

Devara¹,

Ahmed²,

Rao³

1981

Radio Science

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The Meteor Wind Radar at Waltair (17°43′N, 83°18′E), India, was operated during June–July 1979 to study the echo durations and diffusion coefficients of underdense meteor trails. These measurements have also been used to evaluate the elevation angles of the specular reflection points. The most probable echo duration and elevation angle for the present system are found to be 60 ms and 23°, respectively. The values of measured diffusion coefficients (log10 D) are found to vary between 4.6 and 5.5 cm2 s−1. The diurnal variation of the diffusion coefficient showed a broad maximum during morning hours and a broad minimum during evening hours. The results are compared with the measurements at other stations.

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“…Returning to the issue of trail lifetime, Greenhow (1952) introduced the follow expression to determine the lifetime:…”

Section: Appendix C: Spatial and Temporal Scales Associated With Traimentioning

confidence: 99%

Decay times of transitionally dense specularly reflecting meteor trails and potential chemical impact on trail lifetimes

et al. 2016

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Abstract. Studies of transitionally dense meteor trails using radars which employ specularly reflecting interferometric techniques are used to show that measurable hightemperature chemistry exists at timescales of a few tenths of a second after the formation of these trails. This is a process which is distinct from the ambient-temperature chemistry that is already known to exist at timescales of tens of seconds and longer in long-lived trails. As a consequence, these transitionally dense trails have smaller lifetimes than might be expected if diffusion were the only mechanism for reducing the mean trail electron density. The process has been studied with four SKiYMET radars at latitudes varying from 10 to 75 • N, over a period of more than 10 years, 24 h per day. In this paper we present the best parameters to use to represent this behaviour and demonstrate the characteristics of the temporal and latitudinal variability in these parameters. The seasonal, day-night and latitudinal variations correlate reasonably closely with the corresponding variations of ozone in the upper mesosphere. Possible reasons for these effects are discussed, but further investigations of any causative relation are still the subject of ongoing studies.

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Characteristics of Radio Echoes from Meteor Trails: III The Behaviour of the Electron Trails after Formation

Cited by 52 publications

References 8 publications

Turbulence in the ionosphere with applications to meteor-trails, radio-star scintillation, auroral radar echoes, and other phenomena

Turbulence in the ionosphere with applications to meteor-trails, radio-star scintillation, auroral radar echoes, and other phenomena

Echo duration and diffusion coefficient measurements using meteor wind radar

Decay times of transitionally dense specularly reflecting meteor trails and potential chemical impact on trail lifetimes

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