<i>Physics of Meteor Flight in the Atmosphere</i>

Öpik, E.; Singer, S. Fred

doi:10.1063/1.3060580

Cited by 75 publications

(102 citation statements)

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“…Then the energy flux on the meteor surface due to air molecule collisions is pr 2 rv 3 /2, where r and v are the meteor radius and velocity, and r is the local air density. Consistent with other authors [e.g., Pecina and Ceplecha, 1983;Opik, 1958;Bronshten, 1983;Ceplecha et al, 1998] we will write the meteor mass loss rate as…”

Section: Discussionsupporting

confidence: 59%

Analysis of ALTAIR 1998 meteor radar data

Zinn

Colestock

et al. 2011

J. Geophys. Res.

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[1] We describe a new analysis of a set of 32 UHF meteor radar traces recorded with the 422 MHz Advanced Research Project Agency Long-Range Tracking and Identification Radar facility in November 1998. Emphasis is on the absolute velocity measurements and inferences that can be drawn from them regarding the meteoroid masses and mass densities. We find that the 3-D velocity versus altitude data can be fitted as quadratic functions of the path integrals of the atmospheric densities versus distance, and deceleration rates derived from those fits all show the expected behavior of increasing with decreasing altitude. We also describe a computer model of the coupled processes of collisional heating, radiative cooling, evaporative cooling and ablation, and deceleration for meteoroids composed of defined mixtures of mineral constituents. For each of the cases in the data set, we ran the model starting with the measured initial velocity and trajectory inclination and with various trial values of the quantity mr s 2 (initial mass times mass density squared) and then compared the computed deceleration versus altitude curves versus the measured ones. In this way we arrived at the best fit values of the mr s 2 for each of the measured traces. Then further, assuming various trial values of the density r s , we compared the computed mass versus altitude curves with similar curves for the same set of meteoroids determined previously from the measured radar cross sections and an electrostatic scattering model. In this way we arrived at estimates of the best fit mass densities r s for each of the cases.

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Section: Discussionsupporting

confidence: 59%

Analysis of ALTAIR 1998 meteor radar data

Zinn

Colestock

et al. 2011

J. Geophys. Res.

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“…This temperature depends on the vapor pressure law and is in the range 1300-2000 K for silicates (Opik 1958) and 180-220 K for ices (Iseli et al 2002).…”

Section: Appendix B: Planetesimal Mass Deposition: Planetesimal Compomentioning

confidence: 99%

Grain opacity and the bulk composition of extrasolar planets

Mordasini

2014

A&A

114

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Context. We investigate the grain opacity κ gr in the atmosphere (outer radiative zone) of forming planets. This is important for the observed planetary mass-radius relationship since κ gr affects the primordial H/He envelope mass of low-mass planets and the critical core mass of giant planets. Aims. The goal of this study is to derive a simple analytical model for κ gr and to explore its implications for the atmospheric structure and resulting gas accretion rate. Methods. Our model is based on the comparison of the timescales of the most important microphysical processes. We consider grain settling in the Stokes and Epstein drag regime, growth by Brownian motion coagulation and differential settling, grain evaporation in hot layers, and grain advection due to the contraction of the envelope. With these timescales and the assumption of a radially constant grain flux, we derive the typical grain size, abundance, and opacity. Results. We find that the dominating growth process is differential settling. In this regime, κ gr has a simple functional form; it is given as 27Q/8Hρ in the Epstein regime in the outer atmosphere and as 2Q/Hρ for Stokes drag in the deeper layers. Grain growth leads to a typical radial structure of κ gr with high ISM-like values in the outer layers but a strong decrease towards the deeper parts where κ gr becomes so low that the grain-free molecular opacities take over. Conclusions. In agreement with earlier results, we find that κ gr is typically much lower than in the ISM. In retrospect, this suggests that classical giant planet formation models should have considered the grain-free case to be as equally meaningful as the full ISM opacity case. The equations also show that a higher dust input in the top layers does not strongly increase κ gr . This has two important implications. First, for the formation of giant planet cores via pebbles, there could be the adverse effect that pebbles tend to increase the grain input high in the atmosphere because of ablation. This could in principle increase the opacity, making giant planet formation difficult. Our study indicates that this potentially adverse effect is not important. Second, it means that a higher stellar [Fe/H] which presumably leads to a higher surface density of planetesimals only favors giant planet formation without being detrimental to it because of an increased κ gr . This corroborates the result that core accretion can explain the observed increase of the giant planet frequency with stellar [Fe/H].

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“…In the first stage, meteors ablate as a result of high velocity collisions with atmospheric molecules (Öpik, 1958;McKinley, 1961;McNeil et al, 1998;McNiel et al, 2002;Vondrak et al, 2008). An initial important development is the formation of a heated dense sphere of gas around the meteoroid, referred to as a vapour cloud (e.g.…”

Section: Characteristics Of Strong and Transitionally Dense Meteor Trmentioning

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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Physics of Meteor Flight in the Atmosphere

Cited by 75 publications

References 0 publications

Analysis of ALTAIR 1998 meteor radar data

Analysis of ALTAIR 1998 meteor radar data

Grain opacity and the bulk composition of extrasolar planets

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

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