A comparison of detection sensitivity between ALTAIR and Arecibo meteor observations: Can high power and large aperture radars detect low velocity meteor head-echoes

Janches, Diego; Close, Sigrid; Fentzke, J. T.

doi:10.1016/j.icarus.2007.08.022

Cited by 51 publications

(63 citation statements)

References 25 publications

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“…Since faster meteors generally occur at higher altitudes, distributions measured by meteor radars are biased towards the lower speeds. In fact, Janches et al (2008) showed that HPLA radars observe the same population of meteors as observed by meteor radars, and in addition detect a population of faster meteors that ablate at altitudes where specular trails are not efficiently detected. However, the magnitude of the head echo still depends on the meteoroid mass and velocity, and each HPLA radar is sensitive to a particular mass range .…”

Section: Introductionmentioning

confidence: 92%

A chemical model of meteoric ablation

et al. 2008

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Abstract. Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca + in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. DiffusionCorrespondence to: J. M. C. Plane (j.m.c.plane@leeds.ac.uk) of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Nonthermal sputtering causes ∼35% mass loss from the fastest (∼60-70 km s −1 ) and smallest (10 −17 -10 −13 g) meteoroids, but makes a minor contribution to the overall ablation rate.

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Section: Introductionmentioning

confidence: 92%

A chemical model of meteoric ablation

et al. 2008

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“…In fact, it has already been shown (Hunt et al, 2004;Close et al, 2007) that a careful accounting for instrumental effects can diminish the discrepancy in the measured velocity distribution, though differences remain (Janches et al, 2008).…”

Section: Velocity Distributions Of Transverse Versus Radial Scatter Rmentioning

confidence: 99%

“…There have been discrepancies between the velocity distributions of meteors as measured by these two techniques that have caused some concern within the community. Though the issues involved are complex, a concise summary of the conflicting observations was made by Janches et al (2008).…”

Section: Velocity Distributions Of Transverse Versus Radial Scatter Rmentioning

confidence: 99%

A dynamical model of the sporadic meteoroid complex

Wiegert

Vaubaillon

Campbell-Brown

2009

Icarus

134

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“…This modeling effort offers the ability to estimate meteoroid and meteor parameters from HPLA radar head-echo observations which are needed for several studies such as, precisely estimating the meteoric flux into the upper atmosphere in this mass range (Mathews et al, 2001; ARTICLE IN PRESS Janches et al, 2006;, understanding the ablation and ionization processes and evolution characteristics of the meteor plasma (Janches and ReVelle, 2005;Dyrud et al, 2005Dyrud et al, , 2007c, and determination of the measurement biases of a particular radar as a function of various meteor parameters (Close et al, 2007;Janches et al, 2008). We also point out here that meteoroid fragmentation and its effects as observed using head echoes has gained recent interest (see Kero et al, 2008;Mathews et al, 2007).…”

mentioning

confidence: 99%