Determining meteoroid bulk densities using a plasma scattering model with high-power large-aperture radar data

Close, Sigrid; Volz, Ryan; Loveland, Rohan; Macdonell, Alex; Colestock, P.; Linscott, I. R.; Oppenheim, M. M.

doi:10.1016/j.icarus.2012.07.033

Cited by 21 publications

(17 citation statements)

References 40 publications

(47 reference statements)

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“…It can be seen from this figure that the ensemble of electrons model is in reasonably good agreement with the FDTD simulations for the range of masses between 0.01 and 1000 micrograms, where at low velocities the RCS from the FDTD simulations is at most a factor of 0.1 smaller than that resulting from the coherent scattering approach. The FDTD model assumes a Gaussian electron density distribution (Close et al 2012), and from these results it appears that coherent scattering works reasonably well as an approximation when the HE is underdense, that is, the peak plasma frequency (w p,max ) is lower than the radar frequency (w p = f 2 0 0 ). For this case, the head plasma should emulate coherent scattering as the radar wave is able to penetrate the plasma and be seen by all of the head plasma electrons, which each scatter the radar wave independently and coherently.…”

Section: Size Of Meteor Hementioning

confidence: 86%

Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

Janches

Swarnalingam

Carrillo‐Sánchez

et al. 2017

ApJ

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We present a path forward on a long-standing issue concerning the flux of small and slow meteoroids, which are believed to be the dominant portion of the incoming meteoric mass flux into the Earth's atmosphere. Such a flux, which is predicted by dynamical dust models of the Zodiacal Cloud, is not evident in ground-based radar observations. For decades this was attributed to the fact that the radars used for meteor observations lack the sensitivity to detect this population, due to the small amount of ionization produced by slow-velocity meteors. Such a hypothesis has been challenged by the introduction of meteor head echo (HE) observations with High Power and Large Aperture radars, in particular the Arecibo 430 MHz radar. Janches et al. developed a probabilistic approach to estimate the detectability of meteors by these radars and initially showed that, with the current knowledge of ablation and ionization, such particles should dominate the detected rates by one to two orders of magnitude compared to the actual observations. In this paper, we include results in our model from recently published laboratory measurements, which showed that (1) the ablation of Na is less intense covering a wider altitude range; and (2) the ionization probability, b ip , for Na atoms in the air is up to two orders of magnitude smaller for low speeds than originally believed. By applying these results and using a somewhat smaller size of the HE radar target we offer a solution that reconciles these observations with model predictions.

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Section: Size Of Meteor Hementioning

confidence: 86%

Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

Janches

Swarnalingam

Carrillo‐Sánchez

et al. 2017

ApJ

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“…However, routine operational worldwide head echo observations utilizing HPLA radar only began in earnest almost three decades later [ Pellinen‐Wannberg and Wannberg , ; Mathews et al , ; Close et al , ; Sato et al , ; Chau and Woodman , ; Janches et al , ; Sparks et al , ]. Because head echoes allow direct detection of the meteoroid flight in the atmosphere, they provide information about meteoroid changes during the actual entry process and so provide key information for understanding mass loss mechanisms [ Kero et al , ; Janches et al , ], electromagnetic plasma processes [ Dyrud et al , ], as well as enabling the quantification of the mass range of detected particles [ Close et al , ] and their effect in the upper atmosphere [ Fentzke and Janches , ; Gardner et al , ]. HPLA radars are characterized by their high peak transmitter power (≥1 MW) at VHF and UHF frequencies that range between 50 and 1200 MHz, and antenna apertures, in the form of arrays or dishes, that have areas ranging between ∼800 and 9 ×10 4 m 2 [ Janches et al , ] (see also section 5 and Table ).…”

Section: Introductionmentioning

confidence: 99%

Interferometric meteor head echo observations using the Southern Argentina Agile Meteor Radar

et al. 2014

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A radar meteor echo is the radar scattering signature from the free electrons generated by the entry of extraterrestrial particles into the atmosphere. Three categories of scattering mechanisms exist: specular, nonspecular trails, and head echoes. Generally, there are two types of radars utilized to detect meteors. Traditional VHF all‐sky meteor radars primarily detect the specular trails, while high‐power, large‐aperture (HPLA) radars efficiently detect meteor head echoes and, in some cases, nonspecular trails. The fact that head echo measurements can be performed only with HPLA radars limits these studies in several ways. HPLA radars are sensitive instruments constraining the studies to the lower masses, and these observations cannot be performed continuously because they take place at national observatories with limited allocated observing time. These drawbacks can be addressed by developing head echo observing techniques with modified all‐sky meteor radars. Such systems would also permit simultaneous detection of all different scattering mechanisms using the same instrument, rather than requiring assorted different classes of radars, which can help clarify observed differences between the different methodologies. In this study, we demonstrate that such concurrent observations are now possible, enabled by the enhanced design of the Southern Argentina Agile Meteor Radar (SAAMER). The results presented here are derived from observations performed over a period of 12 days in August 2011 and include meteoroid dynamical parameter distributions, radiants, and estimated masses. Overall, the SAAMER's head echo detections appear to be produced by larger particles than those which have been studied thus far using this technique.

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“…We scale the measurements relative to the median since it is less sensitive to outliers, especially since masses and bulk densities vary across 2 orders of magnitude between meteoroids. Based upon previous ALTAIR measurements, their respective median values are approximately m = 1.36 × 10 −5 g and

ρ_{m} = 0.45 \frac{g}{c m^{3}}

[ Close et al , , ]. The resulting estimated densities are shown in Figures and .…”

Section: Resultsmentioning

confidence: 99%

“…The use of radars to collect meteor data has been well established since the late 1940s [Hey et al, 1946], but the HPLA radars have yielded significant insights into the field of meteor physics [Pellinen-Wannberg and Wannberg, 1994;Janches et al, 2000;Close et al, 2000;Mathews et al, 2001;Oppenheim et al, 2008]. In particular, because of their ability to directly observe the velocity and deceleration of the head echo target, the masses and bulk densities of meteoroids can be derived [Close et al, 2005[Close et al, , 2012. Since atmospheric density is a major component to these calculations, meteoroids have been used as probes for atmospheric science before the advent of in situ monitoring [Opik, 1958].…”

Section: Meteoroids and Radar Datamentioning

confidence: 99%

Neutral density estimation derived from meteoroid measurements using high‐power, large‐aperture radar

2016

JGR Atmospheres

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We present a new method to estimate the neutral density of the lower thermosphere/upper mesosphere given deceleration measurements from meteoroids as they enter Earth's atmosphere. By tracking the plasma (referred to as head echoes) surrounding the ablating meteoroid, we are able to measure the range and velocity of the meteoroid in 3‐D. This is accomplished at Advanced Research Projects Agency Long‐Range Tracking and Instrumentation Radar (ALTAIR) with the use of four additional receiving horns. Combined with the momentum and ablation equations, we can feed large quantities of data into a minimization function which estimates the associated constants related to the ablation process and, more importantly, the density ratios between successive layers of the atmosphere. Furthermore, if we take statistics of the masses and bulk densities of the meteoroids, we can calculate the neutral densities and its associated error by the ratio distribution on the minimum error statistic. A standard deviation of approximately 10% can be achieved, neglecting measurement error from the radar. Errors in velocity and deceleration compound this uncertainty, which in the best case amounts to an additional 4% error. The accuracy can be further improved if we take increasing amounts of measurements, limited only by the quality of the ranging measurements and the probability of knowing the median of the distribution. Data analyzed consist mainly of approximately 500 meteoroids over a span of 20 min on two separate days. The results are compared to the existing atmospheric model NRLMSISE‐00, which predicts lower density ratios and static neutral densities at these altitudes.

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Determining meteoroid bulk densities using a plasma scattering model with high-power large-aperture radar data

Cited by 21 publications

References 40 publications

Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

Interferometric meteor head echo observations using the Southern Argentina Agile Meteor Radar

Neutral density estimation derived from meteoroid measurements using high‐power, large‐aperture radar

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