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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 DetectionWe 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, Beta 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.
Document ID
20180000543
Document Type
Reprint (Version printed in journal)
Authors
Janches, D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Swarnalingam, N. (Catholic Univ. of America Washington, DC, United States)
Carrillo-Sanchez, J. D. (Leeds Univ. United Kingdom)
Gomez-Martin, J. C. (Leeds Univ. United Kingdom)
Marshall, R. (Colorado Univ. Boulder, CO, United States)
Nesvorny, D. (Southwest Research Inst. Boulder, CO, United States)
Plane, J. M. C. (Leeds Univ. United Kingdom)
Feng, W. (Leeds Univ. United Kingdom)
Pokorny, P. (Catholic Univ. of America Washington, DC, United States)
Date Acquired
January 17, 2018
Publication Date
June 26, 2017
Publication Information
Publication: The Astrophysical Journal
Volume: 843
Issue: 1
ISSN: 0004-637X
Subject Category
Space Sciences (General)
Report/Patent Number
GSFC-E-DAA-TN50883
Funding Number(s)
CONTRACT_GRANT: NSF-AGS-1451241
CONTRACT_GRANT: NNG11PL10A
Distribution Limits
Public
Copyright
Other
Keywords
meteorites
meteors
meteoroids – zodiacal dus