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Using the Arecibo 430 MHz incoherent scatter radar located in Puerto Rico, we report the characteristics of the smallest meteors observed by any ground-based instruments. Coupled with an efficient pulse coding technique, the radar detects over 40 meteors per minute in the dawn hours. The typical mass of these meteors is estimated to be 10-13 kg and the corresponding radius is about 2 m. The velocity of the meteors is concentrated within a narrow range at a given time from midnight to noon. Numerical simulations show that such a characteristic is most consistent with meteoroids having circular orbits in inclined planes. The orbital evolution of these meteoroids are most significantly affected by Poynting-Robertson and solar wind drags. They are captured by the Earth on their way to spiral into the Sun. At the mass range where drag forces dominate, Earth-crossing meteoroids are mostly expected to be in quasi-circular orbits because they can be produced anywhere outside the Earth’s orbit. Our observation demonstrates this is indeed the case for retrograde meteoroids.
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Sporadic micro-meteoroid source radiant distribution inferred from the Arecibo 430 MHz radar observations
ABSTRACT This work presents the result of sporadic meteor radiant density distribution using the Arecibo 430 MHz incoherent scatter radar (ISR) located in Puerto Rico for the first time. Although numerous meteor studies have been carried out using the Arecibo ISR, meteoroid radiant density distribution has remained a mystery as the Arecibo radar cannot measure vector velocity. A numerical orbital simulation algorithm using dynamic programming and stochastic gradient descent is designed to solve the sporadic meteoroid radiant density and the corresponding speed distributions of the meteors observed at Arecibo. The data set for the algorithm comprises over 250 000 meteors from Arecibo observations between 2009 and 2017. Five of the six recognized sporadic meteor sources can be identified from our result. There is no clearly identifiable South Apex source. Instead, there is a broad distribution between +/−30° ecliptic latitude, with the peak density located in the North Apex direction. Our results also indicate that the Arecibo radar is not sensitive to meteors travelling straight into or perpendicular to the antenna beam but is most sensitive to meteors with an arrival angle between 30° and 60°. Our analysis indicates that about 75 per cent of meteoroids observed by the Arecibo radar travel in prograde orbits when the impact probability is considered. Most of the retrograde meteoroids travel in inclined low-eccentricity orbits.
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- PAR ID:
- 10389012
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 515
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 2088 to 2098
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/mnras/stac1921
