Interplanetary dust particles of micron-size probably associated with the Leonid meteor stream

Alexander, W. M.; Mccracken, C. W.; LaGow, H. E.

doi:10.1029/jz066i011p03970

Cited by 17 publications

(10 citation statements)

References 2 publications

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“…Impact rates and fluxes for intervals of less than 80 days are, for lack of complete restoration of the data, computed on the basis of the 6307 impacts listed in the processed data, which had been corrected for the false counts caused by monitored interrogations of the magnetometer. The data presented here are based on the best available processed data from Vanguard 3 and, as such, supersede the data presented in earlier papers (Alexander and LaGow, 1960;Alexander, McCracken, and LaGow, 1961). A more detailed discussion of the time variations is therefore possible.…”

Section: Time Variationsmentioning

confidence: 77%

Meteor orbits and dust; the proceedings of a symposium

Hawkins¹

1967

Smithsonian Contributions to Astrophysics

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The Proceedings of the Symposium on Meteor Orbit* and Dust is published simultaneously as a NASA Special Publication (SP-135) and as Volume 11 of the Smithsonian Contributions to Astrophysics. This single publication thus serves in a dual capacity to satisfy the requirements of both agencies for the published record of this international meeting.The NASA Special Publications series, begun in 1962, makes available information derived from or of value to NASA activities, and includes such publications as conference proceedings, monographs, data compilations, handbooks, Bourcebooks, and special bibliographies.The IntroductionWe recently completed a general analysis of the atmospheric trajectories of 413 precisely reduced Super-Schmidt photographic meteors (Jacchia, Verniani, and Briggs, 1965). We studied the dependence of heights, lengths, decelerations, and magnitudes on such basic parameters as velocity, angle of incidence, and mass, as well as on derived parameters such as the ablation coefficient and the fragmentation index; the latter were in turn related to the other geometrical and physical characteristics, including the phenomena of wake and terminal blending. The results of the analysis are mainly concerned with physical characteristics of meteors; in this paper we shall limit ourselves to only a few points related to problems of orbits and distribution, namely, physical differences dependent on the type of orbit, peculiarities of individual showers, and the mass scale for photographic meteors.Systematic differences between groups of meteors Systematic differences in some physical characteristics between meteors in short-period and long-period orbits were first pointed out by Jacchia (1958Jacchia ( , 1963. He found that the beginning heights of meteors with aphelion distances greater than 7 a.u. were higher than the corresponding heights of meteors with aphelion distances smaller than 7 a.u. All meteors were, of course, reduced to the same brightness.• Smithsonian Astrophysical Observatory and Harvard College Observatory, Cambridge, Massachusetts.'Smithsonian Astrophysical Observatory and Harvard College Observatory; on leave from Centra Nationals per la Fisica dell'Atmosfera c la Meteorologia del C.N.R., Rome, Italy. * Smithsonian Astrophysical Observatory, Cambridge, Massachusetts.The present general analysis has confirmed the effect found by Jacchia: meteors with aphelion distance smaller than 6 a.u. appear 1.8 km lower than meteors in long-period orbits, reduced to the same velocity, mass, and zenith angle. The maximum light and end heights are correspondingly lower ( fig. 1). This effect is related to the different densities that we find for the two groups: on the average, meteors in short-period orbits appear to be about 1.4 times as dense as meteors in long-period orbits. In addition, for short-period meteors, the density increases as the aphelion distance decreases ( fig. 2). These systematic differences in density could be ascribed to the different conditions in which the meteoroids were formed ...

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Section: Time Variationsmentioning

confidence: 77%

Meteor orbits and dust; the proceedings of a symposium

Hawkins¹

1967

Smithsonian Contributions to Astrophysics

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“…Sounding rockets have also been used to derive estimates of meteoroid¯uxes in the Earth's upper atmosphere. Berg and Meredith [34], for example, reported a large number of impacts during an Aerobe NIL-25¯ight on November 17, 1955 (a point not missed by Alexander et al [32]). But again, no enhanced activity was recorded for the Leonid stream in that year and we are obliged to dismiss the result as spurious.…”

Section: Meteoroid Streamðsatellite Interactionsmentioning

confidence: 99%

“…The key question, of course, is can we believe it. There are several critical reasons why, given our advantage of hindsight, we should not believe the analysis of Alexander et al [32]. Firstly, caution must be directed towards the observations because the Vanguard III detector was an acoustic one and hence susceptible to unquali®ed noise from thermal variations.…”

Section: Meteoroid Streamðsatellite Interactionsmentioning

confidence: 99%

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Satellite impact probabilities: annual showers and the 1965 and 1966 Leonid storms

Beech

Jehn

Brown³

et al. 1999

Acta Astronautica

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AbstractÐThe stream meteoroid impact probability for space platforms is reviewed and found to be very low under normal circumstances. While the literature contains numerous accounts of spacecraft apparently su ering damage and/or interference during meteoroid stream encounters, we ®nd that there is, in fact, very little evidence to support such claims. This conclusion may not be valid, however, during meteor storms, when the¯ux of visual meteors can increase by factors in excess of 10 3 to 10 4 of that from the sporadic background. Special attention is directed towards the Leonid meteor storms of 1965 and 1966Ðthe only meteor storms since the dawn of the space age. The space platform impact probabilities during the 1966 storm were small but none negligible, being of order 1% for an exposed surface area of 2 m 2 at a limiting meteoroid mass of 10 À7 g (and assuming a stream mass index s = 2.0). The circumstances surrounding the possible encounters of the Pegasus II and III, and Mariner 4 spacecraft with Leonid stream meteoroids are discussed in some detail. While the 1966 Leonid meteor storm is the strongest on record (in the sense of the highest visual meteor rates) no apparent meteoroid in¯icted damage to a spacecraft can be unambiguously linked to it. This result is mostly a consequence of the small number and small size of spacecraft in Earth-orbit at the time of the 1966 storm. #

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“…Reports on swarms associated with periodic comets and/or meteor showers appear to be conflicting (Alexander et al 1961, Dubin et al 1963, McCracken et al 1967, Silverberg and Poultney 1969, Silverberg 1970, Alexander and Bohn 1974, Hoffmann et al 1975a, 1975b. THE ZODIACAL CLOUD Whipple (1967) suggests that comets are probably also a major, if not the sole, source of dust that keeps the self-destructive zodiacal cloud in a steady-state condition, and that Periodic Comet Encke might have been the most significant contributor to the cloud in the past.…”

Section: Meteor Streamsmentioning

confidence: 99%