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41.
The cometary meteoroid ejection model of Jones and Brown [Physics, Chemistry, and Dynamics of Interplanetary Dust, ASP Conference Series
104 (1996b) 137] was used to simulate ejection from comets 55P/Tempel-Tuttle during the last 12 revolutions, and the last 9 apparitions
of 109P/Swift-Tuttle. Using cometary ephemerides generated by the Jet Propulsion Laboratory’s (JPL) HORIZONS Solar System
Data and Ephemeris Computation Service, two independent ejection schemes were simulated. In the first case, ejection was simulated
in 1 h time steps along the comet’s orbit while it was within 2.5 AU of the Sun. In the second case, ejection was simulated
to occur at the hour the comet reached perihelion. A 4th order variable step-size Runge–Kutta integrator was then used to
integrate meteoroid position and velocity forward in time, accounting for the effects of radiation pressure, Poynting–Robertson
drag, and the gravitational forces of the planets, which were computed using JPL’s DE406 planetary ephemerides. An impact
parameter (IP) was computed for each particle approaching the Earth to create a flux profile, and the results compared to
observations of the 1998 and 1999 Leonid showers, and the 1993 and 2004 Perseids. 相似文献
42.
43.
I. P. Williams 《Celestial Mechanics and Dynamical Astronomy》2001,81(1-2):103-113
Meteors are streaks of light seen in the upper atmosphere when particles from the inter-planetary dust complex collide with the Earth. Meteor showers originate from the impact of a coherent stream of such dust particles, generally assumed to have been recently ejected from a parent comet. The parent comets of these dust particles, or meteoroids, fortunately, for us tend not to collide with the Earth. Hence there has been orbital changes from one to the other so as to cause a relative movement of the nodes of the meteor orbits and that of the comet, implying changes in the energy and/or angular momentum. In this review, we will discuss these changes and their causes and through this place limits on the ejection process. Other forces also come into play in the longer term, for example perturbations from the planets, and the effects of radiation pressure and Poynting–Robertson drag. The effect of these will also be discussed with a view to understanding both the observed evolution in some meteor streams. Finally we will consider the final fate of meteor streams as contributors to the interplanetary dust complex. 相似文献
44.
Chin Array is a dense portable broadband seismic network to cover the entire continental China, and the Phase I is deployed along the north-south seismic belt in southwest China. In this study, we analyze seismic data recorded on the Chin Array following the February 15,2013 Chelyabinsk(Russia) meteor. This was the largest known object entering the Earth's atmosphere since the1908 Tunguska meteor. The seismic energy radiated from this event was recorded by seismic stations worldwide including the dense Chin Array that are more than 4000 km away. The weak signal from the meteor event was contaminated by a magnitude 5.8 Tonga earthquake occurred *20 min earlier. To test the feasibility of detecting the weak seismic signals from the meteor event, we compute vespagram and perform F-K analysis to the surface-wave data. We identify a seismic phase with back azimuth(BAZ) of 329.7° and slowness of 34.73 s/deg, corresponding to the surface wave from the Russian meteor event(BAZ *325.97°). The surface magnitude(MS) of the meteor event is 3.94 ± 0.18. We also perform similar analysis on the data from the broadband array F-net in Japan, and find the BAZ of the surface waves to be316.61°. With the different BAZs of Chin Array and F-net,we locate the Russian meteor event at 58.80°N, 58.72°E.The relatively large mislocation(*438 km as compared with 55.15°N, 61.41°E by others) may be a result of thebending propagation path of surface waves, which deviates from the great circle path. Our results suggest that the dense Chin Array and its subarrays could be used to detect weak signals at teleseismic distances. 相似文献
45.
A central depository for meteor orbits obtained by photographic techniques, as a part of the IAU Meteor Data Center, was moved
to the Astronomical Institute of the Slovak Academy of Sciences in Bratislava in 2001. The current version of the catalogue
contains data on 4581 meteor orbits obtained by 17 different stations or groups from the period 1936 to 1996. Since 1996 a
few huge campaigns were organised including very successful Leonids and Perseids. That is why we would prepare a new more
complete version of the database. The main aim of this paper is a call to the observers of meteors having new or recalculated/remeasured
data on photographic meteors to send them to the MDC, where after a check and consultations with the observer, the orbits
will be included in the database. 相似文献
46.
J. Tóth L. Kornoš Š. Gajdoš D. Kalmančok P. Zigo J. Világi M. Hajduková Jr. 《Earth, Moon, and Planets》2008,102(1-4):257-261
We present our experience and initial results of single-station observation using the new fish-eye TV system, as well as double
station TV observation of the Geminids 2006 shower. The fixed fish-eye TV system was developed for monitoring meteor activity
throughout the year. We discuss the astrometric precision of our observations using the UFOAnalyser software. 相似文献
47.
The Lyrid Meteor Stream: Orbit and Structure 总被引:1,自引:0,他引:1
A filamentary structure in the Lyrid meteor stream based on photographic orbits available in the IAU Meteor database is identified
and studied. About 17 Lyrids are found in the database and the stream mean orbit is derived. The shower radiant is compact,
of a size 2° × 1.5°. Applying a stricter limiting value for the Southworth-Hawkins D-criterion, two distinct filaments in
the stream, on a short and a long period orbit, are separated. To confirm their consistency as filaments, their orbital evolution
over 5,000 years is investigated. 相似文献
48.
The correlation of sporadic meteor rates from radar observations in January, August, and December non-show-er periods in 1958–2000,
and relevant solar activity represented by the solar relative number, R, is investigated. Similar analysis of the December
sporadic period was already presented by Simek 1999, and Pecina. Complete analysis indicates high correlation of both phenomena
with sporadic meteor counts curve following that of solar activity after 1.5–2 years in the mean eleven year solar cycle with
the correlation index exceeding 70%. This result supports the large volume of observing material of the Ondřejov meteor radar
in the above mentioned span covering almost four solar cycles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their
dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies
ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection'ages provide an opportunity to study
space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous
thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous
solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The
occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates,
collections of surviving dust becomea comet nucleus-sampling mission.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
50.
Radio meteor observations by Ham-band beacon or FM radio broadcasts using “Ham-band Radio meteor Observation Fast Fourier
Transform” (HROFFT) an automatic operating software have been performed widely in recent days. Previously, counting of meteor
echoes on the spectrograms of radio meteor observation was performed manually by observers. In the present paper, we introduce
an automatic meteor echo counting software application. Although output images of the HROFFT contain both the features of
meteor echoes and those of various types of noises, a newly developed image processing technique has been applied, resulting
in software that enables a useful auto-counting tool. There exists a slight error in the processing on spectrograms when the
observation site is affected by many disturbing noises. Nevertheless, comparison between software and manual counting revealed
an agreement of almost 90%. Therefore, we can easily obtain a dataset of detection time, duration time, signal strength, and
Doppler shift of each meteor echo from the HROFFT spectrograms. Using this software, statistical analyses of meteor activities
is based on the results obtained at many Ham-band Radio meteor Observation (HRO) sites throughout the world, resulting in
a very useful “standard” for monitoring meteor stream activities in real time. 相似文献