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1.
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
2.
Werner Singer Ralph Latteck Luis Federico Millan Nick J. Mitchell Jens Fiedler 《Earth, Moon, and Planets》2008,102(1-4):403-409
Many meteoroids burn up between about 120 km and 70 km, deposit metals and dust and form ionized trails which are detected
by radars. Model studies about the influence of neutral or positively charged background dust on the ambipolar diffusion indicate
that significant smaller decay times should be observed for weak meteor echoes compared to strong meteor echoes which can
affect the estimation of temperatures. The variation of meteor decay times in dependence on echo strength, height, and season
was studied using radar observations at 69° N, 22° S, and 67° S. Significantly reduced decay times were found for weak echoes
below about 88 km at low latitudes throughout the year, and at high latitudes with the exception of summer. In summer at high
latitudes, decreasing decay times of weak and strong meteors are observed at altitudes below about 85 km during the appearance
of noctilucent clouds. The impact of reduced decay times on the estimation of neutral temperatures from decay times is discussed. 相似文献
3.
We report results from two station, short-baseline (< 100 m) high resolution measurements of faint meteors (limiting meteor
magnitude +9) with the goal of measuring their optical trail widths. Meteors were observed using two 0.40 m Newtonian telescopes
(field of view ˜0.4 degrees) equipped with image intensifiers. Both telescopes were vertically oriented in a fixed mount and
pointed to the same field of view. One system used a gated image intensified camera allowing the transverse velocity component
to be measured. The widest trail captured, out of a total of 34 common events measured by both optical systems, had a full-width
to half-maximum of 1.37±0.71 m. The widest trail overall was captured by the gated system only, and was found to have a full-width
of ∼
∼10 m. The brightness variation across this trail was found to be best represented by a Lorentzian. Most trails were smaller
than our resolution limit and hence we could only place upper limits on their optical width. These were generally less than
1 m after correction for instrumental effects. Four meteors were found to have heights near 65 km and very low transverse
velocities. These may be indicative of a largely unreported high density asteroidal component at these faint meteor magnitudes. 相似文献
4.
The recent development and data collection results of the Astrobiology Instrumentation for Meteor Imaging and Tracking (AIM-IT)
system, has demonstrated an ability to point narrow field-of-view instruments at transient events such as meteors. AIM-IT
uses the principle of tracking moving objects via a paired set of relay mirrors along with an integrated hardware/software
solution, to acquire and track meteors in real-time. Development of the instrument has progressed from a prototype rocker-box
system through more recent use of a fast response mirror system during several meteor shower campaigns. Several narrow field
of view instruments have been deployed using AIM-IT including high spatial resolution video, high frame rate video, and meteor
spectrographic equipment. Analysis of the imagery shows evidence for meteor fragmentation in as many as 20% of the meteors
tracked thus far. The success of the AIM-IT technology in tracking meteors during their luminous flight provides a new tool
in enhancing the capabilities and data volume that can be obtained with existing narrow field of view instruments. 相似文献
5.
Efforts to link minor meteor showers to their parent bodies have been hampered both by the lack of high-accuracy orbits for
weak showers and the incompleteness of our sample of potential parent bodies. The Canadian Meteor Orbital Radar (CMOR) has
accumulated over one million meteor orbits. From this large data set, the existence of weak showers and the accuracy of the
mean orbits of these showers can be improved. The ever-growing catalogue of near-Earth asteroids (NEAs) provides the complimentary
data set for the linking procedure. By combining a detailed examination of the background of sporadic meteors near the orbit
in question (which the radar data makes possible) and by computing the statistical significance of any shower association
(which the improved NEA sample allows) any proposed shower–parent link can be tested much more thoroughly than in the past.
Additional evidence for the links is provided by a single-station meteor radar at the CMOR site which can be used to dispel
confusion between very weak showers and statistical fluctuations in the sporadic background. The use of these techniques and
data sets in concert will allow us to confidently link some weak streams to their parent bodies on a statistical basis, while
at the same time showing that previously identified minor showers have little or no activity and that some previously suggested
linkages may simply be chance alignments. 相似文献
6.
Sang-hyeon Ahn 《Earth, Moon, and Planets》2004,95(1-4):63-68
We have analyzed the meteor records in the chronicles of the east Asian countries, especially the Korean records. Our results
show that the seasonal variation of sporadic meteors has persisted at least for the last two millennia. We also observed the
prominent showers such as the Perseids and the Leonids, which are formed by Halley-type comets. We obtained the regression
rate of nodal points for the Leonids to be approximately 1.52± 0.04 days per century. 相似文献
7.
S. S. De B. K. De Pinaki Pal B. Bandyopadhyay S. Barui D. K. Haldar Suman Paul Minu Sanfui Goutami Chattopadhyay 《Astrophysics and Space Science》2011,332(2):353-357
The detection of 2009 Leonid, Perseid and Geminid meteor showers over Agartala, Tripura, India (Lat: 23.0° N, Long: 91.4° E)
will be reported here by using two VLF receivers tuned to subionospheric transmitted VLF signals at the frequency 16.4 kHz
from Aldra Island, Norway (Lat: 66.42° N, Long: 13.13° E) and the other at 18.2 kHz from Vijayananarayanam, India (Lat: 8.4° N;
Long: 77.7° E). The received signals exhibited their peak values on November 17, 2009 when ZHR (Zenithal Hourly Rate) was
highest. Some typical variations which are observed in the records of amplitude during the 2009 Leonid, Perseid and Geminid
meteor showers will be presented in this paper. 相似文献
8.
Štefan Gajdoš 《Earth, Moon, and Planets》2008,102(1-4):117-123
A new meteroid stream—October Ursa Majorids—was announced by Japanese observers on Oct. 14–16, 2006 (Uehara et al. 2006).
Its weak manifestation was detected among coincidental major meteor showers (N/S Taurids, Orionids), as its meteors radiated
from a higher placed radiant on the northern sky. We have tried to find out previous displays of the stream throughout available
meteor orbits databases, and among ancient celestial phenomena records. Although we got no obvious identification, there are
some indications that it could be a meteor shower of cometary origin with weak/irregular activity, mostly overlayed by regular
coincidental meteor showers. With a procedure based on D-criterion (Southworth and Hawkins 1963) we found a few records in IAU MDC database of meteor photographic orbits which fulfill
common similarity limits, for October Ursae Majorids. However, their real association cannot be established, yet. With respect
to the mean orbit of this stream, we suggest for its parent body a long-period comet. 相似文献
9.
V. Sidorov S. Kalabanov S. Sidorova I. Filin T. Filimonova 《Earth, Moon, and Planets》2004,95(1-4):165-179
The discrete quasitomographic method of the analysis of the interferometric data of meteor radar gives us the possibility
of measuring coordinates and velocities of very weak meteor showers with a 2 × 2 square degree resolution on the celestial
sphere. The minimal rate of the meteors in each microstream is five meteors per day. At such sensitivity, basic distinctions
between irregularities of the sporadic background and meteor streams vanish. More than 1000 of the detected microshowers per
month are associated with a combination of (a) the large known meteor showers, (b) the weaker known meteor showers and (c)
till now unknown associations of microshowers. All microshowers regardless of association have the identical velocities, limited
areas of radiation and near simultaneity of their acting dates. The results are compiled as maps of radiant distribution and
average velocities of microstreams for different months. From these it is possible to see how the microshower activity for
various discrete sites on the celestial sphere correlate with the behavior of the well-known meteor streams and thus to infer
the orbital properties of the different microstream configurations. 相似文献
10.
We have carried out double-station TV meteor observations between 1990 and 1994. The orbits of 326 meteors have been determined from doubly observed meteors, and radiant distributions are studied. The mean magnitude of the observed meteors was as faint as +4.7, since I.I. (Image Intensifier) and Video cameras were used. Radiants were widely distributed over the celestial sphere. The velocity distribution showed some similarity with the distribution predicted by the theoretical radiant distribution from comets rather than that from asteroids. In all 13 showers including both major and minor meteor showers were detected from radiant distributions of the observed meteors; from the orbital elements and meteor velocities as well as from the radiant directions. 相似文献
11.
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
12.
S. S. De B. Bandyopadhyay S. Barui Suman Paul D. K. Haldar D. De B. K. De S. Chattopadhyay A. K. Kundu 《Earth, Moon, and Planets》2012,108(2):111-121
The effects of 2009 Leonid Meteor Shower upon the two VLF subionospheric transmitted signals and vertical electric potential
gradient from the ground surface have been studied from Kolkata (Lat: 22.56°N, Long: 88.5°E) on November 17, 2009. The received
signals showed their peak values when ZHR (Zenithal Hourly Rate) was highest. Some typical variations in the outcome of these measurements during the meteor showers
will be presented in this paper. 相似文献
13.
L. M. G. Poole 《Astrophysics and Space Science》1995,230(1-2):471-478
Recent meteor research in South Africa, arising largely from the development of forward and back scatter observing systems, is briefly reviewed. The main areas of investigation have been the use of single station radars to deduce meteor radiant structures, the study of upper atmospheric wind patterns, and research into the factors which influence the performance of meteor burst communication systems. 相似文献
14.
Shinsuke Abe Noboru Ebizuka Hideyuki Murayama Katsuhito Ohtsuka Satoru Sugimoto Masa-yuki Yamamoto Hajime Yano Jun-ichi Watanabe Jiří Borovička 《Earth, Moon, and Planets》2004,95(1-4):265-277
Spectra of persistent meteor trains were observed at wavelength between 300 and 930 nm. Two obtained train spectra during
the 1998 and 2001 Leonid meteor showers are reported here. During the 1998 Leonids, one train was detected by a photographic
camera with a spectrograph covering 370–640 nm region. On the other hand, during the 2001 Leonids, video observations were
carried out using image intensified cameras in ultraviolet (UV), visible and near infrared (near-IR) wavelengths. Temperatures
in persistent trains have been measured by atmospheric O2 A(0,1) band at the wavelength near 864.5 nm. From a video spectrum obtained just 7 s after parent fireball’s flare, a rotational
temperature of 250 K at altitude of 88.0±0.5 km was estimated. We can say that the cooling time scale of train strongly depends
on the initial mass of its fireball at least for Leonids. Based on cooling constant calculated from our results, we estimated
a temperature of ∼
∼130 K as a final exothermic temperature at early stage of persistent trains. 相似文献
15.
Sanjay Kumar S. Priyadarshi S. Gopi Krishna A. K. Singh 《Astrophysics and Space Science》2012,339(1):165-178
The paper is based on the ionospheric variations in terms of vertical total electron content (VTEC) for the low solar activity
period from May 2007 to April 2009 based on the analysis of dual frequency signals from the Global Positioning System (GPS)
satellites recorded at ground stations Varanasi (Geographic latitude 25°16′ N, Longitude 82°59′ E), situated near the equatorial
ionization anomaly crest and other two International GNSS Service (IGS) stations Hyderabad (Geographic latitude 17°20′ N,
longitude 78°30′ E) and Bangalore (Geographic latitude 12°58′ N, longitude 77°33′ E) in India. We describe the diurnal and
seasonal variations of total electron content (TEC), and the effects of a space weather related event i.e. a geomagnetic storm
on TEC. The mean diurnal variation during different seasons is brought out. It is found that TEC at all the three stations
is maximum during equinoctial months (March, April, September and October), and minimum during the winter months (November,
December, January and February), while obtaining intermediate values during summer months (May, June, July and August). TEC
shows a semi-annual variation. TEC variation during geomagnetic quiet as well as disturbed days of each month and hence for
each season from May 2007 to April 2008 at Varanasi is examined and is found to be more during disturbed period compared to
that in the quiet period. Monthly, seasonal and annual variability of GPS-TEC has been compared with those derived from International
Reference Ionosphere (IRI)-2007 with three different options of topside electron density, NeQuick, IRI01-corr and IRI 2001.
A good agreement is found between the GPS-TEC and IRI model TEC at all the three stations. 相似文献
16.
M. D. Campbell-Brown 《Earth, Moon, and Planets》2004,95(1-4):297-301
The Arietid meteor shower is one of the strongest of the year. The origin of this daytime shower is unknown; the orbit is
therefore of great interest, since an accurate orbit distribution is needed to integrate the shower backward in time to test
associations with comets or asteroids. The orbital parameters of the Arietid shower as a function of time, with errors, have
been generated using 415 radar orbits gathered at the CMOR facility in Tavistock, Canada. 相似文献
17.
PETER JENNISKENS 《Earth, Moon, and Planets》2004,95(1-4):723-732
The successful application of modern observing techniques for Leonid storm observations show that meteor (shower) detections will have a bright future if the field will pursue difficult but important questions. How to forecast a satellite threatening meteor storm? What happens to the organic matter in meteors and can this be an important source of prebiotic molecules? What range of variations in composition and morphology exists among cometary grains and what does this tell us about the origin of the solar system? What long-period comets approach Earth orbit and can meteoroid streams provide early warning for giant impacts? What are the sources of interstellar and interplanetary grains? Just to mention a few. To answer these questions will need new technologies and facilities, some of which are being developed for other use. This may include NASA’s Stratospheric Observatory For Infrared and sub-millimeter Astronomy (SOFIA). In addition, big-science space missions can drive the field if meteor detections are an integral part. Special events, such as meteor outbursts and the “artificial meteor” from the reentry of sample return capsules from interplanetary space, can mobilize observing and theoretical efforts. These and other future opportunities are briefly discussed. 相似文献
18.
Apostolos A. Christou 《Earth, Moon, and Planets》2004,95(1-4):425-431
Based on the number of planet-approaching cometary orbits at Mars and Venus relative to the Earth, there should be ample opportunities
for observing meteor activity at those two planets. The ratio of planet-approaching Jupiter family comets (JFCs) at Mars,
Earth, and Venus is 4:2:1 indicating that JFC-related outbursts would be more frequent at Mars than the Earth. The relative
numbers of planet-approaching Halley-type comets (HTCs) implies that the respective levels of annual meteor activity at those
three planets are similar. We identify several instances where near-comet outbursts (Jenniskens, P.: 1995, Astron. Astrophys. 295, 206–235) may occur. A possible double outburst of this type at Venus related to 45P/Honda-Mrkos-Padjusakova may be observable
by the ESA Venus Express spacecraft in the summer of 2006. Similarly, the Japanese Planet-C Venus orbiter may observe an outburst related to 27P/Crommelin’s perihelion passage in July 2011. Several additional opportunities
exist to observe such outbursts at Mars from 2019 to 2026 associated with comets 38P/Stephan-Oterma, 13P/Olbers and 114P/Wiseman-Skiff. 相似文献
19.
将作者在变质量天体力学所得理论结果应用于太阳质量损失对流星群轨道根数变化的长期效应上。太阳质量损失包括光子辐射和太阳风造成的质量损失。利用G—M型变质量天体轨道根数变化方程的一阶和二阶解对15个流星群轨道半长轴、近日点距离、轨道周期和近日点经度因太阳质量损失造成的每世纪的长期改变效应做了数值计算,并得出计算结果。其计算结果表明,太阳质量损失使流星群轨道半长轴每世纪的改变效应较明显,它们同太阳距离的扩大影响值得关注,但对轨道周期的拉长每世纪的影响甚小,对近日点经度只有量级变化小到可以略而不计。 相似文献
20.
Yue-hua Ma You-wen He Pin-xin Xu Hai-bin Zhao 《Chinese Astronomy and Astrophysics》2008,32(2):186-196
During the first international joint observation of the Leo strong meteor shower, multidisciplinary and multi-media synthetic observation of Leo and Draco strong meteor showers and their catastrophic space weather events were carried out. The comprehensive analysis of the observed and related data of the Leo, Perseus and Draco strong meteor showers obtained for near half a century (from 1957 to 2003) fully verifies that the non-sporadic periodic strong meteor shower may lead to catastrophic space weather events. Preliminary identification is made of the following: the mechanism of formation of strong meteor showers, the law of occurrence of the fbEs abnormal peak and serious safety hazards for astronavigation. Also discussed in this paper are the evolutionary process of cometary dust, the law of occurrence and loss of cosmic dust storm and the mechanism of maintaining cosmic dust in the mid-latitude Es layer. 相似文献