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1.
The dynamical evolution of meteoroid streams associated with cornets Encke, Halley, Machholz 1986 VIII and asteroid Phaethon is discussed. It is shown that the planetary perturbations can greatly increase the streams thickness and each stream may produce several couples of meteor showers active in different seasons of the year. The theoretical and observed data are in a satisfactory accordance. 相似文献
2.
Fragmentation of an ablating meteoroid is a process that depends on the physical constitution of the body and the internal
structure. These parameters are thought to control temperature gradients within the body. Phase signatures from the University
of Canterbury’s AMOR facility are shown to be able to resolve instances in which meteors are subject to gross macro-fragmentation
where the meteoroid body disrupts into a few discrete components. 相似文献
3.
L.A. Rogers 《Planetary and Space Science》2005,53(13):1341-1354
Conventional meteoroid theory assumes that the dominant mode of ablation (which we will refer to as thermal ablation) is by evaporation following intense heating during atmospheric flight. Light production results from excitation of ablated meteoroid atoms following collisions with atmospheric constituents. In this paper, we consider the question of whether sputtering may provide an alternative disintegration process of some importance. For meteoroids in the mass range from 10-3 to and covering a meteor velocity range from 11 to , we numerically modeled both thermal ablation and sputtering ablation during atmospheric flight. We considered three meteoroid models believed to be representative of asteroidal ( mass density), cometary () and porous cometary () meteoroid structures. Atmospheric profiles which considered the molecular compositions at different heights were use in the sputtering calculations. We find that while in many cases (particularly at low velocities and for relatively large meteoroid masses) sputtering contributes only a small amount of mass loss during atmospheric flight, in some cases sputtering is very important. For example, a porous meteoroid at will lose nearly 51% of its mass by sputtering, while a asteroidal meteoroid at will lose nearly 83% of its mass by sputtering. We argue that sputtering may explain the light production observed at very great heights in some Leonid meteors. We discuss methods to observationally test the predictions of these computations. A search for early gradual tails on meteor light curves prior to the commencement of intense thermal ablation possibly represents the most promising approach. The impact of this work will be most dramatic for very small meteoroids such as those observed with large aperture radars. The heights of ablation and decelerations observed using these systems may provide evidence for the importance of sputtering. 相似文献
4.
Peter Jenniskens 《Earth, Moon, and Planets》2008,102(1-4):505-520
The history of associating meteor showers with asteroidal-looking objects is long, dating to before the 1983 discovery that
3200 Phaethon moves among the Geminids. Only since the more recent recognition that 2003 EH1 moves among the Quadrantids are
we certain that dormant comets are associated with meteoroid streams. Since that time, many orphan streams have found parent
bodies among the newly discovered Near Earth Objects. The seven established associations pertain mostly to showers in eccentric
or highly inclined orbits. At least 35 other objects are tentatively linked to streams in less inclined orbits that are more
difficult to distinguish from those of asteroids. There is mounting evidence that the streams originated from discrete breakup
events, rather than long episodes of gradual water vapor outgassing. If all these associations can be confirmed, they represent
a significant fraction of all dormant comets that are in near-Earth orbits, suggesting that dormant comets break at least
as frequently as the lifetime of the streams. I find that most pertain to NEOs that have not yet fully decoupled from Jupiter.
The picture that is emerging is one of rapid disintegration of comets after being captured by Jupiter, and consequently, that
objects such as 3200 Phaethon most likely originated from among the most primitive asteroids in the main belt, instead. They
too decay mostly by disintegration into comet fragments and meteoroid streams. The disintegration of dormant comets is likely
the main source of our meteor showers and the main supply of dust to the zodiacal cloud.
Editorial handling: Frans Rietmeijer. 相似文献
5.
Gerhard Drolshagen Valeri Dikarev Markus Landgraf Holger Krag Wim Kuiper 《Earth, Moon, and Planets》2008,102(1-4):191-197
Over the last decade several new models for the sporadic interplanetary meteoroid flux have been developed. These include
the Divine-Staubach and the Dikarev model. They typically cover mass ranges from 10−18 g to 1 g and are applicable for model specific Sun distance ranges between 0.1 AU and 20 AU Near 1 AU averaged fluxes (over
direction and velocities) for all these models are tuned to the well established interplanetary model by Grün et al. However,
in many respects these models differ considerably. Examples are the velocity and directional distributions and the assumed
meteoroid sources. In this paper flux predictions by the various models to Earth orbiting spacecraft are compared. Main differences
are presented and analysed. The persisting differences even for near Earth space can be seen as surprising in view of the
numerous ground based (optical and radar) and in situ (captured Inter Stellar Dust Particles, in situ detectors and analysis
of retrieved hardware) measurements and simulations. 相似文献
6.
Peter Jenniskens 《Earth, Moon, and Planets》2008,102(1-4):5-9
The International Astronomical Union at its 2006 General Assembly in Prague has adopted a set of rules for meteor shower nomenclature,
a working list with designated names (with IAU numbers and three-letter codes), and established a Task Group for Meteor Shower Nomenclature in Commission 22 (Meteors and Interplanetary Dust) to help define which meteor showers exist from well defined groups of
meteoroids from a single parent body. 相似文献
7.
The orbital evolution of the two meteorites Příbram and Neuschwanstein on almost identical orbits and also several thousand
clones were studied in the framework of the N-body problem for 5,000 years into the past. The meteorites moved on very similar
orbits during the whole investigated interval. We have also searched for photographic meteors and asteroids moving on similar
orbits. There were five meteors found in the IAU MDC database and six NEAs with currently similar orbits to Příbram and Neuschwanstein.
However, only one meteor 161E1 and one asteroid 2002 QG46 had a similar orbital evolution over the last 2,000 years. 相似文献
8.
Josep M. Trigo-Rodriguez José M. Madiedo Peter S. Gural Alberto J. Castro-Tirado Jordi Llorca Juan Fabregat Standa Vítek Pep Pujols 《Earth, Moon, and Planets》2008,102(1-4):231-240
By using high-resolution, low-scan-rate, all-sky CCD cameras, the SPanish Meteor Network (SPMN) is currently monitoring meteor
and fireball activity on a year round basis. Here are presented just a sampling of the accurate trajectory, radiant and orbital
data obtained for meteors imaged simultaneously from two SPMN stations during the continuous 2006–2007 coverage of meteor
and fireball monitoring. Typical astrometric uncertainty is 1–2 arc min, while velocity determination errors are of the order
of 0.1–0.5 km/s, which is dependent on the distance of each event to the station and its particular viewing geometry. The
cameras have demonstrated excellent performance for detecting meteor outbursts. The recent development of automatic detection
software is also providing real-time information on the global meteor activity. Finally, some examples of the all-sky CCD
cameras applications for detecting unexpected meteor activity are given. 相似文献
9.
M. Hajduková Jr. 《Earth, Moon, and Planets》2008,102(1-4):67-71
The hyperbolic meteor orbits among the 4,581 photographic and 62,906 radar meteors of the IAU MDC have been analysed using
statistical methods. It was shown that the vast majority of hyperbolic orbits has been caused by the dispersion of determined
velocities. The large proportion of hyperbolic orbits among the known meteor showers strongly suggests the hyperbolicity of
the meteors is not real. The number of apparent hyperbolic orbits increases inversely proportional to the difference between
the mean heliocentric velocity of meteor shower and the parabolic velocity limit. The number of hyperbolic meteors in the
investigated catalogues does not, in any case, represent the number of interstellar meteors in observational data. The apparent
hyperbolicity of these orbits is caused by a high spread in velocity determination, shifting a part of the data through the
parabolic limit. 相似文献
10.
In this initial study, we propose a new distance function D
V
involving heliocentric vectorial orbital elements. The function measures differences between: the orbital energies, the angular
momentums vectors and the Laplace vectors. In comparison with the widely used D
SH
criterion of Southworth and Hawkins, D
D
criterion of Drummond and their hybrid D
H
by Jopek, the new function contains one invariant with respect to the principal secular perturbation: the orbital energy.
The new function proved to be useful in the classification amongst the IAU2003 meteoroids which we searched for streams by
D
V
function and also using D
SH
and D
N
-function given by Valsecchi et al. For major streams, the results agree very well. For minor, and near-ecliptical streams
the results sometimes differ markedly. 相似文献