共查询到20条相似文献，搜索用时 46 毫秒
1.
Computerized spherical harmonic analysis is applied to the morphology of the southern auroral oval. Records from 23 All Sky Camera stations together with visual observation reports for the period 1957–1959 constitute the raw data set. The mode of the derived auroral occurrence distribution function F(Kp, θ, φ) is regarded as the maximum probability contour and yields a set of auroral ovals. These 10 contours, one for each Kp level, are expressed in the invariant magnetic co-ordinates of Bond (1968). 相似文献
2.
S. R. Bourne 《Celestial Mechanics and Dynamical Astronomy》1972,6(2):167-186
This paper describes a method for finding literal expressions for the first order terms in the Moon's co-ordinates. The method is based on the use of rectangular co-ordinates and was originally proposed by Euler. The variation curve and the terms dependent on the first power of the Lunar eccentricity have been obtained. These results are compared with those of Hill and a number of errors in Hill's results have been found. 相似文献
3.
C. B. Watts' charts of the marginal zone of the Moon have been put into the form of tables of rectangular co-ordinates of points along the contours. These co-ordinates were recorded automatically on paper tape and transferred, firstly to a magnetic tape, then secondly to an exchangeable-disc cartridge allowing random access to every chart. 相似文献
4.
J. F. Palacián 《Celestial Mechanics and Dynamical Astronomy》2007,98(4):219-249
We study the dynamics of a satellite (artificial or natural) orbiting an Earth-like planet at low altitude from an analytical
point of view. The perturbation considered takes into account the gravity attraction of the planet and in particular it is
caused by its inhomogeneous potential. We begin by truncating the equations of motion at second order, that is, incorporating
the zonal and the tesseral harmonics up to order two. The system is formulated as an autonomous Hamiltonian and has three
degrees of freedom. After three successive Lie transformations, the system is normalised with respect to two angular co-ordinates
up to order five in a suitable small parameter given by the quotient between the angular velocity of the planet and the mean
motion of the satellite. Our treatment is free of power expansions of the eccentricity and of truncated Fourier series in
the anomalies. Once these transformations are performed, the truncated Hamiltonian defines a system of one degree of freedom
which is rewritten as a function of two variables which generate a phase space which takes into account all of the symmetries
of the problem. Next an analysis of the system is achieved obtaining up to six relative equilibria and three types of bifurcations.
The connection with the original system is established concluding the existence of various families of invariant 3-tori of
it, as well as quasiperiodic and periodic trajectories. This is achieved by using KAM theory techniques. 相似文献
5.
Diarmuid O'Mathuna 《Celestial Mechanics and Dynamical Astronomy》1970,1(3-4):467-478
For Vinti's dynamical problem, there is proposed a new form of solution wherein all three coordinates are expressed in terms of one independent variable. The formulae for the three co-ordinates are clear generalizations of the corresponding formulae for the Kepler problem while the independent variable corresponds to the true anomaly. The solution is completed by the relation connecting the independent variable with time: the latter is a generalization of the well known Kepler time-angle relationship. From the form and method of solution the main qualitative features of the motion are readily derived. 相似文献
6.
This paper considers the possibility of using pulsed and continuous wave radio sources to scatter or reflect a signal from the ionisation produced by an Extensive Air Shower (EAS) to provide a precise indication of the source co-ordinates of the primary gamma ray. It indicates the limits of such methods and suggests a route which may result in a significant improvement in the current precision of cosmic gamma ray source coordinates. 相似文献
7.
We investigate the orbital diffusion and the stickiness effects in the phase space of a 3-dimensional volume preserving mapping.
We first briefly review the main results about the stickiness effects in 2-dimensional mappings. Then we extend this study
to the 3-dimensional case, studying for the first time the behavior of orbits wandering in the 3-dimensional phase space and
analyzing the role played by the hyperbolic invariant sets during the diffusion process. Our numerical results show that an
orbit initially close to a set of invariant tori stays for very long times around the hyperbolic invariant sets near the tori.
Orbits starting from the vicinity of invariant tori or from hyperbolic invariant sets have the same diffusion rule. These
results indicate that the hyperbolic invariant sets play an essential role in the stickiness effects. The volume of phase
space surrounded by an invariant torus and its variation with respect to the perturbation parameter influences the stickiness
effects as well as the development of the hyperbolic invariant sets. Our calculations show that this volume decreases exponentially
with the perturbation parameter and that it shrinks down with the period very fast. 相似文献
8.
J. Hpfner 《Astronomische Nachrichten》1980,301(1):27-32
The old programme of observations (cf. Beobachtungsergebnisse 1964 and Astronomische Zeit- und Breitenbestimmungen 1965, 1) was modified. The conditions described in Instruction (1956) were used again. As previously (cf. Beobachtungsergebnisse 1964), the stars were selected in respect of the derivation of corrections to the co-ordinates of the stars. The new programme, which has been in use since September of 1978, can be used up to the year 2000. 相似文献
9.
Recently we (Roy and Rana, 1990a) critically examined the self-consistency of the EIH equations of motion. A static spherically symmetric body as was pointed out there may not appear as a point mass with all its mass concentrated at its centre to a particle placed outside the body. An attempt to analyse this aspect further is made here in the context of the Chandrasekhar gauge. A comparison is also made with the general solutions obtained by Schwarzschild in the standard co-ordinates. Certain difficulties still exist. 相似文献
10.
In FRW space time Brans-Dicke theory is developed for two cases: (i) the vacuum and (ii) the perfect fluid model. The field equations are transformed into a much simpler form under a change of time co-ordinates and then the solutions are determined for the above cases. An equation of statep =/3 (radiation) is assumed in the case of perfect fluid. 相似文献
11.
This paper describes the discovery of families of multiple invariant shape solutions for collinear three-craft Coulomb formations
with set charges, as well as the results of linear stability analysis on such formations. The charged spacecraft are assumed
to be spinning about each other in deep space without relevant gravitational forces present. Up to three invariant shape solutions
are possible for a single set of craft charges. This behavior, only speculated in previous work, is confirmed through analysis
and numerical simulation examples. In fact, distinct regions are analytically described where two or three invariant shape
solutions exist for a single charge set. These regions are analyzed to determine what range of trajectories are possible.
Linear stability analysis for circular trajectories yields the first examples of marginally stable three-craft invariant shape
formations. Linearly stable behavior is only observed when two invariant shape solutions result for one set of charges, where
one shape will be unstable and the other marginally stable. Numerical simulation illustrates stability for ten orbital periods
when perturbations are confined to the orbital plane. When out of plane motion is considered the shapes are found to be weakly
unstable, though the out of plane motion appears to be decoupled from in plane motion to first order. 相似文献
12.
Due to the existence of invariant tori, chaotic sea and hyperbolic structures in higher dimensional phase space of a volume-preserving
map, the diffusion route of chaotic orbits will be complicated. The velocity of diffusion will be very slow if the orbits
are near an invariant torus. In order to realize this complicated diffusion phenomenon, in this paper we study the diffusion
characters in the different regions, i.e., chaotic, hyperbolic and invariant tori's regions. We find that for the three different
regions, the diffusion velocities are different. The diffusion velocity in the vicinity of an invariant torus is the slowest
one.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
The Machinga meteorite fell in the Southern Province of Malawi on January 22, 1981, at approximately 1000 hours local time. The fall site is about 7.5 km SW of Machinga and has the co-ordinates 15° 12′44″ S., 35°14′32″ E. A single crusted mass weighing 93.2 kg was recovered. The Machinga meteorite is an L6 chondrite with olivine Fa24.5 and orthopyroxene Fs21.1. The silicates have a granular texture and the stone has been shocked. 相似文献
14.
Hawking’s radiation effect of Klein-Gordon scalar field, Dirac particles and Maxwell’s electromagnetic field in the non-stationary
rotating de Sitter cosmological space-time is investigated by using a method of generalized tortoise co-ordinates transformation.
The locations and the temperatures of the cosmological horizons of the non-stationary rotating de Sitter model are derived.
It is found that the locations and the temperatures of the rotating cosmological model depend not only on the time but also
on the angle. The stress-energy regularization techniques are applied to the two dimensional analog of the de Sitter metrics
and the calculated stress-energy tensor contains the thermal radiation effect. 相似文献
15.
A method for space mission trajectory design is presented in the form of a greedy global search algorithm. It uses invariant manifolds of unstable periodic orbits and its main advantage is that it performs a global search for the suitable legs of the invariant manifolds to be connected for a preliminary transfer design, as well as the appropriate points of the legs for maneuver application. The designed indirect algorithm bases the greedy choice on the optimality conditions that are assumed for the theoretical minimum transfer cost of a spacecraft when using invariant manifolds. The method is applied to a test case space mission design project in the Earth–Moon system and is found to compare favorably with previous techniques applied to the same project. 相似文献
16.
Brian L. Smith 《Astrophysics and Space Science》1976,43(2):411-424
It was shown in a previous paper, Smith (1975), that the determination of the structure of rotating polytropes by expansion in the small rotational parameter constitutes asingular perturbation problem as arises also, for example, in large Reynolds' number approximations in fluid dynamics. The technique used by him — the method of matched asymptotic expansions — is, in fact, just an extension of the Prandtl boundary layer theory familiar in this latter context. In this paper — the first of two — we introduce an alternative procedure: the method of strained co-ordinates; and for comparison purposes again consider rotating polytropes. In Paper II we extend this approach to differentially rotating stars and present an illustrative example. 相似文献
17.
On closed but non-geometrically similar orbits 总被引：1，自引：1，他引：0
As is well known, the existence of geometrically similar orbits for a particle moving under a central conservative force is a consequence of the fact that the corresponding potential energy is a homogeneous function of the co-ordinates. In this paper, we consider a particular non-homogeneous potential of the form V = U + W, where U and W are homogenous functions of degrees −1 and −2, respectively, because, for this potential, the search of closed orbits, for discrete values of the angular momentum, is straightforward. We focus our attention on these daisy-like charming orbits and graphically show the consequences of the impossibility of geometrical similarity. 相似文献
18.
19.
Mercè Ollé Joan R. Pacha Jordi Villanueva 《Celestial Mechanics and Dynamical Astronomy》2004,90(1-2):87-107
The paper deals with different kinds of invariant motions (periodic orbits, 2D and 3D invariant tori and invariant manifolds of periodic orbits) in order to analyze the Hamiltonian direct Hopf bifurcation that
takes place close to the Lyapunov vertical family of periodic orbits of the triangular equilibrium point L4 in the 3D restricted three-body problem (RTBP) for the mass parameter, μ greater than (and close to) μR (Routh’s mass parameter). Consequences of such bifurcation, concerning the confinement of the motion close to the hyperbolic
orbits and the 3D nearby tori are also described. 相似文献
20.
J. Henrard 《Celestial Mechanics and Dynamical Astronomy》1982,27(1):3-22
The theory of the adiabatic invariant predicts the long term evolution of mechanical systems with slowly varying parameters.Unfortunately, it is not valid when the system goes across a critical trajectory. This case is important because it can lead to capture into resonance.Analysing the motion in the vincinity of the critical trajectory, we are able to give general formulae for the probability of capture and to show that in general, the adiabatic invariant is conserved (allowance being made for the geometrical discontinuity in its definition at the critical orbit). 相似文献