共查询到20条相似文献，搜索用时 31 毫秒
1.
Kathrin A. Hochmuth Franz V. Feilitzsch Teresa Marrodán Undagoitia Lothar Oberauer Walter Potzel Michael Wurm Brian D. Fields 《Earth, Moon, and Planets》2006,99(1-4):253-264
A future large-volume liquid scintillator detector such as the proposed 50 kton LENA (Low Energy Neutrino Astronomy) detector
would provide a high-statistics measurement of terrestrial antineutrinos originating from β-decays of the uranium and thorium
chains. Additionally, the neutron is scattered in the forward direction in the detection reaction . Henceforth, we investigate to what extent LENA can distinguish between certain geophysical models on the basis of the angular
dependence of the geoneutrino flux. Our analysis is based on a Monte-Carlo simulation with different levels of light yield,
considering an unloaded PXE scintillator. We find that LENA is able to detect deviations from isotropy of the geoneutrino
flux with high significance. However, if only the directional information is used, the time required to distinguish between
different geophysical models is of the order of severals decades. Nonetheless, a high-statistics measurement of the total
geoneutrino flux and its spectrum still provides an extremely useful glance at the Earth’s interior. 相似文献
2.
The giant planetary magnetospheres surrounding Jupiter and Saturn respond in quite different ways, compared to Earth, to changes in upstream solar wind conditions. Spacecraft have visited Jupiter and Saturn during both solar cycle minima and maxima. In this paper we explore the large-scale structure of the interplanetary magnetic field (IMF) upstream of Saturn and Jupiter as a function of solar cycle, deduced from solar wind observations by spacecraft and from models. We show the distributions of solar wind dynamic pressure and IMF azimuthal and meridional angles over the changing solar cycle conditions, detailing how they compare to Parker predictions and to our general understanding of expected heliospheric structure at 5 and 9 AU. We explore how Jupiter’s and Saturn’s magnetospheric dynamics respond to varying solar wind driving over a solar cycle under varying Mach number regimes, and consider how changing dayside coupling can have a direct effect on the nightside magnetospheric response. We also address how solar UV flux variability over a solar cycle influences the plasma and neutral tori in the inner magnetospheres of Jupiter and Saturn, and estimate the solar cycle effects on internally driven magnetospheric dynamics. We conclude by commenting on the effects of the solar cycle in the release of heavy ion plasma into the heliosphere, ultimately derived from the moons of Jupiter and Saturn. 相似文献
3.
Solar System Research - Based on the analysis of the data available in the literature on laboratory measurements of the dielectric characteristics of the lunar soil samples delivered to the Earth... 相似文献
4.
We revisit a set of symplectic variables introduced by Andre Deprit (Celest Mech 30, 181–195, 1983), which allows for a complete symplectic reduction in rotation invariant Hamiltonian systems, generalizing to arbitrary dimension
Jacobi’s reduction of the nodes. In particular, we introduce an action-angle version of Deprit’s variables, connected to the
Delaunay variables, and give a new hierarchical proof of the symplectic character of Deprit’s variables. 相似文献
5.
V. L. Gorshkov 《Solar System Research》2010,44(6):487-497
In this work we investigate the variations of the Earth’s rotation in the interval of periods from 2 to 8 years using the
longest available observational series obtained both by means of astrometry and space geodesy. We found an abrupt change of
the variation pattern in the middle of the 1980s, when classical ground-based astrometric facilities for studying the Earth
Rotation Parameters (ERP) were replaced with space geodesy methods. Variations with a 6-year periodicity and ∼0.2-ms amplitude
practically disappeared (space geodesy instruments did not detect these variations right from the start), but the 2- to 4-year
periodicities increased in amplitude and began to dominate in this frequency range under consideration. In this study, we
analyze some possible excitation sources and possible causes of the change in the variability pattern. 相似文献
6.
G. S. Kurbasova 《Bulletin of the Crimean Astrophysical Observatory》2010,106(1):82-86
The appearance of features with cusp points on the diagrams of changes in the coordinates of the Earth’s instantaneous pole
(polhodes) is considered as the result of mapping onto the plane of its displacement over the surface during the Earth’s rotational-translational
motion. The results of qualitative and quantitative analyses of the data on the coordinates of the Earth’s instantaneous pole
are discussed. The basic principles of the theory of Whitney singularities and their application for explaining the bifurcations
of the equilibrium positions for the Zeeman catastrophe machine (Arnold 1990) are used in the analyses. 相似文献
7.
Paolo Molaro 《Astrophysics and Space Science》2014,354(1):75-81
Absorption systems observed along the line of sights to distant quasars are observed at all redshifts and the full range of the electromagnetic spectrum is needed to recover the variety of transitions of different elements. However, some important elements are found within the Lyman forest and their absorption line profiles need to be analyzed against the presence of possible Ly-α contamination. Considering the cosmological evolution of the number density of hydrogen clouds, the probability to detect uncontaminated metal lines is higher in the UV-Optical region exploited by CUBES. The list of these elements includes some important ones such as D, H2, O?i, N?i, O?vi, Ar?i, P?ii, C?ii, S?ii and B?ii. The determination of some of them in the Damped Ly-α galaxies and their astronomical interest are briefly discussed. 相似文献
8.
In the present paper the equations of the orbital motion of the major planets and the Moon and the equations of the three–axial
rigid Earth’s rotation in Euler parameters are reduced to the secular system describing the evolution of the planetary and
lunar orbits (independent of the Earth’s rotation) and the evolution of the Earth’s rotation (depending on the planetary and
lunar evolution). Hence, the theory of the Earth’s rotation can be presented by means of the series in powers of the evolutionary
variables with quasi-periodic coefficients with respect to the planetary–lunar mean longitudes. This form of the Earth’s rotation
problem is compatible with the general planetary theory involving the separation of the short–period and long–period variables
and avoiding the appearance of the non–physical secular terms. 相似文献
9.
V. V. Sidorenko D. J. Scheeres S. M. Byram 《Celestial Mechanics and Dynamical Astronomy》2008,102(1-3):133-147
We consider the secular effect of outgassing torques on the rotation of a comet nucleus. An averaging method is applied to obtain evolutionary equations which allow us to study the long-term variations in the nucleus spin state. Since the spin axis direction of 19P/Borrelly’s nucleus is close to the line of apsides direction, a simplified version of these equations can be written to analytically study the most important qualitative effects. In particular, a correlation between the drift of the rotation axis direction and the possible spin up/spin down of the nucleus is revealed. 相似文献
10.
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12.
A.D. Fortes 《Planetary and Space Science》2012,60(1):10-17
Titan’s moment of inertia (MoI), estimated from the quadrupole gravity field measured by the Cassini spacecraft, is 0.342, which has been interpreted as evidence of a partially differentiated internal mass distribution. It is shown here that the observed MoI is equally consistent with a fully differentiated internal structure comprising a shell of water ice overlying a low-density silicate core; depending on the chemistry of Titan’s subsurface ocean, the core radius is between 1980 and 2120 km, and its uncompressed density is 2570–2460 kg m?3, suggestive of a hydrated CI carbonaceous chondrite mineralogy. Both the partially differentiated and fully differentiated hydrated core models constrain the deep interior to be several hundred degrees cooler than previously thought. I propose that Titan has a warm wet core below, or buffered at, the high-pressure dehydration temperature of its hydrous constituents, and that many of the gases evolved by thermochemical and radiogenic processes in the core (such as CH4 and 40Ar, respectively) diffuse into the icy mantle to form clathrate hydrates, which in turn may provide a comparatively impermeable barrier to further diffusion. Hence we should not necessarily expect to see a strong isotopic signature of serpentinization in Titan’s atmosphere. 相似文献
13.
A. P. Vidmachenko 《Kinematics and Physics of Celestial Bodies》2017,33(6):291-294
Solar-induced changes in the reflective properties of the visible disk of Jupiter mostly depend on variations in the Earth’s jovimagnetic latitude. Since the orbit of Jupiter is eccentric (the eccentricity is e = 0.04845) and the planet passes perihelion at the time close to the summer solstice, the atmosphere receives 21% more solar energy in the northern hemisphere than in the southern one. According to the results of our studies, the ratio of the brightness values for the northern and southern tropical and temperate zones is a clear indicator of photometric activity of the processes in the atmosphere of Jupiter. From the analysis of the observational data for the period from 1962 to 2017, the cyclicity in changes of the activity factor of the hemispheres of the planet with a period of 11.87 years was found. This suggests that the atmosphere of Jupiter experiences seasonal restructuring. 相似文献
14.
ABHISHEK SHUKLA ANKIT KUMAR PANDEY ANIRBAN PATHAK 《Journal of Astrophysics and Astronomy》2017,38(1):7
In many real life situations, it is observed that the first digits (i.e., 1,2,…,9) of a numerical data-set, which is expressed using decimal system, do not follow a uniform distribution. In fact, the probability of occurrence of these digits decreases in an almost exponential fashion starting from 30.1 % for 1 to 4.6 % for 9. Specifically, smaller numbers are favoured by nature in accordance with a logarithmic distribution law, which is referred to as Benford’s law. The existence and applicability of this empirical law have been extensively studied by physicists, accountants, computer scientists, mathematicians, statisticians, etc., and it has been observed that a large number of data-sets related to diverse problems follow this distribution. However, except two recent works related to astronomy, applicability of Benford’s law has not been tested for extrasolar objects. Motivated by this fact, this paper investigates the existence of Benford’s distribution in the extrasolar world using Kepler data for exoplanets. The quantitative investigations have revealed the presence of Benford’s distribution in various physical properties of these exoplanets. Further, some specific comments have been made on the possible generalizations of the obtained results, its potential applications in analysing the data-set of candidate exoplanets. 相似文献
15.
Badam Singh Kushvah 《Astrophysics and Space Science》2009,323(1):57-63
Linearization of the Hamiltonian is being performed in the generalized photogravitational Chermnykh’s problem. The normal
form of the second order part of the Hamiltonian have been found. The effect of radiation pressure, gravitational potential
from the belt have been examined analytically and numerically 相似文献
16.
B. P. Kondratyev 《Solar System Research》2012,46(5):341-351
The effect of the Earth??s compression on the physical libration of the Moon is studied using a new vector method. The moment of gravitational forces exerted on the Moon by the oblate Earth is derived considering second order harmonics. The terms in the expression for this moment are arranged according to their order of magnitude. The contribution due to a spherically symmetric Earth proves to be greater by a factor of 1.34 × 106 than a typical term allowing for the oblateness. A linearized Euler system of equations to describe the Moon??s rotation with allowance for external gravitational forces is given. A full solution of the differential equation describing the Moon??s libration in longitude is derived. This solution includes both arbitrary and forced oscillation harmonics that we studied earlier (perturbations due to a spherically symmetric Earth and the Sun) and new harmonics due to the Earth??s compression. We posed and solved the problem of spinorbital motion considering the orientation of the Earth??s rotation axis with regard to the axes of inertia of the Moon when it is at a random point in its orbit. The rotation axes of the Earth and the Moon are shown to become coplanar with each other when the orbiting Moon has an ecliptic longitude of L ? = 90° or L ? = 270°. The famous Cassini??s laws describing the motion of the Moon are supplemented by the rule for coplanarity when proper rotations in the Earth-Moon system are taken into account. When we consider the effect of the Earth??s compression on the Moon??s libration in longitude, a harmonic with an amplitude of 0.03?? and period of T 8 = 9.300 Julian years appears. This amplitude exceeds the most noticeable harmonic due to the Sun by a factor of nearly 2.7. The effect of the Earth??s compression on the variation in spin angular velocity of the Moon proves to be negligible. 相似文献
17.
Conditions for the realization of ULF waves with different polarization are formulated and verified with the use of observational
data from the spacecrafts which performed measurements in the earth’s magnetosphere. It is shown that the conditions formulated
are in good agreement with observed wave parameters. 相似文献
18.
A. G. Nikoghossian 《Astrophysics》2009,52(1):1-23
The purpose of this article is to provide some insight into Ambartsumian’s methods in the theory of radiative transfer, their
applications, and further development. Two of these methods are emphasized--the invariance principle and the method of addition
of layers, proposed by Ambartsumian in the 1940’s. The difference between these methods and the classical approach for solving
radiative transfer problems is discussed. We discuss only a small portion of the subsequent work by others that we believe
reveals, in a more intuitive way, the essence and significance of Ambartsumian’s methods and their efficiency for applications.
Thus, for example, a separate section is devoted to applications of the Lagrangian formalism to radiative transfer and it
is shown that the invariance principle is a special case of a more general variational principle that reflects an invariance
with respect to translational transformation of the optical depth. Our discussion of the method of addition of layers points
out its generality and the major role it has played in the later creation of such methods as Bellman’s invariant imbedding
method and the method for solving radiative transfer problems in inhomogeneous media. The latter method has yielded a number
of new analytic results. The concluding section is a brief summary of Ambartsumian’s results in the nonlinear theory of radiative
transfer, where he was a pioneer in the study of the class of multilevel problems. This article also sets out to demonstrate
the place and role of Ambartsumian’s methods in the theory of radiative transfer, which, to a great extent, set the path along
which this theory developed for many years to come.
Translated from Astrofizika, Vol. 52, No. 1, pp. 5–27 (February 2009). 相似文献
19.
Stodilka M. I. Sukhorukov A. V. Prysiazhnyi A. I. 《Kinematics and Physics of Celestial Bodies》2019,35(5):231-251
Kinematics and Physics of Celestial Bodies - Abstract—From 2D-spectral observation data of a quiet region of the solar disk center in the Fe I λ 557.609 nm line, 3D hydrodynamic models... 相似文献
20.
Mohamed E. Hassani 《Astrophysics and Space Science》2010,326(1):33-38
In this work we propose cyclical reversible transitions as the scenario in which the universe evolves, through a series consisting of reversible expansion, temporary stability,
and contraction. Our model is based on the comparison between local and global time-dependent densities {ρ
0(τ
0),ρ(τ)} instead of the critical density ρ
c, local and global time-dependent Hubble parameters {H
0(τ
0),H(τ)}, and the variations {Δρ(τ),ΔH(τ)} due to cosmological chaotic fluctuations, which are generally ignored in certain oscillating models. By taking into account
all these factors, a rate equation in the form of (H
0/H)2
∝(ρ
0/ρ) has been established, and from it we derive some others, to provide a mechanism that is responsible for the cyclical reversible
transitions. Also, the problems of singularities, black hole overproduction, and the second law of thermodynamics arising
in oscillating universe models are conceptually resolved. 相似文献