132 research outputs found
The impact of the new CHAMP and GRACE Earth gravity models on the measurement of the general relativistic Lense--Thirring effect with the LAGEOS and LAGEOS II satellites
Among the effects predicted by the General Theory of Relativity for the
orbital motion of a test particle, the post-Newtonian gravitomagnetic
Lense-Thirring effect is very interesting and, up to now, there is not yet an
undisputable experimental direct test of it. To date, the data analysis of the
orbits of the existing geodetic LAGEOS and LAGEOS II satellites has yielded a
test of the Lense-Thirring effect with a claimed accuracy of 20%-30%. According
to some scientists such estimates could be optimistic. Here we wish to discuss
the improvements obtainable in this measurement, in terms of reliability of the
evaluation of the systematic error and reduction of its magnitude, due to the
new CHAMP and GRACE Earth gravity models.Comment: LaTex2e, 6 pages, no figures, no tables. Paper presented at 2nd CHAMP
science meeting, Potsdam, 1-4 September 200
Conservative evaluation of the uncertainty in the LAGEOS-LAGEOS II Lense-Thirring test
We deal with the test of the general relativistic gravitomagnetic
Lense-Thirring effect currently ongoing in the Earth's gravitational field with
the combined nodes \Omega of the laser-ranged geodetic satellites LAGEOS and
LAGEOS II.
One of the most important source of systematic uncertainty on the orbits of
the LAGEOS satellites, with respect to the Lense-Thirring signature, is the
bias due to the even zonal harmonic coefficients J_L of the multipolar
expansion of the Earth's geopotential which account for the departures from
sphericity of the terrestrial gravitational potential induced by the
centrifugal effects of its diurnal rotation. The issue addressed here is: are
the so far published evaluations of such a systematic error reliable and
realistic? The answer is negative. Indeed, if the difference \Delta J_L among
the even zonals estimated in different global solutions (EIGEN-GRACE02S,
EIGEN-CG03C, GGM02S, GGM03S, ITG-Grace02, ITG-Grace03s, JEM01-RL03B, EGM2008,
AIUB-GRACE01S) is assumed for the uncertainties \delta J_L instead of using
their more or less calibrated covariance sigmas \sigma_{J_L}, it turns out that
the systematic error \delta\mu in the Lense-Thirring measurement is about 3 to
4 times larger than in the evaluations so far published based on the use of the
sigmas of one model at a time separately, amounting up to 37% for the pair
EIGEN-GRACE02S/ITG-Grace03s. The comparison among the other recent GRACE-based
models yields bias as large as about 25-30%. The major discrepancies still
occur for J_4, J_6 and J_8, which are just the zonals the combined
LAGEOS/LAGOES II nodes are most sensitive to.Comment: LaTex, 12 pages, 12 tables, no figures, 64 references. To appear in
Central European Journal of Physics (CEJP
How to reach a few percent level in determining the Lense-Thirring effect?
In this paper we discuss and compare a node-only LAGEOS-LAGEOS II combination
and a node-only LAGEOS-LAGEOS II-Ajisai-Jason1 combination for the
determination of the Lense-Thirring effect. The new combined EIGEN-CG01C Earth
gravity model has been adopted. The second combination cancels the first three
even zonal harmonics along with their secular variations but introduces the
non-gravitational perturbations of Jason1. The first combination is less
sensitive to the non-conservative forces but is sensitive to the secular
variations of the uncancelled even zonal harmonics of low degree J4 and J6
whose impact grows linearly in time.Comment: Latex2e, 22 pag. 1 table, 2 figures, 45 references. Changes in the
Abstract, Introduction and Conclusions. Discussion on the non-gravitational
perturbations on Ajisai and on the impact of the secular rates of the even
zonal harmonics added. EIGEN-CG01C CHAMP+GRACE+terrestrial
gravimetry/altimetry Earth gravity model used. Reference adde
Constraints from orbital motions around the Earth of the environmental fifth-force hypothesis for the OPERA superluminal neutrino phenomenology
It has been recently suggested by Dvali and Vikman that the superluminal
neutrino phenomenology of the OPERA experiment may be due to an environmental
feature of the Earth, naturally yielding a long-range fifth force of
gravitational origin whose coupling with the neutrino is set by the scale M_*,
in units of reduced Planck mass. Its characteristic length lambda should not be
smaller than one Earth's radius R_e, while its upper bound is expected to be
slightly smaller than the Earth-Moon distance (60 R_e). We analytically work
out some orbital effects of a Yukawa-type fifth force for a test particle
moving in the modified field of a central body. Our results are quite general
since they are not restricted to any particular size of lambda; moreover, they
are valid for an arbitrary orbital configuration of the particle, i.e. for any
value of its eccentricity . We find that the dimensionless strength coupling
parameter alpha is constrained to |alpha| <= 1 10^-10-4 10^-9 for 1 R_e <=
lambda <= 10 R_e by the laser data of the Earth's artificial satellite LAGEOS
II, corresponding to M_* >= 4 10^9 -1.6 10^10. The Moon perigee allows to
obtain |alpha| <= 3 10^-11 for the Earth-Moon pair in the range 15 R_e <=
lambda = 3 10^10 - 4.5 10^10. Our results
are neither necessarily limited to the superluminal OPERA scenario nor to the
Dvali-Vikman model, in which it is M_* = 10^-6 at lambda = 1 R_e, in contrast
with our bounds: they generally extend to any theoretical scenario implying a
fifth-force of Yukawa-type.Comment: LaTex2e, 18 pages, 4 figures, 1 table, 81 reference
Phenomenology of the Lense-Thirring effect in the Solar System
Recent years have seen increasing efforts to directly measure some aspects of
the general relativistic gravitomagnetic interaction in several astronomical
scenarios in the solar system. After briefly overviewing the concept of
gravitomagnetism from a theoretical point of view, we review the performed or
proposed attempts to detect the Lense-Thirring effect affecting the orbital
motions of natural and artificial bodies in the gravitational fields of the
Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of
the impact of several sources of systematic uncertainties of dynamical origin
to realistically elucidate the present and future perspectives in directly
measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in
Astrophysics and Space Science (ApSS). Some uncited references in the text
now correctly quoted. One reference added. A footnote adde
Recommended from our members
Spectral and spatial decomposition of lithospheric magnetic field models using spherical Slepian functions
Global magnetic field models are typically expressed as spherical-harmonic expansion coefficients. Slepian functions are linear combinations of spherical harmonics that produce new basis functions, which vanish approximately outside chosen geographical boundaries but also remain orthogonal within the spatial region of interest. Hence, they are suitable for decomposing
spherical-harmonic models into portions that have significant magnetic field strength only in selected areas. Slepian functions are spatio-spectrally concentrated, balancing spatial bias and spectral leakage. Here, we employ them as a basis to decompose the global lithospheric
magnetic field model MF7 up to degree and order 72, into two distinct regions. One of the resultant fields is concentrated within the ensemble of continental domains, and the other is localized over its complement, the oceans. Our procedure neatly divides the spectral power at each harmonic degree into two parts. The field over the continents dominates the overall crustal magnetic field, and each region has a distinct power-spectral signature. The oceanic power spectrum is approximately flat, while that of the continental region shows increasing power as the spherical-harmonic degree increases.We provide a further breakdown of the field into smaller, non-overlapping continental and oceanic regions, and speculate on the source of the variability in their spectral signatures
Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions
We put model-independent, dynamical constraints on the net electric charge Q
of some astronomical and astrophysical objects by assuming that their exterior
spacetimes are described by the Reissner-Nordstroem metric, which induces an
additional potential U_RN \propto Q^2 r^-2. Our results extend to other
hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as
well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version
matching the one at press in General Relativity and Gravitation (GRG). arXiv
admin note: substantial text overlap with arXiv:1112.351
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