55 research outputs found
Mach's Principle
We briefly review the history of Mach's principle and discuss its
significance in the light of modern physics.Comment: 20 pages; v2: improved version published as the second chapter of The
Measurement of Gravitomagnetism: A Challenging Enterprise, edited by L. Iorio
(Nova Science, New York, 2007), pp. 13-2
Some aspects on the observation of the gravitomagnetic clock effect
http://arxiv.org/abs/gr-qc/0101089As a consequence of gravitomagnetism, which is a fundamental weak-field prediction of general relativity and ubiquitous in gravitational phenomena, clocks show a difference in their proper periods when moving along identical orbits in opposite directions about a spinning mass. This time shift is induced by the rotation of the source and may be used to verify the existence of the terrestrial gravitomagnetic field by means of orbiting clocks. A possible mission scenario is outlined with emphasis given to some of the major difficulties which inevitably arise in connection with such a venture
An alternative derivation of the gravitomagnetic clock effect
The possibility of detecting the gravitomagnetic clock effect using
artificial Earth satellites provides the incentive to develop a more intuitive
approach to its derivation. We first consider two test electric charges moving
on the same circular orbit but in opposite directions in orthogonal electric
and magnetic fields and show that the particles take different times in
describing a full orbit. The expression for the time difference is completely
analogous to that of the general relativistic gravitomagnetic clock effect in
the weak-field and slow-motion approximation. The latter is obtained by
considering the gravitomagnetic force as a small classical non-central
perturbation of the main central Newtonian monopole force. A general expression
for the clock effect is given for a spherical orbit with an arbitrary
inclination angle. This formula differs from the result of the general
relativistic calculations by terms of order c^{-4}.Comment: LaTex2e, 11 pages, 1 figure, IOP macros. Submitted to Classical and
Quantum Gravit
Three-Dimensional Modeling of Callisto's Surface Sputtered Exosphere Environment
We study the release of various elements from Callisto's surface into its
exosphere by plasma sputtering. The cold Jovian plasma is simulated with a 3D
plasma-planetary interaction hybrid model, which produces 2D surface
precipitation maps for magnetospheric H+ , O+ , O++ , and S++ . For the hot
Jovian plasma, we assume isotropic precipitation onto the complete spherical
surface. Two scenarios are investigated: One where no ionospheric shielding
takes place and accordingly full plasma penetration is implemented ('no
ionosphere' scenario), and one where an ionosphere lets virtually none of the
cold plasma but all of the hot plasma reach Callisto's surface ('ionosphere'
scenario). In the 3D exosphere model, neutral particles are sputtered from the
surface and followed on their individual trajectories. The 3D density profiles
show that whereas in the 'no ionosphere' scenario the ram direction is favored,
the 'ionosphere' scenario produces almost uniform density profiles. In
addition, the density profiles in the 'ionosphere' scenario are reduced by a
factor of ~2.5 with respect to the 'no ionosphere' scenario. We find that the
Neutral gas and Ion Mass spectrometer, which is part of the Particle
Environment Package on board the JUICE mission, will be able to detect the
different sputter populations from Callisto's icy surface and the major sputter
populations from Callisto's non-icy surface. The chemical composition of
Callisto's exosphere can be directly linked to the chemical composition of its
surface, and will offer us information not only on Callisto's formation
scenario but also on the building blocks of the Jupiter system.Comment: Published in JGR: Space Physic
On the Possibility of Measuring the Gravitomagnetic Clock Effect in an Earth Space-Based Experiment
In this paper the effect of the post-Newtonian gravitomagnetic force on the
mean longitudes of a pair of counter-rotating Earth artificial satellites
following almost identical circular equatorial orbits is investigated. The
possibility of measuring it is examined. The observable is the difference of
the times required to in passing from 0 to 2 for both senses of
motion. Such gravitomagnetic time shift, which is independent of the orbital
parameters of the satellites, amounts to 5 s for Earth; it is
cumulative and should be measured after a sufficiently high number of
revolutions. The major limiting factors are the unavoidable imperfect
cancellation of the Keplerian periods, which yields a constraint of 10
cm in knowing the difference between the semimajor axes of the satellites,
and the difference of the inclinations of the orbital planes which, for
, should be less than . A pair of spacecrafts
endowed with a sophisticated intersatellite tracking apparatus and drag-free
control down to 10 cm s Hz level might allow to meet
the stringent requirements posed by such a mission.Comment: LaTex2e, 22 pages, no tables, 1 figure, 38 references. Final version
accepted for publication in Classical and Quantum Gravit
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
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