Gravimetric Methods – Superconducting Gravity Meters

Hinderer, J.; Crossley, David; Warburton, Richard J.

doi:10.1016/b978-044452748-6.00172-3

Cited by 66 publications

(64 citation statements)

References 162 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As already stated by Grinfeld & Wisdom (2005), the gravity anomaly due to the Slichter mode increases with increasing size of the inner core and can be up to two orders of magnitude greater than the expected gravity anomaly due to the Slichter mode of the Earth (less than 1 ngal, Hinderer et al 2007) for a very large inner core. As the center of mass of Mercury remains fixed during a Slichter mode oscillation, gravity anomalies due to this mode cannot be measured from orbit.…”

Section: Slichter Modes Detectionmentioning

confidence: 61%

Period of the Slichter mode of Mercury and its possible observation

Coyette

Hoolst

Déhant

2012

A&A

View full text Add to dashboard Cite

Aims. We study the period of the Slichter mode (vibrational mode of the inner core of a planet) of Mercury in relation to its interior structure and assess the possibility to observe this mode with the probes MESSENGER and BepiColombo. Methods. The methodology of Grinfeld & Wisdom (2005, Phys. Earth Planet. Int., 151, 77) for the determination of the period of the polar Slichter modes of a planetary interior consisting of three homogeneous layers is generalized to models with an arbitrary but finite number of layers. Slichter modes periods are calculated for a large set of interior structure models of Mercury. We study the possible excitation of Slichter modes by a colllision with a meteoroid and estimate the minimal size of the meteoroid that could lead to a detection of these modes by BepiColombo. Results. The Slichter mode period obtained is on the order of several hours. Observation of the Slichter mode of Mercury allows constraining the inner core. An impact by a meteoroid with a radius of at least 100 m could excite the Slichter mode to a level observable by BepiColombo (assuming that the Slichter mode is the only excited mode), but since the estimated damping time of the Slichter mode is well below the average time between impacts of at least that size such an impact must have occured recently (less than 0.5 My ago).

show abstract

Section: Slichter Modes Detectionmentioning

confidence: 61%

Period of the Slichter mode of Mercury and its possible observation

Coyette

Hoolst

Déhant

2012

A&A

View full text Add to dashboard Cite

show abstract

“…In contrast, Zürn and Widmer (1995) pointed out that noise reduction is also possible in the frequency band of the lowest degree free oscillations using a simple regression method and locally recorded barometric pressure. The regression factor is about 3.5 nm·s −2 /hPa and is now routinely applied for noise reduction in records from (superconducting) gravimeters (e. g. Hinderer et al, 2007). Examples are presented for instance in Zürn and Widmer (1995), Virtanen (1996), Van Camp (1999), Zürn et al (2000), Rosat et al (2003) and Zürn and Wielandt (2007, Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Significant research effort has been devoted to atmospheric effects on gravity records at very long periods (e.g. Hinderer et al, 2007). In contrast, Zürn and Widmer (1995) pointed out that noise reduction is also possible in the frequency band of the lowest degree free oscillations using a simple regression method and locally recorded barometric pressure.…”

Section: Introductionmentioning

confidence: 99%

Clear evidence for the sign-reversal of the pressure admittance to gravity near 3mHz

Zürn¹,

Meurers

2009

Journal of Geodynamics

View full text Add to dashboard Cite

SUMMARYThe influence of the atmosphere on gravity measurements by Newtonian attraction and vertical displacements due to surface loading is well known and studied especially at frequencies below 1 mHz. Less work has been done at the higher seismic frequencies where inertial effects come into play. The sensor mass of a vertical accelerometer responds to several forces caused by the atmosphere, on global, regional and local scales. For the seismic frequencies the atmosphere above the observation site has the largest influence. A simple "Gedankenexperiment" demonstrates that the gravitational effect on one hand and the free air and inertial effects due to deformation on the other have opposite sign. Since the inertial effect is strongly frequency-dependent there should be a crossover-frequency where the pressure admittance to gravity changes sign. Simple analytical models clearly show this property near frequencies of a few mHz and are used here to amplify the variance reduction of the gravity residuals. The crossover-frequency depends on the properties of the models of the atmospheric phenomena and the elasticity of the Earth's crust. Therefore in reality it must be expected to vary in time and space.We show one extremely clear example of this sign-reversal detected in the gravity data from the superconducting gravimeter GWR-C025 in Vienna among other examples which demonstrate the reality of this effect.

show abstract

“…The spectral analysis of these signals would provide the free frequency of the motion which, as we have pointed out, contains information about some physical internal properties of the icy body. In fact, this method has been widely used in the study of the free modes of oscillation of the Earth, although there is still great controversy as regarding the detection of the Slichter triplet (e.g., Hinderer et al 2007).…”

Section: Discussionmentioning

confidence: 99%

“…The modeling and observational detection of these frequencies have received much attention in recent years since their knowledge will provide valuable information about the Earth's interior. This has acquired a new focus with the advent of superconducting gravimeters (e.g., Hinderer et al 2007).…”

Section: Earth Internal Translational Motionsmentioning

confidence: 99%

Free Translational Oscillations of Icy Bodies With a Subsurface Ocean Using a Variational Approach

Escapa

Fukushima

2011

The Astronomical Journal

View full text Add to dashboard Cite

We analyze the influence of the interior structure of an icy body with an internal ocean on the relative translational motions of its solid constituents. We consider an isolated body differentiated into three homogeneous layers with spherical symmetry: an external ice-I layer, a subsurface ammonia-water ocean, and a rocky inner core. This composition represents icy bodies such as Europa, Titania, Oberon, and Triton, as well as Pluto, Eris, Sedna, and 2004 DW. We construct the equations of motion by assuming that the solid constituents are rigid and that the ocean is an ideal fluid, the internal motion being characterized by the relative translations of the solids and the induced flow in the fluid. Then we determine the dynamics of the icy body using the methods of analytical mechanics, that is, we compute the kinetic energy and the gravitational potential energy, and obtain the Lagrangian function. The resulting solution of the Lagrange equations shows that the solid layers perform translational oscillations of different amplitudes with respect to the barycenter of the body. We derive the dependence of the frequency of the free oscillations of the system on the characteristics of each layer, expressing the period of the oscillations as a function of the densities and masses of the ocean and the rocky inner core, and the mass of the icy body. We apply these results to previously developed subsurface models and obtain numerical values for the period and the ratio between the amplitudes of the translational oscillations of the solid components. The features obtained are quite different from the cases of Earth and Mercury. Our analytical formulas satisfactorily explain the source of these differences. When models of the same icy body, compatible with the existence of an internal ocean, differ in the thickness of the ice-I layer, their associated periods experience a relative variation of at least 10%. In particular, the different models for Titania and Oberon exhibit a larger variation of about 37% and 30%. This indicates an absolute difference of the order of three and two hours, respectively. This suggests that the free period of the internal oscillations might provide a new procedure to constrain the internal structure of icy bodies with a subsurface ocean.

show abstract

Gravimetric Methods – Superconducting Gravity Meters

Cited by 66 publications

References 162 publications

Period of the Slichter mode of Mercury and its possible observation

Period of the Slichter mode of Mercury and its possible observation

Clear evidence for the sign-reversal of the pressure admittance to gravity near 3mHz

Free Translational Oscillations of Icy Bodies With a Subsurface Ocean Using a Variational Approach

Contact Info

Product

Resources

About