Tidal forces in Bocharova–Bronnikov–Melnikov–Bekenstein spacetime

Tidal gravity changes arise from the response of the solid Earth to the tidal forces of the Sun, Moon and planets close to the Earth, and are a comprehensive reflection of the structure and distribution of physical properties of the Earth’s interior. As a result, observations of tidal gravity changes are the basis of studies on other global and/or regional dynamic processes. The characteristics of tidal gravity changes in the region of the Tibetan Plateau were investigated through continuous gravity measurements recorded with a superconducting gravimeter (SG) installed in Lhasa over a year. Through contrast measurements with a spring gravimeter LaCoste-Romberg ET20 at the same site, the gravity observations in Lhasa were scaled to the international tidal gravity reference in Wuhan. Meanwhile, the scale factor of the SG was determined accurately as −777.358 ± 0.136 nm s−2 V−1, which is about 2.2% less than the value provided by the manufacturer. The results indicate that the precision of the tidal gravity observations made with the SG in Lhasa was very high. The standard deviation was 0.459 nm s−2, and the uncertainties of for the four main tidal waves (i.e. O1, K1, M2 and S2) were better than 0.006%. In addition, the observations of the diurnal gravity tides had an obvious pattern of nearly diurnal resonance. As a result, it is affirmed that the Lhasa station can provide a local tidal gravity reference for gravity measurements on the Tibetan Plateau and its surrounding regions. The loading effects of oceanic tides on tidal gravity observations in Lhasa are so weak that the resulting perturbations in the gravimetric factors are less than 0.6%. However, the loading effects of the local atmosphere on either the tidal or nontidal gravity observations are significant, although no seasonal variations were found. After removal of the atmospheric effects, the standard deviation of the SG observations in Lhasa decreased obviously from 2.009 to 0.459 nm s−2. Having removed the loading effects of oceanic tides and local atmosphere, it was found that the tidal gravity observations made with the SG in Lhasa significantly differed by about 1% from those expected theoretically, which may be related to active tectonic movement and the extremely thick crust in the region of the Tibetan Plateau. A more-certain conclusion requires longer accumulation of SG data and further associated theoretical studies.

An approach for simulating storm surge events was investigated and presented in this work. The storm surge event that occurred in the North of Portugal (Viana do Castelo), during the period of 14th-16th October 1987 was considered. In the definition of the computational domain, the path of the storm was considered, among other aspects. A tidal harmonic analysis was made to the tide gauge observations to extract the tidal components, enabling the determination of the sea level residuals. The ADCIRC model was used for the hydrodynamic modeling, which included different forcing mechanisms. Simulations were carried out for evaluating the model performance and to investigate possible nonlinear interactions between tidal and meteorological forcing. In this way, three types of simulations were carried out: modeling of the astronomical tides, with tidal forcing at the open boundary; modeling of the storm surge, using meteorological forcing only, and simulations including both tidal and meteorological forcing. Results show that there is some non-linear interaction between astronomical and meteorological forcing and that the observed sea levels are partially explained by this forcing. It was concluded that to obtain a better reproduction of the storm event, further simulations are required.

The combined observation of gravitational and electromagnetic waves from the coalescence of two neutron stars marks the beginning of multi-messenger astronomy with gravitational waves (GWs). The development of accurate gravitational waveform models is a crucial prerequisite to extract information about the properties of the binary system that generated a detected GW signal. In binary neutron star systems (BNS), tidal effects also need to be incorporated in the modeling for an accurate waveform representation. Building on previous work [Phys.Rev.D96 121501], we explore the performance of inspiral-merger waveform models that are obtained by adding a numerical relativity (NR) based approximant for the tidal part of the phasing (NRTidal) to existing models for nonprecessing and precessing binary black hole systems (SEOBNRv4, PhenomD and PhenomPv2), as implemented in the LSC Algorithm Library Suite. The resulting BNS waveforms are compared and contrasted to target waveforms hybridizing NR waveforms, covering the last approx. 10 orbits up to merger and extending through the postmerger phase, with inspiral waveforms calculated from 30Hz obtained with TEOBResumS. The latter is a state-of-the-art effective-one-body waveform model that blends together tidal and spin effects. We probe that the combination of the PN-based self-spin terms and of the NRTidal description is necessary to obtain minimal mismatches (< 0.01) and phase differences (< 1 rad) with respect to the target waveforms. However, we also discuss possible improvements and drawbacks of the NRTidal approximant in its current form, since we find that it tends to overestimate the tidal interaction with respect to the TEOBResumS model during the inspiral.

Effects of location, diel period, tidal condition and water clanty on the size and distribution of the shallow water fish assemblage of the non-estuarine Kuwait Bay, were investigated using a beach seine and a small research trawl during spring and summer 1989. Total numbers, biomass and numbers of species differed markedly between Doha, a sandy shore environment, and Kazmah, an extensive intertidal mud flat. When fish were present in large numbers there was a marked die1 effect at both locat~ons with many more fish captured during the mght. Tidal effects were influenced by turbidity and the age structure of the assemblage. In clear water during spring, very young Liza carinata from the seine catches formed shoals at the edge of the rising tide both day and night, while fish 2 mo older formed shoals only on daytime r~s ing tides. At Kazmah during spnng, h ~ g h turbidity obscured any tidal effects in the seine catches. In shghtly deeper water, sampled by trawl during spring, Leioynathus decorus showed an asymmetrical hdal migration In summer, beach seine catches were much higher on the rising tide. Summer trawl catches did not show a consistent tidal effect

This paper presents a numerical modeling study of tidal effects on groundwater dynamics of a multi-layered estuary aquifer system. In this study, to generalize the tidal loading effects on the confined aquifer, we used equivalent tidal loading boundary condition based on existing analytical solutions for the confined aquifer in a three-dimensional numerical model and then good simulated result was obtained. Using the numerical model, the tide-induced groundwater level and confined groundwater discharge dynamics were discussed and the following conclusions were obtained. The combined action of sea tide and river tide can enhance the tidal response of groundwater level in the aquifer system, especially for the confined groundwater. The river tidal effect is more significant in the areas away from coastline. Although the confined aquifer is separated by a layer of clay from the ocean, because of the tidal loading effects, the confined groundwater discharge also changes periodically displaying a negative correlation with the tide level fluctuations like the unconfined groundwater discharge. Using linear functions that express the relationship between the mean confined groundwater flux and sea tide level, the confined groundwater flux through the tidal loading boundaries can be approximately estimated. When the sea tide level is higher than 4.4 m, there would be a risk of seawater intrusion into the confined aquifer in the study area. This case study is useful for numerical studying of tidal effects on groundwater resource dynamics in a coastal multi-layered estuary aquifer system.

Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which doesn't suffer of the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extension of the Riccati method to investigate dynamic tides in close binaries. We demonstrate CAFein's capabilities as a stellar pulsation code both in the adiabatic and non-adiabatic regime, by reproducing previously published eigenfrequencies of a polytrope, and by successfully identifying the unstable modes of a stellar model in the $\beta$ Cephei/SPB region of the Hertzsprung-Russell diagram. Finally, we verify CAFein's behavior in the dynamic tides regime by investigating the effects of dynamic tides on the eigenfunctions and orbital and spin evolution of massive Main Sequence stars in eccentric binaries, and of hot Jupiter host stars. The plethora of asteroseismic data provided by the NASA's Kepler satellite, some of which include the direct detection of tidally excited stellar oscillations, make CAFein quite timely. Furthermore, the increasing number of observed short-period detached double white dwarfs (WD) and the observed orbital decay in the tightest of such binaries open up a new possibility of investigating WD interiors through the effects of tides on their orbital evolution

Properties and evolution of NEO families created by tidal disruption at Earth

It is a major misconception that freely falling reference frames are inertial in a gravitational field. This is one outcome when employing Einstein’s principle of equivalence between a dynamical acceleration and a homogeneous gravity, which does not exist technically in nature, because gravity is radial from all mass centers, even at nearly infinite distances between masses. Even though floating objects within a space station orbiting Earth appear to move with constant inertial velocities, tidal forces exist to accelerate all such objects. The four oceanic tides of Earth prove that the Moon and Sun are the two external gravitational bodies pulling on Earth, even if an earthbound observer cannot physically feel the tidal forces. Theoretical experiments demonstrate how to observe tidal effects internally to determine the external gravitational forces. Tidal forces make dumbbell-shaped artificial satellites rotate around a heavenly body once per orbit. A liquid in free fall like mercury becomes prolate in shape and aligns with the external gravitational force if the liquid’s surface tension can be minimized. Today’s technology is very precise and can detect most subtle forces, so that local experiments can distinguish between a reference frame in free fall versus a truly inertial frame placed far away from gravitational bodies. Tidal forces always exist in any neighborhood of a test mass due to the radial gravitational force from any external mass, so the mathematical limit of a shrinking local reference frame always contains tidal forces within its domain. Thus, Einstein’s equivalence principle is an approximation and is technically applicable for only point masses.

Tidal dynamical considerations constrain the state of an ocean on Enceladus

Hydrodynamic processes in river mouths represent a complex interplay of fluvial discharge, tidal influence, and saline intrusion. Standard marine flow and discharge measurement techniques face significant limitations in estuarine zones, particularly near river mouths, due to complex bidirectional flow patterns and the influence of tidal and saline forces. The peculiar characteristic of the microtidal regime in the northern Adriatic Sea makes the understanding of the hydrodynamic processes at the river mouth extremely complex. Moreover, the Isonzo basin climate condition varies from alpine to sub-Mediterranean. Thus, can introduce large variations in the flow rate of the river (related to precipitation), amplifying an already pronounced intra- and inter-annual variability due to the torrential regime and prolongated drought season.In this work, we focus on the monitoring system of the Isonzo Current meter, an ADCP (Acoustic Doppler Current Profiler) station fixed at a depth of 13 meters from the river surface, located 7 km far from the Delta Inlet in the Northern Adriatic Sea. The station, operative since 2005, acquires and transmits data every 10 minutes. Continuous measurements of river flow velocity, flow direction, temperature and calculation of the flow rate, have enabled the identification of two distinct river flow regimes: 1) normal condition of low freshwater discharge related to high rising tide and/or drought period, and 2) exceptional high discharge related to freshwater flood events.In normal and drought conditions we observe that the river water column present an average direction upstream related to: a) marine water intruding the river, b) variation of the river high coinciding to the diurnal tidal modulation, c) discharge fluctional related to the maximum and minim tide, d) stratified water column in the central portion with thin mixing layer at the bottom and surface of the river section, and e) a high temperature (related to the marine water temperature) at the riverbed.In opposition, during flood events, the flow direction becomes homogeneous in the entire water column, discharging downstream and pushing the tidal force outside the river. The onset of a flood event records a sharp thermal drop, indicating the replacement of the marine water by freshwater throughout the channel and the flow rates can exceed 2500 m³/s.The presence of a semi-stationary salt wedge intrusion in the river was identified and wide. However, it is not clear how the tide and the river runoff interact in the water mass exchanges, or what are the water mixed or stratified condition in different hydrodynamic regime. These results are essential for understanding estuarine dynamics, particularly in a climate context marked by increasingly frequent extreme events.

A study combining a sediment-seawater microcosm with multimedia fugacity model to evaluate the effect of tidal cycles on polycyclic aromatic hydrocarbon release from sediments

This paper discusses tidal effects on an observation scheme to determine a point at the bottom of the sea by combining GPS and Sonar observations. For the purpose, three kinds of Earth tides are introduced (i.e., the crust tide, the equipotential surface point (ocean depth) tide, and the geoid tide). The corresponding mathematical expressions are derived to demonstrate the tidal effects on GPS and Sonar observations. The relations between the Earth tides are also discussed. Theoretical results imply a very interesting conclusion, namely that, for a local area, the static position of a point at the bottom of sea can be obtained by the dynamic observations without any tidal correction. Actually, the tidal effects cancel each other in the mentioned observation scheme. It therefore indicates that the observation scheme is free of tidal effects. Furthermore, we learned that the divergence caused by any error source on ocean surface is canceled and does not affect the final results. Therefore, to determine the position of a point at the bottom of sea, we need not consider any tidal effects.

The tidal effect is a main error source in GNSS positioning. It is analyzed in detail by tide computation and practical data processing in this paper. The results show that the effect of the tide on static and kinematic positioning is related to the observation time, the station location and the length of baseline, respectively. The tidal effect on coastal stations is greater than that on inland stations. The difference of the tidal effect is great even for nearby coastal stations. However, the effect shows zonal distribution for inland stations. Therefore, it has to be taken into account even for a relative small coastal GNSS network. Static GNSS data kinematic processing experiment and airborne kinematic GNSS data processing experiment are done in this paper, and the results show that the tidal effect can be detected by GNSS surveying.

We report the results of N-body simulations of disrupting satellites aimed at exploring whether the observed features of dSphs can be accounted for with simple, mass-follows-light (MFL) models including tidal disruption. As a test case, we focus on the Carina dwarf spheroidal (dSph), which presently is the dSph system with the most extensive data at large radius. We find that previous N-body, MFL simulations of dSphs did not sufficiently explore the parameter space of satellite mass, density, and orbital shape to find adequate matches to Galactic dSph systems, whereas with a systematic survey of parameter space we are able to find tidally disrupting, MFL satellite models that rather faithfully reproduce Carina's velocity profile, velocity dispersion profile, and projected density distribution over its entire sampled radius. The successful MFL model satellites have very eccentric orbits, currently favored by CDM models, and central velocity dispersions that still yield an accurate representation of the bound mass and observed central M/L ~ 40 of Carina, despite inflation of the velocity dispersion outside the dSph core by unbound debris. Our survey of parameter space also allows us to address a number of commonly held misperceptions of tidal disruption and its observable effects on dSph structure and dynamics. The simulations suggest that even modest tidal disruption can have a profound effect on the observed dynamics of dSph stars at large radii. Satellites that are well described by tidally disrupting MFL models could still be fully compatible with ΛCDM if, for example, they represent a later stage in the evolution of luminous subhalos.

We consider the problem of tidal disruption of stars in the centre of a galaxy containing a supermassive binary black hole with unequal masses. We assume that over the separation distance between the black holes the gravitational potential is dominated by the more massive black hole. Also, we assume that the number density of stars is concentric with the primary black hole and has a power law cusp.We show that the bulk of stars with a small angular-momentum component normal to the black hole binary orbit can reach a small value of total angular momentum through secular evolution in the gravitational field of the binary, and hence they can be tidally disrupted. This effect is analogous to the so-called Kozai effect (Kozai, 1962, Lidov, 1961,1962) well known in celestial mechanics. We develop an analytical theory of secular evolution of the stellar orbits and calculate the rate of tidal disruption. We confront our analytical theory with a simple numerical model and find very good agreement. Our results show that for primary black-hole mass \sim 10^{6}-10^{7}M_{\odot}, the black- hole mass ratio q > 10^{-2}, cusp size \sim 1pc, the tidal disruption rate can be as large as \sim 10^{-2}-1M_{\odot}/yr. This is at least 10^{2}-10^{4} times larger than estimated for the case of a single supermassive black hole. The duration of the phase of enhanced tidal disruption is determined by the dynamical friction time scale, and it is rather short: \sim 10^{5}yr. The dependence of the tidal disruption rate on the mass ratio, as well as on the size of the cusp, is also discussed.