scholarly journals Nutation in Space and Diurnal Nutation in the Case of an Elastic Earth

1979 ◽  
Vol 82 ◽  
pp. 169-174 ◽  
Author(s):  
Nicole Capitaine
Keyword(s):  
Rotation Axis ◽  
Liquid Core ◽  
Elastic Earth ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior

In order to improve the representation of nutation, the effect of elasticity of the Earth on the nutation in space and diurnal nutation of the terrestrial rotation axis is considered and its amplitude is evaluated for the principal terms. The choice between several methods taking this effect into account is discussed. A comparison with the effect induced on nutation by the existence of a liquid core in the Earth's interior shows that the consideration of elasticity alone cannot give any amelioration in the representation of nutation.

scholarly journals Geosystemics View of Earthquakes

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 412 ◽  
Author(s):  
Angelo De Santis ◽  
Cristoforo Abbattista ◽  
Lucilla Alfonsi ◽  
Leonardo Amoruso ◽  
Saioa A. Campuzano ◽  
...  
Keyword(s):  
Solid Earth ◽  
Point Of View ◽  
Satellite Observations ◽  
Earth System ◽  
Seismic Sequences ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior ◽  
Physical Quantities

Earthquakes are the most energetic phenomena in the lithosphere: their study and comprehension are greatly worth doing because of the obvious importance for society. Geosystemics intends to study the Earth system as a whole, looking at the possible couplings among the different geo-layers, i.e., from the earth’s interior to the above atmosphere. It uses specific universal tools to integrate different methods that can be applied to multi-parameter data, often taken on different platforms (e.g., ground, marine or satellite observations). Its main objective is to understand the particular phenomenon of interest from a holistic point of view. Central is the use of entropy, together with other physical quantities that will be introduced case by case. In this paper, we will deal with earthquakes, as final part of a long-term chain of processes involving, not only the interaction between different components of the Earth’s interior but also the coupling of the solid earth with the above neutral or ionized atmosphere, and finally culminating with the main rupture along the fault of concern. Particular emphasis will be given to some Italian seismic sequences.

scholarly journals The mechanical advantage of the magnetosphere: solar-wind-related forces in the magnetosphere-ionosphere-Earth system

2007 ◽  
Vol 25 (1) ◽  
pp. 255-269 ◽  
Author(s):  
V. M. Vasyliūnas
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Lorentz Force ◽  
Linear Momentum ◽  
Neutral Atmosphere ◽  
Earth System ◽  
Mechanical Advantage ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior

Abstract. Magnetosphere-ionosphere interactions involve electric currents that circulate between the two regions; the associated Lorentz forces, existing in both regions as matched opposite pairs, are generally viewed as the primary mechanism by which linear momentum, derived ultimately from solar wind flow, is transferred from the magnetosphere to the ionosphere, where it is further transferred by collisions to the neutral atmosphere. For a given total amount of current, however, the total force is proportional to ℒB and in general, since ℒ2B~ constant by flux conservation, is much larger in the ionosphere than in the magnetosphere (ℒ = effective length, B = magnetic field). The magnetosphere may be described as possesing a mechanical advantage: the Lorentz force in it is coupled with a Lorentz force in the ionosphere that has been amplified by a factor given approximately by the square root of magnetic field magnitude ratio (~20 to 40 on field lines connected to the outer magnetosphere). The linear momentum transferred to the ionosphere (and thence to the atmosphere) as the result of magnetic stresses applied by the magnetosphere can thus be much larger than the momentum supplied by the solar wind through tangential stress. The added linear momentum comes from within the Earth, extracted by the Lorentz force on currents that arise as a consequence of magnetic perturbation fields from the ionosphere (specifically, the shielding currents within the Earth that keep out the time-varying external fields). This implies at once that Fukushima's theorem on the vanishing of ground-level magnetic perturbations cannot be fully applicable, a conclusion confirmed by re-examining the assumptions from which the theorem is derived. To balance the inferred Lorentz force within the Earth's interior, there must exist an antisunward mechanical stress there, only a small part of which is the acceleration of the entire Earth system by the net force exerted on it by the solar wind. The solar-wind interaction can thus give rise to internal forces, significantly larger than the force exerted by the solar wind itself, between the ionosphere and the neutral atmosphere as well as within the current-carrying regions of the Earth's interior.

XXII. Researches in terrestrial physics.-Part II

1851 ◽  
Vol 141 ◽  
pp. 511-547
Keyword(s):  
Physical Properties ◽  
Crystalline State ◽  
Fundamental Importance ◽  
Interior Structure ◽  
Geological History ◽  
Experimental Knowledge ◽  
Physical Evidence ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior

In the first part of these researches, I have endeavoured, by generalizing the hypothesis on which is usually founded the theory of the earth’s figure, not only to improve that theory, but also to establish a secure basis for researches into the changes which may have taken place within and at the surface of the earth during the epochs of its geological history. Although I stated that no precise physical evidence could be adduced for the examination of the assumption that the molecules of the primitive fluid, supposed to have constituted the earth, retained their positions after solidification, it yet appears that such evidence exists, if we may be permitted to draw any conclusions relative to the physical properties of substances in the earth’s interior, from the observed physical properties of substances at its surface. Professor Bischof of Bonn, has shown that Granite contracts in volume in passing from the fluid to the solid crystalline state, from 1 to ⋅7481, Trachyte from 1 to ⋅8187, and Basalt from 1 to ⋅8960. The first of these rocks appears, as far as can be observed, to constitute the greater part of the earth; hence the assumption alluded to must be considered not only as superfluous, but as erroneous. In this Part it is my object to discover relations between the interior structure of the earth and phenomena observed at its surface, and also the effects of the reaction of the fluid nucleus, described in Article 6, Part I., upon the solid crust. I divide this Part into sections, each containing a distinct investigation, the order of arrangement of these sections being determined according to their fundamental importance. The statement of the geological results capable of being deduced from these investigations is, for greater clearness, reserved for the end. Such of these results as chiefly depend on the validity of the reasonings used in Section III. are presented with some diffidence, owing to the imperfect experimental knowledge we possess respecting the subjects discussed in that section. The diminution of the earth’s mean radius by refrigeration is neglected all through, except where the contrary is specially mentioned.

L'interpretation petrographique des donnees geophysiques sur la structure de l'ecorce terrestre

1960 ◽  
Vol S7-II (6) ◽  
pp. 801-820
Author(s):  
G. D. Afanasev
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Oceanic Crust ◽  
Physical State ◽  
Elastic Wave Propagation ◽  
Seismic Velocities ◽  
Petrographic Composition ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior

Abstract The results of recent studies of elastic wave propagation within the earth are reviewed and different interpretations of the earth's interior which have been proposed, particularly in recent American works, are outlined. The results of these studies and of oceanographic work are incompatible with certain classic theories. The main facts are the differences between the continental and oceanic crust and the relatively recent (Tertiary and Quaternary) age of the great zones of continental subsidence, where a transformation from a continental to an oceanic-type crust is implied. The concept of permanent ocean basins is rejected. Differences between the continental and oceanic crust are considered essentially a function of physical state rather than petrographic composition. Continental zones that have subsided are characterized by greater seismic velocities because of the extra pressure to which they have been subjected in the course of the ages.

Earth Heat and Lunar Gravity Geothermal And Tidal Energy

2016 ◽  
Author(s):  
Michael B. McElroy
Keyword(s):  
Natural Gas ◽  
Tidal Energy ◽  
Current Status ◽  
Internal Source ◽  
The Sun ◽  
Radioactive Elements ◽  
The Earth ◽  
Tectonically Active ◽  
Earth’S Interior ◽  
Earth's Interior

To this point, we have discussed the current status and future prospects of energy from coal, oil, natural gas, nuclear, wind, solar, and hydro. With the exception of the contribution from nuclear, the ultimate origin of the energy for all of these sources is the sun— energy captured millions of years ago by photosynthesis in the case of the fossil fuels (coal, oil, and natural gas), energy harvested from contemporary inputs in the case of wind and solar. We turn now to a discussion of the potential for generation of electricity from geothermal sources and ocean tides. Decay of radioactive elements in the Earth’s interior provides the dominant source for the former; energy extracted from the gravitational interaction of the Earth and moon is the primary source for the latter. There are two main contributions to the energy reaching the surface from the Earth’s interior. The first involves convection and conduction of heat from the mantle and core. The second reflects the contribution from decay of radioactive elements in the crust, notably uranium, thorium, and potassium. The composite geothermal source, averaged over the Earth, amounts to about 8 × 10– 2 W m– 2, approximately 3,000 times less than the energy absorbed from the sun. As a consequence of the presence of the internal source, temperatures increase at an average rate of about 25°C per kilometer as a function of depth below the Earth’s surface. The rate of increase is greater in regions that are tectonically active, notably in the western United States and in the region surrounding the Pacific Ocean (the so- called Ring of Fire) — less in others. Of particular interest in terms of harvesting the internal energy source to produce electricity are hydrothermal reservoirs, subsurface environments characterized by the presence of significant quantities of high- temperature water formed by exposure to lava or through contact with unusually hot crustal material. The water contained in hydrothermal reservoirs is supplied for the most part by percolation from the surface through overlying porous rock. The conditions required for production of these hydrothermal systems are relatively specialized.

scholarly journals XXVII. On the rigidity of the earth

1863 ◽  
Vol 153 ◽  
pp. 573-582 ◽  
Keyword(s):  
Physical Condition ◽  
Mathematical Analysis ◽  
Thin Shell ◽  
Liquid Mass ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior ◽  
Rotatory Motion

1. That the earth cannot, as many geologists suppose, be a liquid mass enclosed in only a thin shell of solidified matter, is demonstrated by the phenomena of precession and nutation. Mr. Hopkins, to whom is due the grand idea of thus learning the physical condition of the interior from phenomena of rotatory motion presented by the surface, applied mathematical analysis to investigate the rotation of rigid ellipsoidal shells enclosing liquids, and arrived at the conclusion that the solid crust of the earth must be not less than 800 or 1000 miles thick. Although the mathematical part of the investigation might be objected to, I have not been able to perceive any force in the arguments by which this conclusion has been controverted, and I am happy to find my opinion in this respect confirmed by so eminent an authority as Archdeacon Pratt. 2. It has always appeared to me, indeed, that Mr. Hopkins might have pressed his argument further, and have concluded that no continuous liquid vesicle at all approaching to the dimensions of a spheroid 6000 miles in diameter can possibly exist in the earth’s interior without rendering the phenomena of precession and nutation very sensibly different from what they are.

Review Lecture: Experiment and the crust of the Earth

1968 ◽  
Vol 307 (1491) ◽  
pp. 373-389
Keyword(s):  
Earth Science ◽  
The Earth ◽  
Earth’S Interior ◽  
Earth's Interior ◽  
Lecture Experiment

In this review I should like to consider our progress in unravelling some problems in Earth science, particularly problems where experiment has led to a much deeper understanding of observations concerning the formation of rocks now found at the surface of the Earth. While geophysical probes into the Earth’s interior become increasingly sophisticated, I think it is still true that most of our models of Earth properties and materials at depth, are based on observations and experiments on materials seen at the surface if we include meteorites in the sample. It is also true that crustal phenomena provide most of the evidence concerning the dynamics and evolution of the entire Earth.

scholarly journals On the Ellipsoidal Distribution of Density in the Earth's Interior

1980 ◽  
Vol 78 ◽  
pp. 159-159
Author(s):  
G. A. Mescheryakov ◽  
Y. P. Dejneka
Keyword(s):  
Fourier Series ◽  
Free Oscillations ◽  
Maximum Difference ◽  
Fourth Degree ◽  
Generalized Fourier Series ◽  
The Earth ◽  
Seismological Data ◽  
Earth’S Interior ◽  
Earth's Interior

Density within the Earth is expressed by means of generalized Fourier series as a function of the coordinates of a point: its distance from the geocenter, colatitude, and longitude. The following data are used to obtain the coefficients of the series: the parameters of the Earth ellipsoid (assumed to be biaxial), the dynamical flattening of the Earth, the Stokes constants, and the density jumps at four surfaces according to seismological data.The model of the Earth proposed by the authors is composed of five layers, the density in each layer being expressed as a function of the distance from the center of the Earth by a polynomial of fourth degree. To verify the model, periods of the fundamental modes of spherical and torsion oscillations are derived and compared with observations of the free oscillations of the Earth. The maximum difference is within the errors of the observed periods.

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