The Theoretical Description of the Nutation of the Earth

1981 ◽  
pp. 103-110 ◽  
Author(s):  
Martin L. Smith
Keyword(s):  
Theoretical Description ◽  
The Earth

Modeling ELF waves in the non-uniform Earth-ionosphere cavity

2021 ◽  
Author(s):  
Tamas Bozoki ◽  
Erno Pracser ◽  
Gabriella Satori ◽  
Andrzej Kulak ◽  
Janusz Mlynarczyk ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Numerical Solutions ◽  
Model Development ◽  
Resonance Field ◽  
Low Frequency ◽  
Relative Difference ◽  
Telegraph Equation ◽  
Theoretical Description ◽  
Inversion Algorithm ◽  
The Earth

<p>Below 100 Hz, in the lowest part of the extremely low frequency (ELF, 3 Hz - 3 kHz) band lightning-radiated electromagnetic waves propagate with extremely low attenuation (roughly below 1 dB/Mm) within the Earth-ionosphere waveguide which makes possible the formation of global electromagnetic resonances, known as Schumann resonances (SRs). The most commonly used description of this resonance field assumes a uniform Earth-ionosphere cavity, i.e. that the propagation conditions for ELF waves are practically the same on the dayside and nightside hemispheres, which is the most vulnerable simplification of these models. </p><p>In this work we present two different forward models for SRs that take into consideration the day-night asymmetry of the Earth-ionosphere cavity and are based on the analytical and numerical solutions of the two-dimensional telegraph equation (TDTE). We present numerical tests showing that the two models produce practically the same output, i.e. the relative difference between them is less than 0.4%. The conspicuous conformity between the outputs establishes not only the correctness of the formalisms but the correctness of the implementations (the coding) as well. To the best of the authors’ knowledge this is the first work that verifies this conformity between the two independent solutions. </p><p>We also compare our stationary models with time-dependent solutions of the TDTE as the stationarity of the resonance field may represent the next most vulnerable simplification that needs to be dismissed to approach a more realistic theoretical description of SRs. All these steps in model development serve our aim to infer global lightning activity based on multi-station ELF measurements by applying a sophisticated inversion algorithm.</p>

scholarly journals The Theoretical Description of the Nutation of the Earth

1980 ◽  
Vol 56 ◽  
pp. 103-110
Author(s):  
Martin L. Smith
Keyword(s):  
Theoretical Description ◽  
Conventional Wisdom ◽  
The Earth ◽  
Points Of View

This talk was intended, I think, to be an opportunity to recite the conventional wisdom of the class of geophysicists who are interested in investigating theoretically the Earth’s wobble and nutation. It has become clear since the Kiev meeting in 1977, however, that we have not yet agreed upon the contents of our conventional wisdom and it would be premature, and presumptuous, of me to pretend to recite it. What I can do is to tell you what I think the conventional wisdom ought to be. In doing so I shall give free rein to my prejudices and little consideration to opposing points of view (they must speak for themselves). Nothing in this talk is noticeably original; virtually all of it is extracted from the work of others or from the folklore of this topic.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

Probable Structure and Nature of the Formations on the Reverse Side of the Moon According to Photometric Measurements of Lunar Photographs

1962 ◽  
Vol 14 ◽  
pp. 39-44
Author(s):  
A. V. Markov
Keyword(s):  
The Moon ◽  
Probable Structure ◽  
The Earth ◽  
Interplanetary Station ◽  
Photometric Measurements ◽  
Automatic Interplanetary Station

Notwithstanding the fact that a number of defects and distortions, introduced in transmission of the images of the latter to the Earth, mar the negatives of the reverse side of the Moon, indirectly obtained on 7 October 1959 by the automatic interplanetary station (AIS), it was possible to use the photometric measurements of the secondary (terrestrial) positives of the reverse side of the Moon in the experiment of the first comparison of the characteristics of the surfaces of the visible and invisible hemispheres of the Moon.

Seti Space Missions

1997 ◽  
Vol 161 ◽  
pp. 761-776 ◽  
Author(s):  
Claudio Maccone
Keyword(s):  
Electromagnetic Waves ◽  
Space Missions ◽  
Gravitational Lens ◽  
The Sun ◽  
Space Antenna ◽  
Focal Distance ◽  
Large Space ◽  
The Earth ◽  
Space Antennas ◽  
New Space

AbstractSETI from space is currently envisaged in three ways: i) by large space antennas orbiting the Earth that could be used for both VLBI and SETI (VSOP and RadioAstron missions), ii) by a radiotelescope inside the Saha far side Moon crater and an Earth-link antenna on the Mare Smythii near side plain. Such SETIMOON mission would require no astronaut work since a Tether, deployed in Moon orbit until the two antennas landed softly, would also be the cable connecting them. Alternatively, a data relay satellite orbiting the Earth-Moon Lagrangian pointL2would avoid the Earthlink antenna, iii) by a large space antenna put at the foci of the Sun gravitational lens: 1) for electromagnetic waves, the minimal focal distance is 550 Astronomical Units (AU) or 14 times beyond Pluto. One could use the huge radio magnifications of sources aligned to the Sun and spacecraft; 2) for gravitational waves and neutrinos, the focus lies between 22.45 and 29.59 AU (Uranus and Neptune orbits), with a flight time of less than 30 years. Two new space missions, of SETI interest if ET’s use neutrinos for communications, are proposed.

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