scholarly journals 3.7 Predicted Favorable Visibility Conditions for Anomalous Tails of Comets

1976 ◽  
Vol 31 ◽  
pp. 339-342
Author(s):  
Zdenek Sekanina
Keyword(s):  
Production Rate ◽  
Nodal Line ◽  
Dust Particles ◽  
Two Dimensional ◽  
Orbit Plane ◽  
Geometric Conditions ◽  
The Earth ◽  
Physical Presence

It was shown elsewhere (Sekanina, 1974) that the observability from the earth of an anomalous tail (antitail) of a comet can be rather straightforwardly predicted from the dynamical and geometric conditions. The physical presence or absence of the antitail at a precalculated time is then a measure of the comet’s production rate, at the relevant emission times, of relatively heavy dust particles (mostly of submillimeter size) that constitute such an antitail. Because the large grains are e-mitted from the nucleus at very low velocities (typically meters or tens of meters per second), an antitail is essentially a two-dimensional formation in the orbit plane of the comet and can be recognized best when projected edge-on, i.e., when the earth crosses the nodal line of the comet’s orbit. In general, however, this condition is not essential for the recognition of antitails (cf., e.g., Comet Kohoutek 1973 XII).

Neubestimmung der natürlichen irdischen Tritiumzerfallsrate und die Frage der Herkunft des „natürlichen“ Tritium

1959 ◽  
Vol 14 (4) ◽  
pp. 334-342 ◽  
Author(s):  
F. Begemann
Keyword(s):  
Phase Shift ◽  
Decay Rate ◽  
Production Rate ◽  
Residence Time ◽  
Cosmic Radiation ◽  
Sunspot Cycle ◽  
Energy Component ◽  
Tritium Content ◽  
The Earth ◽  
Snow Samples

The terrestrial decay rate of “natural” tritium has been re-determined from measurements of the tritium content of old snow samples from Greenland. The finding by CRAIG and BEGEMANN and LIBBY has been confirmed that the tritium decay rate is about 10 times higher than was anticipated previously.Two mechanisms to explain the discrepancy are discussed,a) production by the low energy component of the cosmic radiation andb) the accretion of solar tritium by the earth, as suggested by FELD and ARNOLD.It is shown that in case all the tritium is produced by cosmic radiation the tropospheric production rate may be expected to vary in antiphase with the sunspot cycle, whereas in case of accretion of solar tritium by the earth the variation should be in phase with the sunspot cycle. In both cases a phase shift between the stratospheric production rate and the amount of tropospheric tritium is to be expected because of the residence time of tritium in the stratosphere. A measurement of the phase shift should allow to determine this residence time.The data obtained on the Greenland samples appear to show such a variation of the production rate. The results can be explained best by assuming that all the tritium is produced by cosmic radiation. This result, however, is only preliminary. More systematic measurements are required to decide between the two possibilities.

Statistical properties of Rayleigh waves due to scattering by topography

1967 ◽  
Vol 57 (1) ◽  
pp. 83-90
Author(s):  
J. A. Hudson ◽  
L. Knopoff
Keyword(s):  
Surface Waves ◽  
Rayleigh Waves ◽  
Seismic Noise ◽  
Forward Scattering ◽  
Statistical Properties ◽  
Body Waves ◽  
Simplified Model ◽  
Two Dimensional ◽  
Especial Reference ◽  
The Earth

abstract The two-dimensional problems of the scattering of harmonic body waves and Rayleigh waves by topographic irregularities in the surface of a simplified model of the earth are considered with especial reference to the processes of P-R, SV-R and R-R scattering. The topography is assumed to have certain statistical properties; the scattered surface waves also have describable statistical properties. The results obtained show that the maximum scattered seismic noise is in the range of wavelengths of the order of the lateral dimensions of the topography. The process SV-R is maximized over a broader band of wavelengths than the process P-R and thus the former may be more difficult to remove by selective filtering. An investigation of the process R-R shows that backscattering is much more important than forward scattering and hence topography beyond the array must be taken into account.

Squaring the Circle

2020 ◽  
pp. 51-82
Author(s):  
Ciaran McMorran
Keyword(s):  
James Joyce ◽  
Euclidean Geometry ◽  
Natural World ◽  
Curved Surfaces ◽  
Two Dimensional ◽  
Natural Phenomena ◽  
Visual Objects ◽  
Squaring The Circle ◽  
The Earth ◽  
Geometric Objects

This chapter highlights the practical and metaphysical issues which James Joyce associates with the application of Euclidean geometry as a geo-meter (a measure of the Earth) in “Ithaca.” It demonstrates how the “mathematical catechism” of “Ithaca” geometrizes the visible world, translating natural phenomena into their ideal Euclidean equivalents. In a topographical context, it illustrates how variably curved surfaces undergo a process of rectification as they are mediated by the catechetical narrative, and how this leads to a confusion between maps and their territories. In light of the narrative’s conceptualization of Molly Bloom as both a human and a heavenly body, this chapter also examines the mythical notions which originate from the mathematical catechism’s conflation of geometric objects and the visible world. By evoking an incongruity between visual objects and their meters, it argues, Joyce explores the possible limits of squaring the circle, both topographically (in terms of projecting a curved natural surface onto a two-dimensional map, as in Mercator’s projection) and figuratively (in the sense that the irregularly curved features of the natural world are rectified as they are represented textually on a rectilinear page).

scholarly journals Amplitude of Sunspot-Dependent Radiocarbon Variations: Data from Corals and Wine

Radiocarbon ◽  
1985 ◽  
Vol 27 (1) ◽  
pp. 111-115
Author(s):  
Mordeckai Magaritz ◽  
Israel Carmi ◽  
Ziv Sirkes
Keyword(s):  
Theoretical Analysis ◽  
Theoretical Calculation ◽  
Production Rate ◽  
Sunspot Cycle ◽  
Published Data ◽  
Earth Surface ◽  
The Earth ◽  
Surface System ◽  
Experimental Values

It has been suggested that the sunspot cycle modulates the production rate of radionuclides in the atmosphere and that these modulations can be traced in various parts of the earth surface system. On the basis of a theoretical analysis, Damon, Sternberg, and Radnell (1983) have concluded that the effects of the 11-yr cycle of sunspots should be observable in 14C data provided the measurements are done at a 2 permil (sd) level. This conclusion is based on calculations using models discussed by Lingenfelter and Ramaty (1970) and by O'Brien (1979) and on the 14C inventory modified from Damon, Lerman, and Long (1978). In this note we compare the amplitude estimate of Damon, Sternberg, and Radnell (1983), who calculated a representative peak-to-peak variation of 1.7‰ in 14C for the sunspot cycle between 1848 and 1856, with experimental values derived from recently published data. We find the experimental value to be larger by a significant factor from the theoretical calculation.

THREE‐DIMENSIONAL INDUCED POLARIZATION AND ELECTROMAGNETIC MODELING

Geophysics ◽  
1975 ◽  
Vol 40 (2) ◽  
pp. 309-324 ◽  
Author(s):  
Gerald W. Hohmann
Keyword(s):  
Integral Equation ◽  
Green's Functions ◽  
Green’S Functions ◽  
Three Dimensional ◽  
Induced Polarization ◽  
The Body ◽  
Scale Model ◽  
Two Dimensional ◽  
Electromagnetic Modeling ◽  
The Earth

The induced polarization (IP) and electromagnetic (EM) responses of a three‐dimensional body in the earth can be calculated using an integral equation solution. The problem is formulated by replacing the body by a volume of polarization or scattering current. The integral equation is reduced to a matrix equation, which is solved numerically for the electric field in the body. Then the electric and magnetic fields outside the inhomogeneity can be found by integrating the appropriate dyadic Green’s functions over the scattering current. Because half‐space Green’s functions are used, it is only necessary to solve for scattering currents in the body—not throughout the earth. Numerical results for a number of practical cases show, for example, that for moderate conductivity contrasts the dipole‐dipole IP response of a body five units in strike length approximates that of a two‐dimensional body. Moving an IP line off the center of a body produces an effect similar to that of increasing the depth. IP response varies significantly with conductivity contrast; the peak response occurs at higher contrasts for two‐dimensional bodies than for bodies of limited length. Very conductive bodies can produce negative IP response due to EM induction. An electrically polarizable body produces a small magnetic field, so that it is possible to measure IP with a sensitive magnetometer. Calculations show that horizontal loop EM response is enhanced when the background resistivity in the earth is reduced, thus confirming scale model results.

Anthropogenic Heat Release Into the Environment

2012 ◽  
Author(s):  
Kaufui V. Wong ◽  
Yading Dai ◽  
Brian Paul
Keyword(s):  
Climate Change ◽  
Solar Radiation ◽  
Production Rate ◽  
Heat Production ◽  
Domestic Animals ◽  
Anthropogenic Heat ◽  
Net Energy ◽  
The Earth ◽  
Heat Production Rate ◽  
Energy Dissipated

This work is intended to systematically study an inventory of the anthropogenic heat produced. This research strives to present a better estimate of the energy generated by humans and human activities, and compare this estimate to the significant energy quantity with respect to climate change. Because the Top of Atmosphere (TOA) net energy flux was found to be 0.85±0.15 W/m2 the planet is out of energy balance, as studied by the group from NASA in 2005. The Earth is estimated to gain 431 TW from this energy imbalance. This number is the significant heat quantity to consider when studying global climate change, and not the 78,300 TW, the absorbed part of the primary solar radiation reaching the Earth’s surface, as commonly cited and used at present in the literature. Based on energy supplied to the boilers (in the Rankine cycle) of at least 13 TW, body energy dissipated by 7 billion people and their domestic animals, the value of the total world anthropogenic heat production rate is 15.26 TW or 3.5% of the energy gain by the Earth. Based on world energy consumption and the energy dissipated by 7 billion people and their domestic animals, the value of the total world anthropogenic heat production rate is 19.7 TW or about 5% of the energy gain by the Earth. These numbers are significantly different from 13 TW. More importantly, the figures are 3.5 to 5% of the net energy gained by the Earth, and hence significant. The quantity is not 0.017% of the absorbed part of the main solar radiation reaching the Earth’s surface and negligible.

scholarly journals Interaction of Lunar Ejecta and the Magnetosphere of the Earth

1980 ◽  
Vol 90 ◽  
pp. 425-428
Author(s):  
W. M. Alexander ◽  
J. D. Corbin
Keyword(s):  
Initial Study ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Lunar Phases ◽  
Gravitational Forces ◽  
The Earth ◽  
Significant Flux

A significant flux of ejecta from lunar impacts of interplanetary dust particles leaves selenocentric space and enters the magnetosphere of the earth. During favorable lunar phases, 80% of the ejecta enter the magnetosphere where their orbits are determined by electrodynamic as well as gravitational forces. Initial study of the orbital characteristics and perturbations of these magnetosphere ejecta is presented and its implications are discussed.

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