Time elements in rectangular coordinates

In a paper by the second author (Nacozy, 1981), various time elements are presented for use with the Sundman time transformation. In that paper, the time elements are given in terms of Keplerianorbital elements. We give here the corresponding time elements in terms ofrectangular coordinates. Extensive references are given in the previous paper and will be omitted here.We present additional numerical experiments comparing the use of time elementsand time transformationstogether with the use of time transformationsalone. The results indicate a reduction in computational error when time elements are used.     

A new sequence of international latitude service pole coordinates and the secular polar motion

From individual ILS data in a homogeneous system, we derived a new sequence of the coordinates of the pole. This was then used in an analysis of the secular polar motion. We found: 1) At a confidence level of 95%, the linear drift of the ILS mean pole over the last 80 years is along 63° 3 longitude West, at an average speed of 0″.00305/yr. 2) The libration of the mean pole is rather regular, with a prominent term of about 30 yr, and detectable terms of 18.6 yr and 9.3 yr. 3) Station Ukiah is drifting northwards at a speed of 0″.00276/yr, while all the other stations are quite stable. Hence the ILS data cannot be taken as showing an anti-clockwise rotation of the Pacific coast at present.     

Rotation of the magnetic elements in polar regions on the Sun

Using the Michelson Doppler Imager (MDI) data from Solar and Heliospheric Observatory (SOHO), the rotation rate of the unipolar magnetic regions in North high-latitude regions of the Sun is estimated by tracking individual magnetic elements. The analysis reveals a strong spin down near the pole, which is greater than the Doppler and magnetic rotation rates estimated by Snodgrass & Ulrich (1990), and rotation rate inferred from helioseismology (Birch & Kosovichev 1998), and is probably related to variation of velocity gradient in the subsurface shear layer. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comparison between the polar coordinates determined by different observational techniques

The main characteristics of several polar coordinate systems in present use are compared. The systematic differences between the classical technique (BIH 68) and the new technique (DMA and IASOM) are analysed in depth and their external errors estimated.     

Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006

Every three years the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the directions of the poles of rotation and the prime meridians of the planets, satellites, minor planets, and comets. This report introduces improved values for the pole and rotation rate of Pluto, Charon, and Phoebe, the pole of Jupiter, the sizes and shapes of Saturn satellites and Charon, and the poles, rotation rates, and sizes of some minor planets and comets. A high precision realization for the pole and rotation rate of the Moon is provided. The expression for the Sun’s rotation has been changed to be consistent with the planets and to account for light travel time     

Proton energy deposition in molecular and atomic oxygen and applications to the polar cap

We extend the microscopic approach developed for proton energy deposition in N₂ to the general case of proton bombardment of a polar atmosphere composed of N₂, O₂ and O. We calculate the volume emission rates of various N₂⁺, O₂, O₂⁺ and OI emissions that would be encountered in a typical PCA event. Our results demonstrate that the ratios of $\text{I}\text{(5577)}\text{I}\text{(3914)}$ and $\text{I}\text{(6300)}\text{I}\text{(3914)}$ are strongly depe spectra considered.     

High-precision stellar abundances of the elements: methods and applications

Efficient spectrographs at large telescopes have made it possible to obtain high-resolution spectra of stars with high signal-to-noise ratio and advances in model atmosphere analyses have enabled estimates of high-precision differential abundances of the elements from these spectra, i.e. with errors in the range 0.01–0.03 dex for F, G, and K stars. Methods to determine such high-precision abundances together with precise values of effective temperatures and surface gravities from equivalent widths of spectral lines or by spectrum synthesis techniques are outlined, and effects on abundance determinations from using a 3D non-LTE analysis instead of a classical 1D LTE analysis are considered. The determination of high-precision stellar abundances of the elements has led to the discovery of unexpected phenomena and relations with important bearings on the astrophysics of galaxies, stars, and planets, i.e. (i) Existence of discrete stellar populations within each of the main Galactic components (disk, halo, and bulge) providing new constraints on models for the formation of the Milky Way. (ii) Differences in the relation between abundances and elemental condensation temperature for the Sun and solar twins suggesting dust-cleansing effects in proto-planetary disks and/or engulfment of planets by stars; (iii) Differences in chemical composition between binary star components and between members of open or globular clusters showing that star- and cluster-formation processes are more complicated than previously thought; (iv) Tight relations between some abundance ratios and age for solar-like stars providing new constraints on nucleosynthesis and Galactic chemical evolution models as well as the composition of terrestrial exoplanets. We conclude that if stellar abundances with precisions of 0.01–0.03 dex can be achieved in studies of more distant stars and stars on the giant and supergiant branches, many more interesting future applications, of great relevance to stellar and galaxy evolution, are probable. Hence, in planning abundance surveys, it is important to carefully balance the need for large samples of stars against the spectral resolution and signal-to-noise ratio needed to obtain high-precision abundances. Furthermore, it is an advantage to work differentially on stars with similar atmospheric parameters, because then a simple 1D LTE analysis of stellar spectra may be sufficient. However, when determining high-precision absolute abundances or differential abundance between stars having more widely different parameters, e.g. metal-poor stars compared to the Sun or giants to dwarfs, then 3D non-LTE effects must be taken into account.     

Optimal set of photometric elements of the eclipsing variable TZ Bootis

The eclipsing system of W UMa-type TZ Bootis has been examined on the basis of six light curves analyzed by the means of the Fourier techniques. An optimal resulting set of geometric elements for the system is obtained from both minima, through there magnitudes variations during the periods 1967, 1969, 1974, 1976, 1978, and 1980.The intrinsic variability of the system has been discussed in the light of the behaviour of the light curves.     

System of selenodetic coordinates based on heliometric observations of the Moon at Kazan

On the basis of heliometric observations of the Moon carried out by the author between 1969–1975 a system of the coordinates of 32 lunar craters has been set up which is independent of the scale and orientation. The zero point of these coordinates has been fixed by the position of the crater Mösting A in accordance with Koziel (1967a, b; 1970).     

Non-axisymmetric magnetostatic equilibrium in cylindrical coordinates and its application to sunspots

This paper describes a general solution to the 3-dimensional, 2-component mangetostatic equation assuming the total pressure (gas plus magnetic) to be a function of the height only. By adjusting the two arbitrary functions appearing in the general solution one may obtain various particular solutions which are not subject to the assumption of perturbations being small when applied to solar phenomena. One such particular solution qualitatively accounts for the observed asymmetry in the shape of the sunspots and the filimentary structure in them.     

Report of the IAU/IAG/COSPAR working group on cartographic coordinates and rotational elements of the planets and satellites: 1991

Every three years the IAU/IAG/COSPAR Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites revises tables giving the directions of the north poles of rotation and the prime meridians of the planets and satellites. Also presented are revised tables giving their sizes and shapes.     

A snapshot of the polar ionosphere

This paper presents a picture of the north polar F layer and topside ionosphere obtained primarily from three satellites (Alouette 2, ISIS 1, ISIS 2), that passed over the region within a time interval of ca. 50 min on 25 April 1971, a magnetically quiet day. The horizontal distribution of electron densities at the peak of the F layer is found to be similar to synoptic results from the IGY. Energetic particle and ionospheric plasma data are also presented, and the F layer data are discussed in terms of these measurements, and also in terms of electric field and neutral N₂ density measurements made by other satellites on other occasions. The major features observed are as follows: A tongue of F region ionization extends from the dayside across the polar cap, which is accounted for by antisunward drift due to magnetospheric convection. In the F layer and topside ionosphere, the main effect of auroral precipitation appears to be heating and expansion of the topside. A region of low F layer density appears on the morning side of the polar cap, which may be due to convection and possibly also to enhanced N₂ densities.     

The relative age of the escarpments in the Martian polar laminated terrain based on morphology

Three theories have been proposed to explain the morphology of large-scale topographic features seen in the Martian polar laminated terrain. These features, which are subcircular in planimetric form, appear as dark bands in wide-angle Mariner 9 frames of the polar cap. Two of the theories (by Sagan and Murray) suggest that the features are constructional, built up through deformation of thick CO₂ layers or built through localized deposition of ice and dust. Another theory (Cutts) suggests the features are channels and escarpments cut into a pre-existing, featureless, layered plateau. The constructional theories suggest that the features were formed sequentially while the erosive theory suggests formation was more or less simultaneous. An experiment was performed to test whether it was possible to discern the relative age of the features.It was assumed that if the features are constructional, continued exposure to erosional processes would change their planimetric form with time. Murray has postulated which features are oldest and which are youngest. It was found, however, that the supposed oldest features were statistically neither significantly more nor less irregular than the supposed youngest escarpments.This evidence has led to the conclusion that the features were probably carved nearly simultaneously into a previously deposited, featureless, stratified plateau rather than being constructed sequentially.     

A FORTRAN-based Poisson series processor and its applications in celestial mechanics

The present article describes the design and applications of our Poisson series subroutine package developed and maintained since 1968. The programs are written in standard FORTRAN-77 and are almost independent of the wordlength of the particular computer. The system has no restriction on the number of polynomial and angular variables and the storage allocations are completely automatic, invisible to the user.The nucleus of the system consists of about 20 basic traffic subroutines that handle the terms of the different series. Besides these subroutines, we have a number of I/O routines as well as arithmetic subroutines and a large number of Celestial Mechanics applications such as the classical expansions of the Kepler Problem and several expansions of Disturbing Functions. A preprocessor has also been built, allowing the user to write code in a high-level language, such as Jefferys' Trigman, and then translate it in our call-statements.The system was developed on several different computers: first on the Univac 1108 at the Jet Propulsion Laboratory in 1968, then the IBM 360-91 at UCLA, Los Angeles, California and finally the CDC 6600 and CYBER 170/750 at the University of Texas, Austin, Texas. The latest version is entirely geared towards the IBM-PC and compatibles.     

Possible role of brines in the darkening and flow-like features on the Martian polar dunes based on HiRISE images

This work identifies and describes features of the changing seasonal frost-covered surface of Mars based on HiRISE images, and analyses the possibility that ephemeral liquid brine formation produces them. Because some of these dark features show flow-like appearance, and salts on Mars are present, liquid brines might be also present, possibly accounting for the changing droplet-like features on the Phoenix lander.We observed in-situ darkening and movement of dark features (or movement of the darkening front) on seasonal frost-covered polar dunes. Darkening and brightening may happen within several meters from each other during local spring. Darkening always starts from the bottom and moves up, while brightening progresses from top and moves toward the bottom between the small dune ripples. Brightening occurs during the springtime warming on time scales of several days close to the sites of darkening; therefore, dark material falling from the air, and refreezing of bright ice on it, does not adequately explain the observations. Interpreting the observations as brine-related melting or refreezing also poses problems, but because brine may engulf salt grains or ice blocks, phase changes here could be influenced by factors other than temperature values, and could produce the observations.Analysis of absolute albedo changes indicates that the flow-like features are the darkest at their lower frontal end, sometimes darker than the dark spot from which they originate. A bright halo (white collar) also forms around these spots, possibly due to refreezing. Inside the observed larger spots an outer gray area surrounds the central darkest cores, which is about 10 cm lower than the surrounding bright CO₂ ice. At those places, most or all of the CO₂ ice deposited earlier has disappeared, and H₂O ice is present. Observations of dark flow features moving on the top of this H₂O rich layer suggest even if the flow features start as dry dune avalanches of rolling grains, their dark material heated by solar insolation is in contact with H₂O ice and may produce brines.     

New set of geometrical and physical elements of the two variable stars SW lacertae and OO aquilae

Photoelectric observations of the two eclipsingvariables, were obtained in UBV standard system, for SWLac and, inVB standard system for OOAql.A new set of geometrical and physical elements for thesystems were obtained from both minima, through theirmagnitude variation during the observation time using themethod of: Fourier Analysis Techniques in-Frequency-domain for thelight curve changes. The two eclipsing variables are contact, the firstcontact angle was 48.1^° for SW Lac and 47.7^° for OO Aql.Absolute elements and effective temperatures of the twocomponents for both systems are derived.     

A separable potential in triaxially ellipsoidal coordinates satisfying the laplace equation

This paper derives the most general potential function which allows separation of the hamilton-Jacobi equation in orthogonal coordinates and which satisfies the Laplace equation. The resulting potential is then specialized to the case of interest for near-Earth satellites, where the proper behavior of the potential at infinity is obtained and singularities in the region of interest are eliminated. The Vinti potential is found as a special case.This paper was prepared under the sponsorship of the Electronics Research Center of the National Aeronautics and Space Administration through NASA Grant NGR-22-009-262.