** **

**CORRELATED
FLUCTUATING SIGNALS IN THE ANALYSIS OF THE LARGE SCALE STRUCTURE OF THE
UNIVERSE**

**DORU MARIAN SURAN, NEDELIA ANTONIA POPESCU**

**Astronomical Institute of the Romanian Academy,**

**75212 Bucharest 28, Romania**

*Abstract*.Recent observations of the Large Scale Structure
of the Universe suggest inhomogeneities on a scale larger than previously
thought. Our previous results (Surqn 1991) indicated that the signals of
the inhomogeneities in different 3D catalogs ( galaxies, clusters, superclusters)
are correlated, suggesting the presence of phase fluctuations in the long
tail of the correlation function (§(r) for r > r*g*). The results
are in good agreement with BEKS (1990, 1991; 1D pencil beams techniques).
The comparison with different 3D simulations is made in order to derive
the cosmological texture of the Universe on a scale lerger than 20 MPC.
Also the comparison with the simulated power spectrum is made in order
to derive the transition function Tf (k) for the intermediate scale (100h-¹

**Mpc< r < 1000 h-¹ Mpc)**

*Key words*: *Large Scale Structure of the Universe*- texture;
*cosmology* - correlation function, transfer function.

** **

**GRAVITATONAL
ENERGY FOR A CLASS OF RELATIVISTIC STELLAR MODELS**

**VASILE URECHE**

**University of Cluj-Napoca, Faculty of Mathematics,**

**Str. M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania**

**TIBERIU OPROIU**

**Astronomical Institute of the Romanian Academy, Astronomical Observatory
Cluj-Napoca**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract*. The paper deals with the determination of the gravitational
energy at barotopic stellar

**models in a relativistic approximaion. The way to calculate the gravitational
packing coefficient is shown. The numerical estimates are tabulated and
plotted. One can conclude that the gravitational energy represents a significant
part of the total stellar energy.**

*Key words*: relativistic stars - barotropic models - gravitational
energy.

** **

**GABRIELA OPRESCU , DORU MARIAN SURAN**

**Astronomical Institute of the Romanian Academy,**

**Str. Cutitul de Argint No. 5, 75212 Bucharest 28, Romania**

*Abstract*. UBV light curves for AW Cam are obtained at Bucharest
Observatory. Light Curves solutions are presented.

*Key words*: *eclipsing binaries* - AW Cam photometry,
elements.

** **

**REMARKS
ON THE APSIDAL MOTION OF TX URSAE MAJORIS**

**IOAN TODORAN and RODICA ROMAN**

**Astronomical Observatory, Cluj-Napoca, Romania**

*Abstract*. The hypothesis of apsidal motion is reviewed and
it is found that only such a phenomenon cannot explain the observed O -
C diagram, for binary system TX Ursae Majoris.

*Key words:* eclipsing binary - apsidal motion: TX UMa.

** **

**CONVECTION IN
THE PRESENCE OF SUNSPOTS**

**VARUJAN V. PAMBUCCIAN**

**University of Bucharest, Department of Mathematics**

*Abstract*. The present paper deals with three dimensinal stationary
convection in the presence of a general weak magnetic field and of a strong
magnetic field generated by a sunspot or a group of sunspots. This strong
magnetic field will drive the entire phenomenon.** **

**THE
GLOBAL ANALYSIS OF TIME DETERMINATIONS MADE IN BUCHAREST DURING 1962 -1989
(II)**

**MAGDA STAVINSCHI, DANA DINESCU, GHEORGHE VASS, ALINA DONEA**

**Astronomical Institute of the Romanian Academy,**

**Cutitul de Argint 5, 75212 Bucharest 28, Romania**

*Abstract*. The first part of this work was presented during
the 7th International Symposium of Geodesy and Geophysics of the Earth
- the IAG No. 122 Symposium - in Potsdam and was published in the Proceedings
of the Symposium (Springer Verlag, in print). Because at the moment of
the Symposium we only had preliminary results of the analysis, in the present
paper a complete image of the data processing and of the results has been
included.

*Key words*: Earth's rotation, Time determination.

** **

**COLLISION AND
NEAR-COLLISION ORBITS IN POST-NEWTONIAN GRAVITATIONAL SYSTEMS**

**GEORGE BALLINGER*, FLORIN N. DIACU****

**Department of Mathematics and Statistics, University of Victoria**

**P.O. Box 3045, Victoria, B.C., Canada, V8W 3P4**

*Abstract*. We study the central force problem involving a particle
of unit mass orbiting a centre while subjected to a post-Newtonian gravitational
force proportional to r-² (1 + __ 1n r), where r is the distance to
the centre and |__|<1. We examine the behaviour of the paricle at and
near collision with the centre. By using McGehee - type transformations
we blow up the singularity at r = 0 and obtain regularized equations of
motion. After proving the collision manifold to be a torus, a qualitative
study of the flow is performed. Collision-ejection solutions are shown
to be block-regularizable. Finally, we draw the conclusion that post-Newtonian
laws of this type, with - 1 < __<0, are similar to the Newtonian
one in the neighbourhood of singularities.

*Key words*: celestial mechanics - post-Newtonian gravitational
law-collisions.** **

**ON THE
CURVATURE OF THE TRAJECTORIES IN THE RESTRICTED PROBLEM OF THREE BODIES**

**MIRA-CRISTIANA ANISIU**

**Institute of Mathematics, Cluj-Napoca**

**Str. Republicii 37, P.O. Box 68, 3400 Cluj-Napoca, Romania**

*Abstract*. It is proved that for the restricted problem of
three bodies there are at most three osculating solutions at one point.
Points were there are three or two osculating solutions specified.

*Key words*: Celestial Mechanics - Restricted Three-Body Problem.

** **

**TWO
- BODY PROBLEM WITH ANISOTROPIC GRAVITATIONAL CONSTANT**

**VASILE MIOC, CRISTINA BLAGA**

**Astronomical Institute of the Romanian Academy**

**Astronomical Observatory Cluj-Napoca**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract.*The two- body problem corresponding to a gravitational
force with anisotropic* G* is treated by means of perturbation theory.
The integration of Newton-Euler equations shows that the perturbed orbit
is of elliptic type, lies in a fixed plane, and its semimajor axis, eccentricity,
and the argument of pericentre, obtained as functions of the argument of
latitude, undergo 2_ periodic variations. The nodal period, determined
with an accuracy of first order in a small parameter___ and third order
in eccentricity, results to be shorter than the corresponding very general
two-body problem with changing equivalent gravitational parameter.

*Key words*: celestial mechanics - equivalent gravitational
parameter - anisotropy of gravitation - orbital motion - perurbation theory.

** **

**NODAL
PERIOD IN MOTION PERTURBED BY A FORCE ACTING IN ORBIT PLANE**

**VASILE MIOC**

**Astronomical Institute of the Romanian Academy**

**Astronomical Observatory Cluj-Napoca**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract*. An analytic estimate (much improved as against the
actual ones) of the nodal period corresponding to an orbit which experiences
perturbations due to a force depending in a small parameter and acting
in the orbit plane is obtained. The case of radial perturbing force is
treated separately. An accuracy of any order in the small parameter and
of a desired order in eccentriciry can be reached. The main formulae are
applicable to various concrete astronomical situations modelable by this
theory.

*Key words*: celestial mechanics - perturbation theory - orbital
motion - nodal period.

** **

**ROMANIAN ASTRONOMICAL JOURNAL, VOL. 3, NO. 2, 1993**

** **

**RELATIVISTIC
ROTATING HOMOGENEOUS STARS**

**VASILE URECHE, ALEXANDRU M. IMBROANE**

**University of Cluj-Napoca, Astronomical Observatory**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract*. The components of the metric for a rotational relativistic
configuration with axial symmetry developed in spherical harmonics has
been put in a non-dimensional form. The differential system has been integrated
in the homogeneous case. The stability conditions for some values of parameters
*p_ *and *q*_ have been obtained.

*Key words*: relativistic stars - rotation.

** **

**ANGULAR
MOMENTUM AND ROTATIONAL KINETIC ENERGY FOR RELATIVISTIC POLYTROPES**

**ALEXANDRU M. IMBROANE**

**University of Cluj-Napoca, Astronomical Observatory,**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract*. The angular momentum and the rotational kinetic
energy in non-dimensional form have been determined for some values of
*n* and *p*_ for relativistic polytropic stars, in the spherical
symmetry case.

*Key words*: relativistic stars - rotation

** **

**TEMPORAL
VARIATIONS OF SOLAR ACTIVITY INDICATORS DURING CYCLE 22***

**GEORGETA MARIS, SIMONA DINULESCU, CRISTINA DUMITRACHE**

**Astronomical Institute of the Romanian Academy,**

**Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania**

*Abstract.*The present paper investigates the statistical behaviour
of sunspots, flares and rapid processes in solar prominences during the
ascending phase of the solar cycle 22 (SC 22). The North - South (N - S)
asymmetry for phenomena taken into consideration is analysed.

**We can remark that the flare number as well as the energetic flares
for SC 22, until 1991, have already overtaken the corresponding ones for
the whole SC 21.**

*Key words*: solar activity: sunspots, flares, prominences.

** **

**CORRELATION
BETWEEN THE LONG RADIOWAVE PROPAGATION AND THE GEOMAGNETIC FIELD**

**GEZA SZOCS**

**Teacher Training Institute, Eger, Hungary**

*Abstract*. The correlation between the intensity of the radioelectric
field of 155 kHz (emitted by Bod - Brasov and received by Cluj-Napoca)
and the amplitude of the horizontal component of the geomagnetic field
during February - March 1970 is estimated (research performed in the framework
of the INTERCOSMOS programme). A delay of three days in the ionospheric
response is pointed out. The magnetophere-ionosphere-Earth system is modelled
by an *RL *circuit.

*Key words*: geomagnetic field - ionospheric absorption - solar-terrestrial
relations.

** **

**INTERPLANETARY
MAGNETIC FIELD INFLUENCE ON THE LOW IONOSPHERE**

**GEZA SZOCS**

**Teacher Training Institute, Eger, Hungary**

**HURA SZOCS**

**Rando Kalman Engineering Institute, Székesfehérvar,
Hungary**

*Abstract*. The correlation between the interplanetary magnetic
field induction (measured by *Pioneer 3* during July 1980) and the
absorption of the radiowaves of 128.048 kHz and 245 kHz in the low ionosphere
is estimated. A delay in the ionospheric response of 3 - 4 days and a maximum
absorption effect after 7 - 9 days are found.

*Key words*: solar -terrestrial ralations - ionospheric absorption.

** **

**ON THE
PHYSICAL AND DYNAMICAL PROPERTIES OF ASTEROIDS**

**MIREL BIRLAN**

**Astronomical Institute of the Romanian Academy**

**Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania**

*Abstract*. The paper presents an attempt to study the connection
between the physical and dynamical properties of the asteroids. We have
studied a sample consisting of 301 asteroids, taking into account eight
physical parameters and three dynamical parameters. The method used is
the Principal Components Analysis, with which we have searched clusters
of asteroids in the histograms obtained in appropriate plans of the parameter
space. We have presented also a first comparison with the Tholen taxonomy
and with the Hirayama families.

*Key words*: asteroids, multivariate analysis, principal components
method.

** **

**EFFECTS OF THE
POLE MOVEMENT ON TIME DETERMINATIONS**

**MAGDA STAINSCHI, DANA DINESCU, GHEORGHE VASS, ALINA DONEA**

**Astronomical Institute of the Romanian Academy,**

**Cutitul de Argint 5, 75212 Bucharest 28, Romania**

*Abstract*. Between 1957 and 1990, observations were made in
Bucharest with a passage instrument, in order to measure the non-uniformities
in the Earth's rotation. We set out to analyse the way in which longitude
variations may affect the periodicities indicated by the raw UTO - AT observations
(Rom. Astron. J., Vol. 3, No. 1, 1993).

*Key words*: Earth's rotation, pole meovement, spectral estimators.

** **

**CONTRIBUTION
TO THE OPTICAL POSITION STUDY OF ____ PERSEI RADIO STAR, CARRIED OU IN
THE PERIOD 1969 - 1979**

**MIHAELA LICULESCU, PETRE POPESCU**

**Astronomical Institute of the Romanian Academy,**

**5 Cutitul de Argint St., 75212 Bucuresti, Romania**

*Abstract.*50 optical positions of ___ Persei, observed with
the Bucharest Meridian Circle in the Double Stars, NPZT and PZT stars programmes
have been compared with similar observations carried out at the Paris and
Bordeaux Observatories.

*Key words*: Meridian observations, ___ Persei.

** **

**ON THE
EXISTENCE OF CELESTIAL BODIES WITH UN PREDICTABLE MOTION IN THE SOLAR SYSTEM
AND ON THE KIRKWOOD GAPS**

**LENNARD F. BAKKER* and FLORIN N. DIACU****

**Department of Mathematics and Statistics,**

**University of Victoria, Victoria, B.C. Canada**

*Abstract*. The goal of this paper is to bring to the attention
of the astronomic community the recent mathematical results of Xia on the
existence of the Arnold diffsion in the 3 - body problem and to speculate
on its significance for the astronomy of the solar system. We bring evidence
that thus result supports the idea of the existence of small celestial
bodies with unpredictable behaviour and may expalin completely the formation
of the Kirkwood gaps in the belt of asteroids without contradicting previous
mathematical studies on this subject.

** **

**LIE
SERIES AND COMPUTER ALGEBRA TREATMENT OF THE n - BODY PROBLEM**

**BAZIL PARV**

**Babes - bolyai University Cluj-Napoca,**

**Faculty of Mathematics and Computer Science**

**Str. M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania**

*Abstract*. The solution of the *n *- body problem (up
to the required accuracy order) is given using the Lie series formalism
and computer algebra. The symbolic processing generates the FORTRAN source
code which calculates numerically the Lie series terms. This generator
of FORTRAN programs is general since the number of bodies and the maximum
order in expansions are input parameters. It admits further developments
according to the concrete problem to be solved.

*Key words*: Celestial Mechanics - *n*-Body Problem - Lie
Series - Computer Algebra.

** **

**ORBITAL
MOTION WITH LINEARLY CHANGING EQUIVALENT GRAVITATIONAL PARAMETER**

**VASILE MIOC**

**Astronomical Institute of the Romanian Academy,**

**Astronomical Observatory Cluj-Napoca**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract*. Considering that the equivalent gravitational parameter
of a two-body dynamic system is linearly time-dependent, *µ = A
+ Bt*, the behaviour of an elliptic-type orbit is studied. The perturbations
of all orbital elements are determined to first order in *B*, using
Delaunay-type canonical variables and a method due primarily to von Zeipel.
Solving the equations of motion, besides periodic perturbations, one points
out secular and mixed perturbations in semimajor axis and eccentricity
(hence unstable orbit), as well as in the mean anomaly, and mixed perturbations
in the argument of pericentre (hence apsidal motion). As expected, the
semilatus rectum and the position of orbit palne remain unchanged. The
model can be applied to various concrete astronomical situations.

*Key words*: celestial mechanics - perturbed orbital motion
- equivalent gravitational parameter - von Zeipel's method.

** **

**EFFECTS
OF ATMOSPHERIC DENSITY SEMIDIURNAL VARIATION ON ARTIFICIAL SATELLITE DYNAMICS**

**VASILE MIOC, EUGENIA RADU**

**Astronomical Institute of the Romanian Academy,**

**Astronomical Observatory Cluj - napoca**

**Str. Ciresilor 19, 3400 Cluj-Napoca, Romania**

*Abstract*. The separate influence of the semidiurnal variation
of the atmospheric density (whose distribution is described by the TD thermospheric
model) on artificial satellite motion is studied. First order effects are
pointed out through both perturbations of orbital elements over one nodal
period, and the difference between the nodal and Keplerian periods. The
respective analytic formulae are deduced for satellites moving in low eccentric
orbits. Some particular cases are discussed.

*Key words*: artificial satellites - atmospheric drag perturbations
- TD thermospheric model.

** **

**ON THE
DETERMINATION OF THE AERODYNAMIC DRAG PARAMETER OF INTERCOSMOS 19 ROCKET
( 1979 - 20B)**

**MAGDALENA CARSMARU, TIBERIU OPROIU**

**Astronomical Institute of the Romanian Academy**

**Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania**

*Abstract*. In the present paper we have presented the determination
of the aerodynamic drag parameter of Intercosmos 19 Rocket. We have used
the Goral's method, which we have applied also in the case of DTM and of
C atmospheric models. The results are in agreement with the values obtained
by means of the "classical" method.

*Key words*: Artificial satellites, Upper Atmosphere, Aerodynamic
Drag Parameter.** **
** **