STRUCTURAL
PARAMETERS OF
DY PEGASI
LIGHT CURVES
BETWEEN 1949
– 1987
ALEXANDRU POP,
ADRIAN CRISTEA,
VLAD TURCU
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania
E-mail: apop@academie.cj.edu.ro, acristea@usa.net
Abstract. Structural changes of
DY Pegasi light curve shape are being studied using both traditional and
Fourier-type structural parameters. In order to perform this investigation
we applied the Fourier decomposition technique to each considered data
set.The values of the above mentioned structural parameters were then calculated.
THE
22-YEAR SOLAR
MAGNETIC CYCLE.
I. SUNSPOT
AND RADIO
ACTIVITY
GEORGETA Maris, ADRIAN Oncica,
MIRUNA DANIELA Popescu
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: gmaris@aira.astro.ro, adrian@aira.astro.ro,
miruna@aira.astro.ro
Abstract. The magnetic polarities
of the solar active regions in each hemisphere reverse from one 11-year
activity cycle to the next. The same is true for the polarity of the poles.
Thus, the magnetic solar activity exhibits a 22-year recurrence
known as the Hale Cycle. Previous studies have suggested that the
correct choice for cycle pairing is "even-odd" (in that order) the second
one being more powerful. Based on a bimodal behaviour of even-odd solar
cycle pairs, it was predicted a higher amplitude for the solar cycle 23.
Nevertheless this cycle reached its maximum smoothed number RM
of only 120.8, much lower than the predicted value. We analyse sunspot
relative numbers and 10.7 cm radio flux data during the ascending phases
of the 11-year solar cycles 22 and 23. In order to point out possible intrinsic
different behaviour between the odd – even components of the magnetic cycle,
we limit ourselves to the ascending phases only. These periods are less
influenced by the overlapping effect seen usually on the descending phase.
We investigate spectral features in our time series data together with
their time evolution using some of the tools provided by Joint Time-Frequency
Analysis. We found substantial lack of correlation between the two ascending
phases. Our JTF Analysis showed also different trends in time behaviour
and variability content.
FAMILIES
OF STRAIGHT
LINES
IN PLANAR
POTENTIALS
GEORGE BOZIS 1,
MIRA-CRISTIANA ANISIU 2
1 Department of Physics,
University of Thessaloniki
GR-54006 Thessaloniki, Greece
E-mail: gbozis@ccf.auth.gr
2 "Tiberiu Popoviciu"
Institute of Numerical Analysis
P. O. Box 68, RO-3400 Cluj-Napoca, Romania
E-mail: mira@math.ubbcluj.ro
Abstract. It is shown that all
planar potentials V(x, y) that can give rise, among
other conditions, to monoparametric families of straight lines (FSL) satisfy
a condition, expressed in the form of a second order nonlinear partial
differential equation in V. To each such potential there corresponds
just one FSL, whereas each preassigned monoparametric FSL can be created
by infinitely many potentials. Various types of potentials (e.g., separable,
homogeneous, etc.) producing FSL are studied. A necessary and sufficient
condition is found, satisfied by all "adelphic" families of orbits, i.e.
families that can coexist with a given FSL.
THE
EQUILIBRIUM POINTS
IN THE
PHOTOGRAVITATIONAL MODEL
OF CONSTANTIN
POPOVICI
VASILE MIOC
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: vmioc@aira.astro.ro
CRISTINA BLAGA
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania
E-mail: cpblaga@math.ubbcluj.ro
Abstract. We discuss the two-body problem within
the framework of the photogravitational model proposed by the Romanian
astronomer Constantin Popovici. The motion equations in polar coordinates
and the angular momentum integral are established, then transposed in McGehee-type
variables. The qualitative analysis of the differential system allows an
easy identification of the equilibrium points, as well as the study of
their nature. The results are compared with those obtained by other authors.
A
NEW ANALYTIC
SOLUTION FOR
THE MANEV-TYPE
TWO-BODY PROBLEM
CRISTINA STOICA 1,
VASILE MIOC 2
1 University of Victoria,
Department of Mathematics and Statistics
Victoria, B. C., V8W 3P4, Canada
E-mail: cstoica@math.uvic.ca
2 Astronomical Institute
of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: vmioc@aira.astro.ro
Abstract. The analytic solutions
of the Manev-type two-body problem, obtained both perturbatively and by
direct integration are being revisited. A new solution is provided starting
from the first integral of energy. The equivalence of the new solution
with the old ones is proved.
A
NEW SET
OF LISSAJOUS-TYPE
COORDINATES
FOR HAMILTONIAN
SYSTEMS
C?T?LIN CUCU-DUMITRESCU
Computer M&S 95
Bd. Aviatorilor 23, Bucharest, Romania
E-mail: ufh@pcnet.ro
Abstract. The motion described
by two-degrees-of-freedom canonical systems is being considered. One passes
from Cartesian to polar coordinates, then makes the system autonomous.
The second step introduces Levi-Civita parabolic polar coordinates and
rescales the time. At the last step, a new set of Lissajous-type coordinates
is introduced. These ones give a remarkable form to the Hamiltonian, making
its main part directly integrable. Some concrete astronomical situations
to which the model is applicable are presented.
INFLUENCE
OF THE
EVEN ZONAL
HARMONICS
OF THE
GEOPOTENTIAL ON
GPS SATELLITE
ORBITS
STELIAN COJOCARU
Romanian Naval Academy, Navigation Department
Str. Fulgerului 1-3, RO-8700 Constanta, Romania
E-mail: cojocarus@yahoo.com
Abstract. The Global Positioning System represents
the most widespread, latest fashioned tool for astronomers, geodesists,
hydrographers and navigators in their attempt to determine the positions
of points of interest on the Earth, sea and space. The paper investigates
the most important part of the perturbing acceleration that influences
the GPS satellite osculating elements: the non-central part of the gravitational
field of the Earth. First, an analytical investigation of the effect of
zonal harmonics of the geopotential is performed. Second, a numerical,
discriminatory evaluation is achieved and finally a few important conclusions
are being drawn.
OBSERVATIONS
OF PLUTO
IN BUCHAREST
DURING 1932
AND 1967-1975:
PRECISE POSITIONS
AND MAGNITUDES
GHEORGHE BOCSA
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: gbocsa@aira.astro.ro
Abstract. The
observations of Pluto obtained in 1932 and during 1967-1975, performed
at the Astronomical Observatory of Bucharest with the 380/6000 mm astrograph
are presented. Both Turner's (constants) and Schlesinger's (dependencies)
methods were used for the computation of the normal coordinates of the
object.
HARETU
AND THE
STABILITY OF
THE SOLAR
SYSTEM
FLORIN DIACU 1,
TUDOR RATIU 2
1 Pacific Institute
for the Mathematical Sciences
and
Department of Mathematics and Statistics
University of Victoria, P. O. Box 3045
Victoria, B. C., V8W 3P4, Canada
E-mail: diacu@math.uvic.ca
2 Département
de mathématiques
École Polytechnique Fédérale de
Lausanne
CH-1015 Lausanne, Switzerland
E-mail: Tudor.Ratiu@epfl.ch
Abstract. We discuss the contributions of Spiru
Haretu to the problem of the solar system's stability and show their importance
relative to the mathematics research of the late 19th century. We also
give a brief survey of the subsequent developments and the consequences
of Haretu's results.
SPIRU
HARET'S CONTRIBUTION
TO CELESTIAL
MECHANICS
VASILE MIOC, MAGDA
STAVINSCHI
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: vmioc@aira.astro.ro, magda@aira.astro.ro
Abstract. The contribution of Spiru Haret to
astronomy, especially to the problem of solar system stability, is being
emphasized. The pre- and post-Haret results in this domain are also pointed
out.