Accuracy assessments of recent earth gravity models using crossover altimetry     

Jaroslav Klokočník  Carl A. Wagner  Jan Kostelecký 《Studia Geophysica et Geodaetica》1996,40(1):77-110

Summary The calibrated variance-covariance matrices of the harmonic geopotential coefficients of the recent combined model JGM 2 has been tested and verified by independent crossover altimetry from TOPEX/Poseidon and ERS 1 using the Latitude Lumped Coefficients in the southern oceans area. Although orbits are not yet available for these missions with other recent models for which error matrices have been released, by comparison with JGM 2 results and field differences we also confirm that the error matrices for the satellite model GRIM 4S4p and the combined data model JGM 3 are also generally valid. Projections of these matrices for a variety of inclinations show that many unused orbits of even moderate altitude (≈ 800 km) will still yield trajectory crossover errors at a level of many tens of centimeters even with the latest orbitgeopotential models.  相似文献   

A preliminary seismic model for the region of the west-Bohemian earthquake swarms     

Oldřich Novotný 《Studia Geophysica et Geodaetica》1996,40(4):353-366

Summary A layered model of the crustal and upper mantle structure for the region of the West-Bohemian earthquake swarms is proposed. This model represents a compilation of the results of deep seismic soundings, surface-wave investigations, and some local seismic measurements in the western regions of the Bohemian Massif.  相似文献   

The simulation of the initial mass function and star formation efficiency     

Marek Wolf  Vladimir Vanýsek 《Astrophysics and Space Science》1986,128(1):229-235

The fragmentation of a molecular cloud is modelled as a random process by the Monte Carlo method. The probability of the fragmentation is a function of the cloud initial mass and decreases rapidly for mass lower than critical mass, which is a defined parameter. The modelled IMF is compared with the mean mass function in open clusters assumed here as the observed IMF. The best fit was found for initial mass 3×10³ M _s and for the critical mass range 0.4 to 0.6M _s . It also implies the star formation efficiency to be about 0.3.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.  相似文献   

Theoretical spectra of cataclysmic variables     

S. Křiž  I. Hybený 《Astrophysics and Space Science》1987,130(1-2):341-349

We present two methods of modelling accretion disks in dwarf novae. The first one determines self-consistently the structure of a disk together with the radiation field. The computed theoretical spectra agree well with the observations of the dwarf nova WX Hyi in quiescence as well as in superoutburst. The second method is a modification of Tylenda's (1981) approach. We have used it to calculate models of disks around main-sequence accretors. The most interesting result is that no unique solution exists for a moderate mass flux around 10^–6 Myr^–1. Such disks are thus probably unstable.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.  相似文献   

Hα diagnostics of (post)-flare loops based on narrow-band filtergram observations     

P. Heinzel  M. Karlický 《Solar physics》1987,110(2):343-357

Using narrow-band H filtergrams, we develop a quantitative non-LTE approach to determine the physical conditions prevailing at the tops of (post)-flare loops observed against the solar disc. At temperatures 10000–15000 K, the tops of flare loops turn to emission at H line center when the gas pressure P _g reaches 1 dyn cm^–2 and should be clearly visible for P _g 3 dyn cm^–2, independently of the loop diameter. This situation corresponds to the electron density of the order 10¹² cm^–3. The contrast of flare-loops (in projection on the disc) at H line center is mainly the function of P _g , while in the line wings (H ± 1 Å) the loop can be visible in absorption or emission only when rather strong microturbulence is present or for unrealistically high gas pressures. Finally, we briefly discuss our diagnostical results in frame of the latest (post)-flare loop model.  相似文献   

The route to chaos during a pulsation event     

Jürgen Kurths  Marian Karlický 《Solar physics》1989,119(2):399-411

A time series analysis of a pulsation event in solar radio emission provides an evolution from a regular doubly periodic phase to an irregular behaviour. Applying some techniques developed in the theory of nonlinear dynamic systems to this irregular stage suggests that there exists a low-dimensional attractor. Estimates of the maximum Lyapunov exponent give some evidence to deterministic chaos. The sudden transition from a regular to a chaotic structure is identified as a part of the Ruelle-Takens-Newhouse route to chaos which is typical in nonlinear systems. It is checked whether this pulsation event may be interpreted in terms of known pulsation models. Consequences for models, which are suitable to describe such an evolution, are discussed.  相似文献   

Cosmological considerations and the special theory of relativity     

Vladimír Skalský 《Astrophysics and Space Science》1989,158(1):145-151

From the special theory of relativity it follows that the Universe is expanding during the expansive evolutionary phase with the limit velocity of the signal propagationc. The discovery of this fact throws a new light on a number of cosmological questions.  相似文献   

A note on the superluminal velocity in cosmological models     

Miloslav Dubec  Vladimír Skalský 《Astrophysics and Space Science》1989,162(2):341-342

This note removes a misunderstanding in the interpretation of solutions of the equations of motion in Friedmann's model.  相似文献   

A note on the problem of choosing a model of the Universe,I     

Vladimír Skalský 《Astrophysics and Space Science》1988,149(2):375-378

The author considers the possibility of transition of the current universe expansion to contraction. The considerations are based on the fact that a homogeneous Universe is structured into non-homogeneous units, the latter expanding as a whole. An analysis of the effects of these wholes on further development shows that in the future contractions may occur only locally; however, the current spatial expansion of the Universe cannot be replaced by a global contraction.  相似文献   

Is the Universe an actual subsystem of the infinite whole of reality?     

Vladimír Skalský 《Astrophysics and Space Science》1988,147(2):267-270

On the basis of the law of conservation of energy, the variations of radiation energy as a result of the variations of the dimensions of the Universe and of the increase in total energy of the hypothetical false vacuum, the author introduces an assumption that the Universe is an actual subsystem of the infinite whole of reality. Analyzing the consequences of introducing this assumption into the standard model of the Universe, he comes to the conclusion that the Universe, with respect to its evolution, represents an ultrastable system consisting of a dynamic system of the de Sitter evolution phase with the Planck values and of a dynamic system of Friedmann's phase of evolution into which the dynamics of its partial subsystems is incorporated.  相似文献