Reviews     

Vojtěch Vítek 《Studia Geophysica et Geodaetica》1995,39(4):468-467

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The possibility of using the horizontal vector potential in numerical forecasting     

Vítek  Vojtěch  Vítková  Dagmar 《Studia Geophysica et Geodaetica》1963,7(4):407-409

Studia Geophysica et Geodaetica -  相似文献   

A giant coronal arch observed by Skylab     

Zdeněk Švestka 《Solar physics》1991,135(2):419-422

The limb event of 13 August 1973, observed by Skylab in soft X-rays, has all the typical characteristics of the giant post-flare arches observed by HXIS and FCS on board SMM in the 1980s. Skylab images provide us with 4–5 times better angular resolution than the SMM experiments and thus, for the first time, make it possible to distinguish the real fine structure of a giant post-flare arch. The image processing of the 13/14 August 1973 event is now in progress.  相似文献   

Solar research at the Ondřejov Observatory     

Švestka  Zděnk 《Solar physics》1970,12(2):332-340

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Enhanced X-ray emission above 3.5 keV in active regions in the absence of flares     

Aert Schadee  Cornelis De Jager  Zdeněk Švestka 《Solar physics》1983,89(2):287-305

We demonstrate that even in the absence of flares there are very often volumes of hot plasma in the corona above active regions with temperatures in excess of 10 million degrees. Characteristics of this hot plasma and its time variations seem to be different in active regions of different phase of development. These hot plasma regions are sources of very weak, but clearly recognizable, X-ray emission above 3.5 keV. Long-lived X-ray brightenings, 10⁴ times weaker than a flare, but lasting up to 10 hr occur predominantly along the H _∥ = 0 line, apparently low in the corona. After major flares, long-lived X-ray emission is also radiated from tops of arches extending high into the corona. Some other long-lived sources, far from the H_∥ = 0 line, may be associated with newly emerging flux. Short-lived X-ray sources, with fluxes ranging from subflare levels to 10^?3 times the flare flux, last for 2 to more than 30 min and are probably microflares. They seem to be most frequent in growing young active regions and appear often in areas with newly emerging flux.  相似文献   

Martha Betz Shapley     

Zdeněk Kopal 《Astrophysics and Space Science》1981,79(2):261-264

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The precession and nutation of deformable bodies,II     

Zdeněk Kopal 《Astrophysics and Space Science》1969,4(3):330-364

In a previous paper of this series (Kopal, 1968a) the Eulerian equations have been set up which govern the precession and nutation of selfgravitating bodies of viscous fluid in inertial coordinates which are at rest in space. In order to facilitate their solution, in the present investigation we shall transform these equations to the rotating body-axes; and shall explicitly evaluate all their coefficients arising as a result of second-harmonic dynamical tides.Following the introductory Section 1 which contains a mathematical statement of the problem, the requisite transformation of coordinates will be outlined in Section 2, and applied to the equations of motion in Section 5. The corresponding moments and products of inertia appropriate for selfgravitating configurations of arbitrary internal structure will be formulated in Section 4; while the deformation terms arising from second-harmonic dynamical tides raised on centrally-condensed configurations will be evaluated in Sections 3 and 6. The concluding Section 7 will then contain a specification of the components of the disturbing force.The next stage of our investigation — namely, a construction of the actual solutions of the equations governing precession and nutation of fluid bodies in different cases of astrophysical interest — has been postponed for a separate paper.  相似文献   

Dynamical tides in close binary systems     

Zdeněk Kopal 《Astrophysics and Space Science》1968,2(1):48-60

Differential equations governing the dynamical tides in close binary systems consisting of centrally condensed components of viscous gas are split up (Section 2) in their real and imaginary parts, the ratio of which defines the tidal lag. In Sections 3 and 4 these equations will be particularized to a case in which the central mass-point of each star is surrounded by an evanescent envelope the density of which decreases as the inverse square of the central distance. It is shown that self-gravitating configurations built up in accordance with this model are incapable of performing free nonradial oscillations with a frequency comprised between 0 ² ; but explicit expressions for forced oscillations representing dynamical tides are given for an arbitrary form of the external field of force. Equations for the imaginary components of the displacement, constructed for the same model in Section 4, disclose that if the viscosity of stellar material is identified with that of hydrogen plasma, the tidal lag due to a viscous dissipation of kinetic energy may produce dynamical effects, the cumulative outcome of which becomes appreciable on the Kelvin time-scale, but over short intervals of time their stationary photometric effects should be negligible. The latter can become observationally significant only for stars in which turbulent viscosity under near-adiabatic conditions becomes and important factor.  相似文献   

Photometric perturbations of distorted eclipsing systems within minima     

Zdeněk Kopal 《Astrophysics and Space Science》1987,134(2):235-259

The aim of the first part (Sections 1 and 2) of this paper will be to extend an analysis of the light curves of totally-eclipsing binary systems to the case in which the distortion of the shadow-cone of the eclipsing component must be taken account of in an analysis of the system's light changes within minima. Like in the case of total eclipses of spherical stars, an extension of the analysis of their light changes in the frequency-domain can likewise be carried out in a closed form, without a need to resort to automatic computers which may not be at the disposal of every investigator. In the second part (Sections 3 and 4) of this paper, the same procedure will be extended (albeit to a lesser degree of precision) toany type of eclipses—be these total, annular or partial; while a proof of the underlying formulae the reader will find collected in the Appendix. Again, in this more general case, while an access to automatic computers may be of advantage to incorporate the photometric perturbation arising from the distortion of the components mutually eclipsing each other, their use represents a convenience rather than necessity for our work.  相似文献   

Ray amplitudes of seismic body waves in inhomogeneous radially symmetric media     

Vlastislav Červený  Jaromír Janský  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1983,27(1):9-18

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