The influence of return current losses on pulse beam heating of the solar atmosphere is studied using a 1 D-hybrid code. While heating of the coronal plasma by the penetrating electron beam is obtained, as expected, strong return current losses of beam electrons at the resistivity jump in the transition region are also found. The electron beam energy is deposited at greater heights in the solar atmosphere than in the case of pure collisional losses. At the starting time of the flare, due to a strong return current heating, a very steep transition region is formed where upwards and downwards plasma flows are generated. However, this state has a transitory character. The atmosphere is heated and a channel of hot, low resistivity plasma is formed, by which the following electron beams can penetrate more easily to deep chromospheric levels, where they are then thermalized.
From an analysis of 624 UBV observations of LQ And made at six observatories between 1980 and 1988 we find a period of 0.30952 or 0.61904 days with a full amplitude of approximately 0.025m. There are weak indications of small irregular changes of amplitude and/or shape of the light curve, but no evidence of multiperiodicity. LQ And is thus a Be star with one of the most stable periodic light curves known. Although we are still unable to identify the true physical cause of the periodic light variations observed (pulsation, rotation or duplicity), we argue that the true rotational period of the star is in all probability close to the 0.619-day period. Additionally, we present some evidence of a gradual secular decrease in the brightness of LQ And between 1951 and 1988, possibly connected with weakening of the Balmer emission observed over a similar interval of time.A comprehensive analysis of the six comparison and check stars that have been used for LQ And confirms earlier reports that HD 224 166 is variable. We derive a new period of 3.5112 days for its light and colour variations, and suggest that this hot CP star is probably an oblique rotator. We also suspect kappa And of microvariability at the 0.01m level and advise caution when using this star as a photometric standard.
This paper deals with obtaining intermediaries for the Main Problem in the Theory of the Earth's Artificial Satellites by means of Lie canonical transformations. A suitable change of the independent variable renders the choice of the first-order terms in the new Hamiltonian natural, and the calculation of the respective periodic generating functions then becomes straightforward.
Radar meteor observations from Ondrejov, Czechoslovakia, and from Ottawa, Canada, have been used to determine the number density of meteoroids through the cross section of the Quadrantid meteor stream. The observations comprise 42 campaigns in the period 1958 to 1987 from two stations separated by 90-degrees of longitude and total more than 95 000 radar echoes of shower meteors. On average, the shower activity peaks at solar longitude 282.6-degrees (epoch 1950.0) relatively independent of the mass of the meteors because shifts due to mass sorting in individual years are smoothed out over long periods of time. Cross sectional profiles to a resolution of one hour of Earth motion are calculated for classes of echo duration (particle size) spanning radio magnitudes approximately from + 6 to -2.
Analysis of the radial velocities from 158 new photographic, Reticon and CCD spectrograms as well as from 266 older velocities found in the astronomical literature indicates that 5 Dra is the primary component of a binary system in a circular orbit with P(orb) = 61.55 days and K = 6 - 7 km/s. The basic physical properties of this system show clear similarities to other known Be binaries (al low-mass secondary, phase-locked V/R variations and a period in the range between about 10 and 500 days). The controversial short period of 0.890384 days - reported by early observers but later questioned - is reconfirmed here in older data, but does not appear clearly in more recent observations. Several periods between about 0.3 and 1.1 days are detected by us in velocity, line-widths and line-asymmetry measurements at different epochs. We show that these periods and other short periods reported in the literature (based on polarimetry and observations of travelling subfeatures in the line profiles) are all aliases and/or harmonics of the 0.890-day period. Therefore, we argue that a single physical periodicity (perhaps corresponding to the star's rotation) may be responsible for the rapid variations seen in 5 Dra.
It is shown that a particular Meshcherkij's type solution to the problem of two fixed centres can be found. This solution corresponds to the simultaneous escape of a test particle and the change of "oblateness" of the centres.
The Laplace-Lagrange secular theory applied by Yokoyama et al. to the 3/1 and 2/1 asteroidal resonances is used to obtain formulae for the instability region of the first-order resonance p = (p + 1)/p. As this approach yields the instability region even for 3/2 resonance, where Hildas are observed, it is concluded that this calculation in itself cannot explain the origin of Kirkwood gaps and that more refined methods allowing to calculate the maximum eccentricity have to be applied.
The paper deals with the problem of mathematical description of meteoroid heating during pre-ablation phase of its atmospheric motion. Only the terms linear in temperature are considered, i.e. the radiation is not taken into account. As compared with Levin dealing with meteoroid represented by infinitely long cylinder, and with Ceplecha and Padevet considering the sphere heated by the surface energy influx proportional to exp t, we obtained more general formula valid for any kind of energy influx applied at the sphere surface. This generalization enables further problems of meteoroid heating, which were not considered so far, to be treated. We can take into consideration the anisotropy of the energy influx arising from the meteoroid motion, the influence of the body deceleration due to drag exerted by the atmosphere, more realistic atmosphere density profile than the barometric one videly used so far, and the proper rotation of meteoroid. Each problem mentioned above was solved using the method of integral transforms which was recognized as a mathematical tool enabling to provide us with solution represented by analytical formula. The method of integral transforms is briefly outlined in Appendix A where also some formulae employed in the main text are derived. Appendix B deals with some analytical expressions necessary for quick computation of coefficients depending on psi, the angle between the velocity vector and the vector of the body rotation axis, introduced also in the main text.
In the previous study of CV Cyg (Vetesnik and Perek 1966) it was concluded that the system probably showed no period variation. Now, 27 new times of minima have been added to the other 39 found in the literature. Analysing these data, we could obtain some evidence of possible period changes of this eclipsing system. The period of CV Cyg decreases: dP/dt = (-1.175 +/- 0.078) x 10(-9) [day/cycle]. Referring to this behaviour the system should be in the status of rapid mass exchange.
Generalized lumped coefficients, valid for resonant, m-daily and zonal perturbations with the relevant indices for C(lm)BAR, S(lm)BAR, F(lmp)BAR(I) and G(lpq)(e), are presented.
The radiant motion and orbit of the Lyrid meteor stream is determined from 14 precisely reduced photographic meteors observed in the period 1941-1985. The scatter in the orbital elements is extremely small. The mean Lyrid orbit is practically identical with that of P/Comet 1861 I. The mean photographic orbit is compared with that determined from radar measurements.
Using the TD model to describe the density distribution of the upper atmosphere, analytical expressions for the aerodynamic drag perturbation undergone by five independent orbital elements of an artificial satellite, over a nodal period, are established. All the three components of the perturbing acceleration are taken into account. The variations of the orbital elements are obtained in a very concentrated form.
Shock wave velocities at 126 points in the solar equatorial plane, within 1 AU, are obtained from a 2-D MHD model. These simulations are compared with those from a semiempirical model of shoch wave propagation. Shocks with the three different initial velocities, v = 1000, 1500 and 2000 km/s, were considered.
The motion of an orbiter in low eccentric orbit in Mars' atmosphere is studied. The approximation of a spherically symmetrical, rotationless atmosphere is considered. The difference between the perturbed nodal and the corresponding Keplerian period is analytically estimated. The perturbations undergone by five independent orbital elements, over a nodal period, are established, too.
New times of minimum light were measured for several early-type eclipsing binaries: V337 Aql, V1182 Aql, V1331 Aql, IU Aur, QZ Car and V382 Cyg. The O-C diagram for these systems is discussed and new ephemeris is given for AH Cep; observation of AQ Cir is added. It is shown that the scatter of times of minima is several times larger than the measuring errors for most of the binaries studied.
Motions in the strong bar galaxy NGC 1365 are analyzed with the radial velocities published by Jorsater et al. (1984). We found that, inside the bar, the highly elliptical streamlines are aligned with the bar major axis. Further out the less elliptical streamlines are inclined to the bar major axis at 10-degrees to 30-degrees. The residual velocity dispersion between 15 to 25 km s-1 is much less than that found earlier. Some large residuals near the bar end may be due to the chaotic orbits predicted by Pfenniger (1984). However, the conclusion suffers from many gaps in the data coverage of the galactic plane. Additional observations in some key regions of NGC 1365 are urgently needed.
We compare the new index of recurrence of enhanced geomagnetic activity with the latitudinal and longitudinal distribution of solar magnetic fields and prominences for the recent two eleven-year cycles of solar activity. It is demonstrated that the streamers of the solar wind causing the considerable enhancement and regularity in recurrences of large geomagnetic disturbances during the descending phase and before the end of an eleven-year cycle, are anchored into the system of magnetic fields formed by the fields of the old eleven-year cycle of solar activity.
Numerical simulation of interplanetary disturbances requires to know, as initial background, the steady-state solar wind. Its parameters are unambiguously determined by values of the MHD variables at the inner boundary. Usually, it is requested to specify here such values which determine the solar wind with values close to observations at 1 AU. This task is performed by trial computations and the main purpose of the paper is to provide some help. Position of the inner boundary is chosen at 18 Rs which is frequently used and lies in the supersonic flow region. Because the magnetic field has a little effect on the steady-state, the MHD task is split into solution of hydrodynamic equations and using simple relations to determine supplementary variables. Large set of such computations is performed and their results processed to graphical form for their easy use. The presented procedure is compared with complete 1D HD and 2D MHD computations.
