[en] During the last two decades, spacecraft projects and individual experiments for which Frank McDonald was a leader have contributed very significantly to the current understanding of the structure of interplanetary space and the correlation between solar and interplanetary disturbances. Studies on the IMP, HELIOS, and Pioneer spin-stabilized spacecraft and the larger attitude-stabilized Voyager spacecraft have provided data sets from which the modern view of the heliosphere has evolved. That concept in which the inner solar system is shown to be dominated by individual streams associated with specific source regions on the Sun is illustrated. As these high-speed streams overtake the preexisting solar plasma, they coalesce and modify the characteristics so that at larger heliocentric distances, these disturbances appear as radially propagating concentric shells of compressed magnetic fields and enhanced fluctuations

[en] The inverse problem of determination of the petrochemical composition and geologo-petrographical characteristic of the Venus rocks by content in the natural radioactive elements is stated. Data bank including U, Th, K contents, silicate analysis, the name, geotectonic position, bedding conditions, age has been collected. U, Th, K contents found experimentally in the Venus rocks in places of the ''Venera-8, 9, 10'' and ''Vega-1, 2'' interplanetary station landing are known. Probabilities of the Venus rock correspondence to the families of the Earth magmatic rocks are calculated. It is established that the rocks, investigated by the ''Venera'' and, ''Vega'' stations, are similar betwee each the coutent of natural radioactive elements and correspond most of all to sienites and trahydacites

[en] A Martian summer cloud was observed on the flank of Olympus Mons located 20 deg N and 137 deg W during the 1982 apparition. This cloud, hereafter referred to as the Olympus cloud, showed a diurnal variation of the apparent brightness over more than one month. The Olympus cloud appeared near the local noon (12 MLT; Martian local time), and its apparent brightness increased until 16 MLT. Based on the assumptions that the Olympus cloud is composed of H₂O ice and that the Martian atmosphere contains a constant amount of dust equivalent to the optical thickness of 0.4, we estimated the optical thickness of the Olympus cloud with the aid of the discrete-ordinate method. We found that the progression of the optical thickness of the H₂O ice cloud against the MLT shows the peak value of about 0.5 near 14 MLT. This peak value corresponds to 0.7 precipitable micrometer. (author)

[en] One can expect the presence of invisible mass (in the form of cometary nuclei) at the heliocentric distances 2x10³ < or approx. r < or approx 2x10⁴ a.u. if one assumes that the Oort cloud being only a rarefied halo surrounding the core (dense inner cometary cloud) and the mass of the comet Halley being typical for comets both in the core and the Oort cloud populations. The mass appears to be M ∼ 0.03 M_sun with the angular momentum of the order of 10⁵³ gcm²/s. This mass value is of the order of the total mass of the planetary system before the loss of volatiles. Therefore during of the protosolar nebula evolution of the formation of comets and planets was spent approximately equal masses

[en] The oscillations of Jupiter, if detectable, would constrain theories of its interior. This work predicts the pattern of expected pressure modes, using the ray tracing method. According to current models of internal structure, the planet exhibits two discontinuities in the sound speed. The first one is located in the hydrogen-helium envelope around the 3Mbar pressure level and corresponds to the transition of molecular to metallic hydrogen, while the second one corresponds to the transition between the envelope and the high density core. Observations of low degree p-modes, obtainable from the ground, would accurately provide the value of the radius of the planetary core; observations of high degree modes, conducted from space, would provide a signature of the external transition

[en] The MHD stability of the cometary ionopause is investigated by nonlinear analysis, describing that stability in terms of the finite perturbation amplitude of both Kelvin-Helmholtz and Rayleigh-Taylor modes. The evolution of the unstable modes is examined, determining the conditions under which finite amplitude effects are expected to stabilize a growing wave disturbance. The analysis is applied to the ionopause at Comet Halley and Comet Giacobini-Zinner, showing that the theoretical prediction concerning the stability of this interface based on an earlier linear analysis remains valid in both cases despite the nonlinear stabilization effects. 18 references

[en] We reanalyse positions and motion of the striae in the dust tails of the bright comets Mrkos 1957 V and West 1976 VI. Two theories are compared to the data: the high speed particle ejection theory of Notni (1964) and the two-step kinematical sequence proposed by Sekanina and Farrel (1980) in their particle fragmentation theory. The final decision is in favour of the two step sequence, though the real situation may be a mixtum compositum of both. The parent clouds (first step) are found to have low lateral velocity dispersion and higher than expected acceleration. The question how these clouds originate remains unsolved. It is suggested that they comprise particles which left the coma into a tailward region of high magnetic field and plasma density. Another possibility, additionally accounting for the sometimes apparent duplicity, is an out origin of an optically thick coma at angles orthogonal to the radius vector. (author)

[en] The results of ground-based spectrophotometry of the comet P/Giacobini-Zinner (1984) near perihelion and the time of the International Cometary Explorer (ICE) encounter are presented. It is found that the H₂O(+)/CO(+) abundance ratio is 1.2 + or - 0.6 compared with the ICE result of approximately five. Analysis of the dust production as measured by the optical continuum predicts a dust impact rate on the S antenna of the ICE of 0.01/s or less at closest approach. This upper limit is consistent with the ICE results. 21 references

[en] A thermal model of a cometary nucleus is analyzed on the basis of a numerical solution of the nonsteady heat-conduction equation with allowance for energy balance at the surface, variability of the thermophysical characteristics of the material, the influence of the dust component, and the proper rotation and orbital motion of the comet. The temperature fields are calculated and the reactive force generated in the anisotropic outflow of volatile components of the nucleus is estimated. Using the characteristics of the thermal model, a photometric model of the region near the nucleus is constructed, containing quantitative estimates of the optical properties of the nucleus and the gas - dust atmosphere. The problem of the brightness distribution in the vicinity of a cometary nucleus is investigated qualitatively

[en] On the basis of the model of the formation of the preplanetary nebula as an accretion disk during the formation of the sun, the hypothesis is proposed that a significant fraction of the solid materials of the preplanetary nebula was formed by the successive condensation of the components of the gas of solar composition during its motion from the hot, dense region near the protosun to the periphery of the nebula into regions of ever decreasing values of temperature and pressure. The hypothesis removes the contradiction materials and the presence of traces of high-temperature phenomena in chondrite materials and the conclusion that there were never high temperature in the preplanetary nebula at distances of 2-4 AU from the sun, where meteorites encountering the earth originate, and also explains a number of properties of chondrites. It follows from this hypothesis that the mass and angular momentum of the nebula were close to their minimum possible values and that the loss of the nebular gas had already begun at the final stage of its formation