First phase of active regions and their relation to the chromospheric network

An analysis of 63 young active regions shows that they originate exclusively on the borders of the chromospheric cells. In most cases they do not produce pores or spots, but always arch filament systems and chromospheric faculae. The arch filament systems evolve along the cell border, they are rooted on the network and not in the interior of the chromospheric cells. The sub-photospheric magnetic flux seems to reach the photosphere in units of 10¹⁹ Mx. About 3 hr after the first arch filaments appear pores evolve on the cell border. The pores and spots are probably formed by local aggregations of the emerging flux tubes.Mitteilungen aus dem Fraunhofer-Institut Nr. 132.     

OnH-functions of radiative transfer

Chandrasekhar'sH-functionH(z) corresponding to the dispersion functionT(z)=| _rs –frs(z)|, where [f _rs (z)] is of rank 1, is obtained in terms of a Cauchy integral whose density functionQ(x, ₁, ₂,...) can be approximated by approximating polynomials (uniformly converging toQ(x)) having their coefficients expressed as known functions of the parameters _r 's. A closed form approximation ofH(z) to a sufficiently high degree of accuracy is then readily available by term by term integration.     

Three-colour photometry of GH pegasi

The geometrical elements of the system GH Pegasi and a slightly improved period of 2 _. ^d 556136 have been given.     

Hydrogen and helium spectra in large magnetic fields

The energy levels and wave functions of hydrogen and helium atoms in the presence of large (10⁷G) magnetic fields are found by assuming that the eigenvalues and eigenvectors may be approximated by those of a truncated Hamiltonian matrix. In these atoms, fields of this size produce, in addition to the usual Paschen-Back effect, a quadratic Zeeman effect. This contributes an upward shift to the energy of all levels, which at sufficiently high fields dominates the Paschen-Back splitting.The behavior of a number of eigenvalues and wave functions as a function of magnetic field is presented. The effects of the field on the wavelengths and strengths of the components of H and the helium lines 4471, 4026 and 4120 as well as the forbidden 4025 are examined. In hydrogen the lines are split into components attributed to the now nondegenerate transitionsnlm _lnlm_l. In helium forbidden lines are excited, which may develop strengths larger than those of the allowed lines.     

Lunar velocity structure and compositional and thermal inferences

Seismic data from the Apollo Passive Seismic Network stations are analyzed to determine the velocity structure and to infer the composition and physical properties of the lunar interior. Data from artificial impacts (S-IVB booster and LM ascent stage) cover a distance range of 70–1100 km. Travel times and amplitudes, as well as theoretical seismograms, are used to derive a velocity model for the outer 150 km of the Moon. TheP wave velocity model confirms our earlier report of a lunar crust in the eastern part of Oceanus Procellarum.The crust is about 60 km thick and may consist of two layers in the mare regions. Possible values for theP-wave velocity in the uppermost mantle are between 7.7 km s^–1 and 9.0 km s^–1. The 9 km s^–1 velocity cannot extend below a depth of about 100 km and must decrease below this depth. The elastic properties of the deep interior as inferred from the seismograms of natural events (meteoroid impacts and moonquakes) occurring at great distance indicate that there is an increase in attenuation and a possible decrease of velocity at depths below about 1000 km. This verifies the high temperatures calculated for the deep lunar interior by thermal history models.Paper presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.     

Stochasticity of two comets in resonance with Jupiter

The orbital stochasticity of comets P/Ciffréo (1985 XVI) and P/Maury (1985 VI), at the present time near the 5/3 and 4/3 resonances with Jupiter, is investigated using Lyapunov Characteristic Indicators. First results indicate a strong stochastic behaviour for the two comets, mainly induced by encounters with Jupiter, which looks roughly like the behaviour of the group of comets in 1/1 resonance with Jupiter.     

The substructure of the local group

The subclustering within the Local Group is studied by means of the recently developed treediagram technique, enabling one to establish substructures of different boundness. Thirty-two galaxies from 39 listed are shown to form an interacting system which includes Milky Way and M31 giant spirals; we define the Local Group as that interacting system only. Second-level boundness indicates two clear subsystems, influenced by Milky Way and that of M31. The search of systems bound stronger, specifies several pair galaxies of similar morphology.     

Effect of temperature gradient on the wave propagation in a self-gravitating medium and its role in the central region of our Galaxy

The wave propagation in a finitely conducting, self-gravitating, non-relativistic hydromagnetic medium with temperature gradient and a heat-energy transport into it has been considered. Firstly, a General Dispersion Relation (G.D.R.) has been derived. The interest has been kept limited for the study of one dimensional wave propagation in a typical medium where magnetic field and it's gradient, density gradient, temperature gradient are all along the direction of wave propagation. The D.R. of such a medium follows from G.D.R. In particular, the effect of temperature gradient on the wave propagation has been studied. Analytical expressions for the wave parameters have been derived under different conditions. It has been found that the longitudinal waves could be sufficiently energetic for being unstable by the temperature gradient. Further, the modified Jeans' criterion (depending on temperature gradient), a criterion important for stability, has also been obtained.On assuming the gas medium in the central region ( 10 pc) of our Galaxy to behave like hydromagnetic fluid, and the direction of wave propagation (z-direction) as the direction perpendicular to the Galactic plane, few numerical estimations for the wave parameters (like wave lengths, phase velocity, etc.) have been made (as application of the above theoretical discussions). It has been found that the phase velocity of longitudinal waves at 1 pc level is at least 170 kms^–1 while at the 10 pc level the longitudinal waves of length less than a parsec may propagate smoothly through the medium. It has been suggested that (i) in the central region ( 10 pc) of our Galaxy the temperature gradient could be one of the major causes of the mass-outflow along the direction perpendicular to the Galactic plane (ii) outside the central region ( 10 pc) of our Galaxy, there may be long term consequences of such mass-outflow like Halo formation.