Chinese Astronomy最新文献

This paper deals with the steady basic state of a disc galaxy with finite thickness. A hydrodynamical model is used and the zeroth and first order solutions in the small parameter thicknes/(overall radius) are obtained.

The steep temperature distribution with height in the solar chromosphere-corona transition zone is one of the unsolved problems in solar physics. This paper presents a qualitative and quantitative explanation to this steep distribution of temperature in terms of the pileup effect of the oscillations in a plasma and the mechanism of wave-particles nonresonant heating. Analysis shows that if a proton beam of high energy is continuously injected into the transition zone from the chromosphere, the steep distribution of temperature is able to appear in a narrow layer through the plasma wave-particles nonlinear interactions.

The spectrum of Nova Cygni 1975 obtained at the Beijing Observatory is further analysed here. The distance, interstellar absorption, intensity ratios of some emission lines of the nova, the temperature of the central star and the electron density and temperature in the expanding shell are derived. As the nova declined in brightness, both the temperature of the central star and the electron temperature increased and they showed similar fluctuations.

The different characteristics of the structure and dynamics of the terrestial, the cytherean, the martian and the jovian atmospheres have been analysed. Our analyses with one-dimensional and three-dimensional models show the thermal structure of the martian and jovian atmosphere to be similar to that of the terrestrial atmosphere. For these three atmospheres the dimensionless parameter of thermal structure α is of the order 1, which is in contrast to the small α (5 × 10⁻²) for the cytherean atmosphere.

This paper is devoted mainly to a method of determining the gradient of magnetic fields. Utilizing the numerical solution of the equations of transfer of the Stokes parameters, we have calculated quantities characterizing the asymmetry and the amount of rotation of the wings of the “o” and “e” profiles of the magnetically sensitive line Fe Iλ 6302.499 as functions of the magnetic field gradient. The results of calculations have been verified with our own spectrophotometric observations of a large sunspot. The range of validity of the method is discussed, and the possible influence of the presence of magnetic field gradients on the observational data of magnetographs is investigated.

Conclusion in [1] have been further verified. New results are: (1) If the electric potential ▿φ obeys the gauge relation $\text{∂}\text{A}\text{∂t}\text{·}\text{B}\text{=0}$ then the necessary and sufficient condition for α to be constant is $\text{▿×(}\text{V}\text{×}\text{B}\text{)=β}\text{B}\text{,}\text{∂}\text{A}\text{̀}\text{∂t}\text{=0}$. (2) An equation governing the behaviour of α has been derived, which shows that the electrical resistance is the agency that causes a non-constant α to evolve into a constant one.

We give the revisions to the FK4 Catalogue based on the observations made with a Type-1 photoelectric astrilabe in the period 1973 October to 1976 October, together with a description of the procedures and the accuracies obtained, and a study of the systematic errors of Δα_δ and Δδ_δ types in the catalogue. The results obtained show that the Type-1 photoelectric astrolabe is better than the Danjon astrolabe for the purpose of improving star positions.

A tracking system has been installed on the dome of the 60-cm telescope of the Peking observatory. The system uses rotating transformers to transform the coordinates, a relay-operated servo system, with a squirrel-cage induction motor as the executing component. The control system is a non-linear system. In addition to D.C. motor braking, position and velocity feedbacks are used to eliminate self-excited oscillations. The systematic error of the system does not exceed ±1°. The system costs less and is more reliable than a D.C. motor system.

Under the first-order Born approximation of scattered field, we have derived the expressions (17), (26) and (30) for the phase fluctuations caused by small scale irregularities in the atmosphere together with a discussion of the effects of irregularities of different sizes on radio interferometer measurements.