Chinese Astronomy最新文献

Our analysis of the relationship between coronal holes and geomagnetic storms lends support to the idea that the so-called M-regions are coronal holes with large areas. For two typical coronal holes examined, their equatorial extensions are found to be 25–50°. The time lag between the onset of the geomagnetic storm and the central meridian passage of the coronal hole is inversely correlated with the area of the latter.

Records of the 164 MHz fan beam interferometer of our Miyun Station at the times of coronal holes are examined. in general, these records show a regular variation, implying a diminished emission from the coronal holes and that the holes follow the solar rotation. Results from a “superposed diagram analysis” of the “central strip flux” demonstrate these effects even more clearly.

The possibility of using radio and sunspot data to determine the CMP of coronal holes is investigated and an attempt is made to evaluate the speed of the high-velocity solar stream and the size of the coronal hole from data on recurrent geomagnetic storms.

In this paper, an attempt is made to combine the use of the anti-rotational operator and the non-linear operator of the MHD to find a self-consistent solution for the flow and the magnetic fields. The method is illustrated by an example, which shows how the magnetic field above the solar surface changes following a motion of the feet of the field lines.

A mechanism is proposed to account for the U-shaped spectrum of the type IV solar radio burst during the explosive phase of proton flare. The U-shaped spectrum consists of two parts, namely the part of type IV_μ burst and that the type IV_dm burst. Each of them is believed to be produced by gyrosynchroton radiation of nonthermal electrons (100keV ≤ ϵ ≤ 2MeV) accelerated simultaneously with protons in explosive phase and gyroresonance absorption of thermal electrons.

Numerical calculations are presented for the flux densities of type IV_μ burst and type IV_dm during 7 August 1972 event, assuming the volume of these burst sources being cylinders. It is shown that the results of numerical calculations are consistent with that of observations.

The reversal of polarized waves sense from type IV_μ burst source into type IV_dm sources is explained by the fact that the direction of the magnetic field line in one source is anti-parallel to that in the other.

Besides, we also discuss the relation between the U-shaped spectrum of type IV radio burst and the occurrence of proton event.

This paper discussed the range of applicability of the gas dynamical equations used in gas dynamical models. It is pointed out that (1), when dealing with gravitational collapse, the law of mass conservation and the equation of continuity are inapplicable if the reaction energies are large. (2) The presence of turbulence only affects the basic-state motion. If the basic-state motion is given and if we neglect higher-order small quantities and if we make certain simplifying assumptions, then the equations for small perturbations are of the same form as in the absence of turbulence. The equations used by C.C. Lin and his coworkers are precisely equations for small perturbations, hence Lin's theory still holds even if there is turbulence. If we wish to go to the next approximation, then we must, in general, take account of turbulence.

A non-conservative Lie transformation is used to establish the theory of tesseral perturbation including the cross terms from the zonal harmonic J₂ with the tesseral harmonics. The formulae for the perturbations are derived with a computer. The storage of the Poisson series is effected through a one-to-one correspondence between the multi-dimensional index of a term in the series and the store address of the coefficient of that term. Rules for storing some typical series in celestial mechanics in computers are also given.

The results of statistical analyses of the radio luminsotiy of 81 pulsars obtained in this paper appear to be in favour of the view that the radio emission originates in regions close to the light cylinder. The various statistical relations given in TABLES 1 and 2 may provide some clues on the radio emission.

We carried out a spectral analysis (by FFT and periodograms) on a homogenized set of data of coordinates of the Earth's pole in the period 1900–1969.9, and found the Chandler wobble to have 4 peaks at periods of 1.142, 1.169, 1.199 and 1.230 years. The two main peaks at 1.169 and 1.199 years have equal amplitudes (TABLE 4 and Fig. 1). According to Fedrov and Yatskiv's (1964) interpretation of sudden phase changes, our data would give a natural period of 1.184 years, but the observed asymmetry between the two secondary peaks is a difficulty for this interpretation. The observed multiplicity of peaks can also be explained by the theory of amplitude modulation, if we suppose there is a modulating oscillation with a period around 48 years. In this case, the natural period of the Chandler wobble would be 1.199 years; but this interpretation also has some difficulties.

We propose that the ascending front of a solar surge results from the ejection of plasmoid caused by the Maxwellian stresses of the reconnected field lines in the neutral current sheet above a satellite spot plus the explosive expansion of the matter inside. This model can effectively explain the main dynamical features in both the accelerating and decelerating phases during the rise of the surge.

The air density and its variations at heights near 290 km are determined from visual observations of our country's second satellite and its rocket. The relation between the sudden variations of air density and geomagnetic activity may be seen from the observed values of air density. The density increases by 75% at strong geomagnetic disturbances (Kp = 6.0). Approximately, 90% diurnal variations and 50% semiannual variations at heights near 290 km are also observed. The results are basically in accordance with the theoretical model of atmospheric density.

The conclusions reached in [1] on the permissible regions of motion in the general problem of three bodies are applied to two actual cases: Sun - Jupiter - Saturn and Sun - Neptune - Pluto. The orbital inclinations and latitudes of these planets are shown to be within the ranges of variations according to [1].