Oscillations of the Hα emission in solar prominences     

E. Wiehr  G. Stellmacher  H. Balthasar 《Solar physics》1984,94(2):285-288

The time dependence of Doppler shift and line-center intensity is simultaneously observed for the H emission of three solar prominences, each one during about two hours. Doppler oscillations with periods near one hour and amplitudes between 1 and 2 km s^–1 are conspicuously visible in the recordings of all three prominences. Fourier analysis yields periods of 50, 60, and 64 min, as well as slight indications of short periods near 3 and 5 min. No oscillations are found in the line-center brightness.  相似文献   

Radar observations of asteroid 1580 Betulia     

Gordon H. Pettengill  Steven J. Ostro  Irwin I. Shapiro  Brian G. Marsden  Donald B. Campbell 《Icarus》1979,40(3):350-354

Radar observations of the asteroid 1580 Betulia, made at a wavelength of 12.6 cm, show a mean radar cross section of 2.2 ± 0.8 km² and a total spectral bandwidth of 26.5 ± 1.5 Hz. Combining our bandwidth measurements with the optically determined rotation period sets a lower limit to the asteroid's radius of 2.9 ± 0.2 km.  相似文献   

On the influence of mass loss and convective overshooting on the evolution of massive stars     

A. G. Massevitch  E. I. Popova  A. V. Tutukov  L. R. Yungelson 《Astrophysics and Space Science》1979,62(2):451-463

Evolution of massive stars losing mass with the rateM H L/V C is computed (for =1,2,7). It is shown that observed mass loss rates correspond to 0.3 and, therefore, mass loss by stellar wind cannot play any significant role in the evolution of normal massive stars. However, for several types of massive stars (WR, OH/IR, X-ray sources) enhanced mass loss explains their peculiar features. Computations of evolutionary sequences of massive stars with convective overshooting taken into account (as a formal increase of the convective core) show that a significant broadening of the hydrogen-burning band in the H-R diagram may be obtained.  相似文献   

On the infrared observations of stellar flares     

G. A. Gurzadyan 《Astrophysics and Space Science》1979,62(1):45-53

In connection with the appearance of the first results of infrared observations of stellar flares, a more elaborate analysis ofnegative infrared flares as a phenomenon, predicted by the fastelectron hypothesis, has been carried out. As a result, the wavelength regions of negative flares are established for the stars of different spectral types as well as the calculated amplitudes of the negative flares (Tables I and II). The analysis of the infrared observations (c.f. Kilyachkoet al., 1978) lead to the following conclusions:

1. The negative infrared flares discovered around 8000 Å is not in agreement with the theory in the case of the flare star UV Cet. Some traces of negative flares have been noted for a number of less powerful flares of EV Lac.
2. The amplitudes of the recorded positive flares of UV Cet and EV Lac on λ8000 Å are in good agreement with the magnitudes predicted by the fast-electron hypothesis (non-thermal bremsstrahlung).
3. In the future the negative flares around 8000 Å should be looked for in early-type flare stars of types M0-K5.
4. For a positive discovery of negative flares, future observations must be carried out in the wavelength region of 1–3 μm.

  相似文献   

Uranus: Disk structure within the 7300-Å methane band     

Michael J. Price  Otto G. Franz 《Icarus》1979,39(3):459-472

Orthogonal narrow-band (100 Å) photoelectric slit scan photometry of Uranus has been used to infer the basic two-dimensional structure of the disk within the 7300-Å methane band. Numerical image reconstruction and restoration techniques have been applied to quantitatively estimate the degrees of polar and limb brightening on the planet. Through partial removal of atmospheric smearing, an effective spatial resolution of approximately 0.9 arcsec has been achieved. Peak polar, limb, and central intensities on the disk are in the respective proportions 3:2:1. In addition, the bright polar feature is displaced from the geometric pole towards the equator of the planet.  相似文献   

Thermal balance of the mid-latitude F2-region at night     

G.J. Bailey  R.I. Footitt  R.I. Moffett 《Planetary and Space Science》1979,27(8):1063-1073

The thermal balance of the plasma in the night-time mid-latitude F2-region is examined using solutions of the steady-state O⁺ and electron heat balance equations. The required concentrations and field-aligned velocities are obtained from a simultaneous solution of the time-dependent O⁺ continuity and momentum equations.The results demonstrate the systematic trend for the O⁺ temperature to be 10–20 K greater than the electron temperature during the night at around 300 km, as observed at St. Santin by Bauer and Mazaudier. It is shown that frictional heating between the O⁺ and neutral gases is the cause of the O⁺ temperature being greater than the electron temperature; the greater the importance of frictional heating in the thermal balance the greater is the difference in the O⁺ and electron temperatures. A study is made of the roles played in the thermal balance of the plasma by the thermal conductivity of the O⁺ and electron gases; collisional heat transfer between O⁺ electrons and neutrals; frictional heating between the O⁺ and neutral gases; and advection and convection due to field-aligned O⁺ and electron motions. The results of the study show that, at around 300 km, electron cooling by excitation of the fine structure of the ground state of atomic oxygen plays a major role in the thermal balance of the electrons and, since the temperature of the ions is little affected by this electron cooling process, in determining the difference between the ion and electron temperatures.  相似文献   

Temperature domains in the ionosphere     

A.B. Shvartsburg  V.G. Korobeinikov  M.G. Deminov  A.V. Razmadze 《Planetary and Space Science》1979,27(2):159-163

The non-linear stationary temperature waves (domains) is analysed. The exact analytical solutions of the non-linear equation of the heat conductivity determine the region of existence of such domains and the critical values of plasma parameters, correspond to the increase of the periodical temperature profiles in the plasma. A stationary source of heating (photo-electrons or electric fields) may stimulate the existence of domains, when the power of the source reaches a critical value. Conditions in the F-region of the ionosphere near the equator favour the increase of the domains.  相似文献   

Spectroscopic observations of winds on Venus: I. Technique and data reduction     

A.T. Young  R.A. Schorn  L.D.G. Young  D. Crisp  E.S. Barker 《Icarus》1979,38(3):435-450

We present out methods of measurement and reduction of high-dispersion photographic spectra of Venus. Our preliminary results are consistent with slow direct or no rotation at the level we sample, and disagree strongly with a 4-day retrograde rotation. A serious systematic error, which affects much published work, is due to blending of solar lines in the sky with those reflected from the planet. This always tends to produce a spurious retrograde “rotation.” Only data obtained in a dark sky, or daytime observations from which the sky lines have been accurately subtracted, can be relied upon. All such data give low wind speeds.  相似文献   

Collision frequency and transport properties of electrons in the ionosphere     

K.M. Aggarwal  Nardsder Nath  C.S.G.K. Setty 《Planetary and Space Science》1979,27(6):753-768

A unified ionospheric electron collision frequency model profile 〈ν_g〉 has been calculated in the height range 50–500 km. The computed profile accounts for the electron collisions with the neutral particles as well as the ions. Experimental values of momentum transfer cross-sections have been used for electron collisions with N₂, O₂ and Ar and theoretical values for N, O, He and H. It is observed that the electron-ion collisions 〈ν_ei〉 dominate over the electron-neutral collisions 〈ν_en〉 above 170 km. However, 〈ν_e?N〉 is of the same order of magnitude as 〈ν_e?O〉 in the height range 170–210 km. Above 360 km 〈ν_e?O〉 becomes more important among the neutrals. The temporal, seasonal and solar epoch variations of 〈ν_ei〉 are also shown. A typical electron collision frequency profile 〈ν_g〉 corresponding to the exospheric temperature of 1100 K has been compared with the available experimental results for D, E and F-regions obtained from different experimental techniques. This profile has been used to determine the electrical, thermal, heat flow and current flow conductivities, the mobility and the diffusivity of electrons. The results so obtained are found to be in good agreement with the earlier results.  相似文献   

The excitation of ionic lines and molecular bands in meteor wakes     

L.M.G. Poole 《Planetary and Space Science》1979,27(1):59-61

The appearance of multiplets arising from the 4²P state of CaII (the H and K lines and an infrared triplet), the 1st positive band of N₂ and possibly certain multiplets of FeII in meteor wake spectra is explained semi-quantitatively in terms of the two-step sequence: collisional ionization of major atmospheric species O₂ and N₂ followed by resonant charge exchange with ablated meteoric atoms. Many other features which could arise through this mechanism (multiplets of MgII, SiII and FeII, and bands of O₂ and N₂) are likely to be weak or to have escaped detection owing to observational selection.  相似文献