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961.
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
962.
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
963.
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
964.
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:
- 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.
- 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).
- In the future the negative flares around 8000 Å should be looked for in early-type flare stars of types M0-K5.
- For a positive discovery of negative flares, future observations must be carried out in the wavelength region of 1–3 μm.
965.
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
966.
High-resolution spectroscopic observations of asteroids Ceres and Pallas have been obtained in the 1.0- to 2.6-μm region. Combined with previous spectralmeasurements at other wavelengths, this work presents the broadband spectral reflectances of these asteroids over the 0.4 to 3.6-um region. This extended coverage permits new analyses of the surface mineralogies of these objects. Using laboratory comparison spectra of meteorites and mixtures of terrestrial minerals, the surfaces of Ceres and Pallas are consistent with mixtures of opaques and hydrated silicates, such as are found in types C1 and C2 meteorites. This research emphasizes the importance of the 3-um spectral region for studying by remote methods the relationship of carbonaceous chondrite mineralogies to asteroid surfaces. 相似文献
967.
Spectropolarimetry of Jupiter at resolutions between 22 and 35 Å reveals a strong increase of linear polarization in the 7250- CH4 band. This is very probably due to the decreasing contribution toward the band center of the higher orders of scattering, which have a smaller net polarization than the first few orders. The linear polarization is also enhanced in the band at 7900 comprising the 7920- NH3 and 7600- to 8200- CH4 bands. The normalized circular polarization shows a feature at 7250 with a dispersion shape. This is most probably produced in a double-scattering process involving either a solid or liquid aerosol with an absorption at 7250 . Methane aerosols, the obvious candidates from a spectroscopic point of view, are, however, forbidden if current estimates of the Jovian atmospheric temperature are correct. 相似文献
968.
In March 1977 an unmanned ELF/VLF goniometer receiving station was deployed on the Antarctic plateau 110 km south south west of the British Antarctic Survey base at Halley. A UHF Telemetry link enabled the ELF and VLF signals to be monitored and recorded at Halley, simultaneously with data from an identical ELF/VLF receiver at Halley. The remote station was designed for unattended operation with a wind driven generator to recharge its battery. Design considerations and problems encountered are discussed and some preliminary results are presented. 相似文献
969.
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
970.
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