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991.
992.
Knowledge of the optical constants of elemental sulfur has potential applications to Venus, Jupiter, Io, Amalthea, and the Earth. The real part, n, of the index of refraction of liquid sulfur (at 133°C) and of solid orthorhombic sulfur (at 25°C) for the wavelength range 0.4–2.0 μm were measured ellipsometrically. The imaginary part, k, of the refractive index of liquid sulfur was obtained by transmittance measurements at the same temperature and wavelength range. The reflectance of semi-infinite slabs of solid and liquid sulfur is calculated using the measured n and k values. We confirm that sulfur melts on Io would be classified as “black” by the Voyager imaging system. 相似文献
993.
The height of the lower red border of type-B aurora has been determined by triangulation using TV cameras at two ground stations. A mean height of 91.4 ± 1.1 km was determined from a set of 12 measurements made under ideal conditions. A TV spectrograph was used simultaneously to seek possible spectral changes between 6400 and 6900 Å which would be indicative of changes in the vibrational distribution in the N2 First Positive bands. No significant difference was found in this distribution between the spectra from 93 and 122 km. The height distribution of contributions to the OI 5577 Å emission relative to the N+2 First Negative emission was modelled from 80 to 160 km. Contributions from electron impact on atomic O, O+2 dissociative recombination and N2(A)O energy transfer were included. Account was taken of recent laboratory data on O(1S) quenching. It was concluded that these processes could explain the excitation of O(1S) in normal aurora and the height distribution of OI 5577 Å in type-B red aurora. It was confirmed that the lifetime ofO(1S) in type-B red auroral rapid time variations is about 0.5 s and it was found from the model that the observed time variation can be reproduced by the mechanisms considered, provided the concentration of NO in the auroral atmosphere is about 1 × 109 at 95 km. Before reasonable certainty can be attained in the correctness of the interpretation it will however be necessary to have reliable simultaneous observations of neutral atmospheric composition particularly for O and NO as well as unchallengeable measurements of the yields of O(1S) for the processes considered and for several other processes which have been suggested recently. 相似文献
994.
Diurnal variation of the dayside, ionospheric, mid-latitude trough in the southern hemisphere at 800 km: Model and measurement comparison 总被引:1,自引:0,他引:1
J.J. Sojka W.J. Raitt R.W. Schunk J.L. Parish F.J. Rich 《Planetary and Space Science》1985,33(12):1375-1382
Our high latitude ionospheric model predicts the existence of a pronounced “dayside” trough in plasma concentration equatorward of the auroral oval in both the Northern and Southern Hemispheres for solar maximum, winter, and low geomagnetic activity conditions. The trough in the Southern Hemisphere is much deeper than that in the Northern Hemisphere, with the minimum trough density at 800 km being 2 × 103 cm−3 in the Southern Hemisphere and 104 cm−3 in the Northern Hemisphere. The dayside trough has a strong longitudinal (diurnal) dependence and appears between 11:00 and 19:00 U.T. in the Southern Hemisphere and between 02:00 and 08:00 U.T. in the Northern Hemisphere. This dayside trough is a result of the auroral oval moving to larger solar zenith angles at those universal times when the magnetic pole is on the antisunward side of the geographic pole. As the auroral ionization source moves to higher geographic latitudes, it leaves a region of declining photoionization on the dayside. For low convection speeds, the ionosphere decays and a dayside trough forms. The trough is deeper in the Southern Hemisphere than in the Northern Hemisphere because of the greater offset between the geomagnetic and geographic poles. Satellite data taken in both the Northern and Southern Hemispheres confirm the gross features of the dayside trough, including its strong longitudinal dependence, its depth, and the asymmetry between the Northern and Southern Hemisphere troughs. 相似文献
995.
N. Kameswara Rao V. R. Venugopal A. R. Patnaik 《Journal of Astrophysics and Astronomy》1987,8(3):227-230
VLA observations at 6 cm have been obtained for three hydrogen-deficient objects υ Sgr, V 348 Sgr, and A bell 58. A bell 58
was also observed at 2 cm. Only upper limits to the flux density could be set for these sources. A new radio source at 6 cm
was found in the field of υ Sgr.
The upper limit for 6 cm flux density of V348 Sgr sets an upper limit to its reddening asE(B–V) ≤ 0.65. The hydrogen deficient planetary nebula A 58 shows much lower radio flux than expected from the infrared-radio flux
density relationship of planetary nebulae.
National Radio Astronomy Observatory’s Very Large Array is operated by Associated Universities Inc. under contract with National
Science Foundation, USA. 相似文献
996.
B. Caccin A. Donati-Falchi R. Falciani L. A. Smaldone G. P. Tozzi 《Solar physics》1987,112(2):383-386
Using the method of solar bidimensional spectroscopy based on the Universal Birefringent Filter (UBF), we have determined the bidimensional maps of moments of some chromospheric lines. The observational material, referring to a quiet region on the disk center, have been acquired with the UBF of the NSO at Sacramento Peak on Aug. 27,1985. In this note we present the work in progress and the new observational aspects arising from this diagnostic method.Visiting astronomers at the National Solar Observatory/Sacramento Peak, operated by the AURA under contract with the NSF 相似文献
997.
R. F. Griffin 《Journal of Astrophysics and Astronomy》1988,9(4):205-211
Photoelectric radial-velocity measurements show that HD 116093 is a double-lined spectroscopic binary in a very eccentric
53-day orbit. Very little else is known about the system, but circumstantial evidence is consistent with the hypothesis that
the components’ types are near to F3 V and F8 V. If that is so, the orbit must be seen very nearly edge-on; a search for eclipses
is warranted and an ephemeris for them is given. 相似文献
998.
999.
A method is described for reconstructing the true geometry of a solar loop observed on the disk which takes account of tilt in its own plane. Reconstructions of three H loops yield small tilt angles (14°) and provide further evidence that H loops show a close correspondence to the field lines of a magnetic dipole. The method offers new opportunities for exploring the physics of individual solar loops. 相似文献
1000.
The flux emitted by Titan's disk in millimeter lines of HCN, HC3N, CH3CN, and CO is calculated by means of a radiative transfer formulation which takes into account the sphericity of the atmosphere. It is demonstrated that the plane-parallel approximation for radiative transfer is no longer valid, especially in the core of emission lines, when Titan is not spatially resolved. The antenna temperatures which would be measured by large radiotelescopes observing Titan at frequencies of (1?0) and (2?1) transitions of CO, of (1?0), (2?1), and (3?2) transitions of HCN, and of selected transitions of HC3N and CH3CN in the range 80–300 GHz are calculated. The observability of these transitions is investigated. It is concluded that there is the possibility of inferring the vertical stratospheric distribution of these species from line shape measurements to be achieved with existing or forthcoming radioastronomical instrumentation. The determination of the CO abundance by D. O. Muhleman, G. L. Berge, and R. T. Clancy (1984, (Science (Washington, D.C.), 223, 393–396) from measurements at 115.3 GHz in two 200 MHz bands, is reinterpreted by means of this radiative transfer formulation. A CO mixing ratio between 3 × 10?5 and 18 × 10?5, with a most plausible value of 7.5 × 10?5, is found. 相似文献