Optical thickness of the Cassini division     

K.A. Hämeen-Anttila 《Icarus》1977,31(3):385-400

Various estimates for the optical thickness of the Cassini division are studied in order to explain and eliminate the discrepancies between them. An analysis of dark-side observations and a theoretical study based on the behavior of collisions suggest that the optical thickness of the Cassini division is not constant, but fluctuates in the range of 10^?4–10^?3. The nonzero brightness in reflected light is caused either by stray light or by narrow optically thick ringlets inside the Cassini division.  相似文献   

The polarization of the inner solar corona at the eclipse of 10 July 1972     

G. M. Nikolsky  A. A. Sazanov  A. K. Kishonkov 《Solar physics》1977,53(1):79-96

Photographs of the corona in the continuum spectrum (580–700 nm) have been obtained with a doublet camera (F=4m) through rotating sector polarizers with the vibrational directions oriented radially and tangentially to the solar limb. Isophotes of the total emission and its polarized component, as well as diagrams giving the degree of polarization for the (K+F)-corona and the electron corona proper (P _K), have been plotted up to the distance of 1R from the limb. In some inner regions the polarizationP _K exceeds the highest value possible for Thomson scattering under the given conditions. The reality of this anomally is dubious; systematic photometrical errors may account for it. Three-dimensional forms of 15 different coronal rays have been ascertained by comparing the course of polarization along the rays to the family of Baumach curves. The rays are found to deflect substantially from the radial directions out of the plane of the sky. Mean values of the coronal brightness and polarization versus the distance from the Sun have been determined. Contrary to well-known models (Van de Hulst) the mean polarization of the electron corona (P _K) decreases with distance after reaching the maximum (50%) at (1.4–1.6)R from the Sun's centre. This decrease can be explained by deflection of the streamers from radial directions.  相似文献   

A model for thinning of the plasma sheet     

J.K. Chao  J.R. Kan  A.T.Y. Lui  S.-I. Akasofu 《Planetary and Space Science》1977,25(8):703-710

A one-dimensional model for thinning of the plasma sheet is developed on the basis of launching a fast mode MHD rarefaction wave propagating in the tailward direction along the plasma sheet. Behind the rarefaction wave the pressure is reduced, leading to thinning of the plasma sheet and also to an Earthward plasma flow with a speed on the order of the sound speed a₀. The plasma sheet thickness is reduced by a factor of 2 if an Earthward plasma flow speed of 0.8a₀ is induced. The predictions of the model are in reasonable agreement with observations.  相似文献   

Generalized polytropes: Stellar structure with a boltzmann factor     

D. K. Callebaut  N. Van Den Bergh  M. Verbruggen 《Astrophysics and Space Science》1982,86(2):397-417

In order to study the structure of a chemically homogeneous star in equilibrium, a density profile of the form T ^N exp(–µm(–)/kT) is suggested. As for polytropes, qualitative aspects of the resulting stellar model can be discussed analytically. In particular it is shown that one reobtains forN=3 Eddington's standard model, whereas forN<3 nearly polytropic models result. WhenN>3, the effective polytropic index does vary appreciably over the star. Numerical results indicate that the proposed density profile is quite reasonable in view of the simplicity of the model. From a comparison of the degree of precision of a polytropic approximation with that of the newly proposed model it follows that the new approximation is definitely better than the polytropic one. It is suggested that the model may be useful to study the structure of stellar clouds, clusters and (spherical) galaxies.Now at Department of Applied Mathematics, Queen Mary College, University of London, England.  相似文献   

An upper limit on the aperture separation of ion drift meters     

E. A. Bering  K. G. Weber  U. V. Fahleson 《Astrophysics and Space Science》1982,83(1-2):37-49

An upper limit has been calculated on the effective aperture separation or detector thickness of ion drift meters of two fundamental types. The limit applies to meters which compare currents collected by detectors with different view directions at the same retarding potential and to meters which measure the entire thermal ion distribution function. For both types, a single scanned detector may be employed instead of multiple detectors, in which case the limit applies to twice the radius of curvature of the path followed by the detector aperture during a scan, (i.e. the diameter of a spinning payload). The limit was found to be important in two cases. First, in the F region on spacecraft with stringent electrostatic cleanliness requirements, the 10% error limit was found to be 40 cm. Second, in the E region, the limit was found to be 1 cm.Originally submitted to the journalSpace Science Instrumentation.Deceased.  相似文献   

Light curves of SZ Piscium for 1977 and 1978     

Joel A. Eaton  Franco Scaltriti  M. Cerruti-Sola  M. B. K. Sarma  B. D. Ausekar  Santo Catalano  Marcello Rodono 《Astrophysics and Space Science》1982,82(2):289-306

We present a relatively completeV-band light curve of SZ Psc for 1978 and a partial light curve for 1977. From the 1978 light curve we derive a new time of primary minimum, JD2443823.674±0.001, and a Russell-model solution,i=75°.8±0°.1,r _h =0.096±0.003,r _c =0.351±0.001, andL _h =0.253±0.002. The hotter component of this system is a F5-8 main-sequence star, the cooler component a K3-4 star well above the main sequence. The system is detached with the larger component filling only 82% of its Roche lobe. The distortion wave in this RS CVn-type binary seems not to migrate regularly as do those in many other such systems, but rather seems to change phase and amplitude more erratically. Between 1977 and 1978 its phase stayed practically constant while its amplitude decreased by a factor of three. We discuss the implications of this behavior for the spot model of RS CVn-type activity. We find that the traditional comparison star for SZ Psc, HD 219018, is very likely a constant star contrary to a recent suggestion that it is variable. Its brightness and colors,V=7.705, (B-V)=0.628, and (V-I) _c =0.688, are those of a G2V star.Visiting Astronomer, Kitt Peak National Observatory, which is operated by AURA, Inc., under contract with the National Science Foundation, and Visiting Astronomer, Prarie Observatory, University of Illinois.  相似文献   

Cosmological molecular hydrogen and the distortion of the relict radiation spectrum     

V. K. Khersonskii 《Astrophysics and Space Science》1982,88(1):21-30

The distortions of the relict radiation spectrum in the region of the wavelength <120 are considered. These distortions are due to the emission of photons under the formation of molecular hydrogen in the expanding universe in the cosmological epoch 40z200. It is shown that the real intensity of the relict radiation in the region of the wavelength under consideration must significantly exceed Planck's intensity, with a radiation temperature amounting to 2.8 K.  相似文献   

Massive configurations with constant densities     

M. C. Durgapal  A. K. Pande  K. Pandey 《Astrophysics and Space Science》1982,88(2):469-475

Two new classes of solutions with constant observed proper and rest mass densities are described. Unlike the well-known solution of constant coordinate mass density, these solutions pertain to realistic physical situations. For these solutions, the various relevant parameters, viz. the redshifts (dP/d)₀ and binding coefficients have been calculated.  相似文献   

Distribution of sunspots according to their magnetic fluxes     

T. K. Das  M. K. Das Gupta 《Solar physics》1982,78(1):67-70

The occurrence frequency distribution of sunspots in different magnetic flux values has been examined. The number of sunspots decreases as ^-1.9 for sunspots with magnetic flux greater than 3 × 10²¹ Maxwell, where is the said flux of a sunspot.  相似文献   

Vector magnetic field evolution,energy storage,and associated photospheric velocity shear within a flare-productive active region   总被引：1，自引：0，他引：1  

K. R. Krall  J. B. Smith Jr.  M. J. Hagyard  E. A. West  N. P. Cummings 《Solar physics》1982,79(1):59-75

The evolution of vector photospheric magnetic fields has been studied in concert with photospheric spot motions for a flare-productive active region. Over a three-day period (5–7 April, 1980), sheared photospheric velocity fields inferred from spot motions are compared both with changes in the orientation of transverse magnetic fields and with the flare history of the region. Rapid spot motions and high inferred velocity shear coincide with increased field alignment along the B _L= 0 line and with increased flare activity; a later decrease in velocity shear precedes a more relaxed magnetic configuration and decrease in flare activity. Crude energy estimates show that magnetic reconfiguration produced by the relative velocities of the spots could cause storage of 10³² erg day^–1, while the flares occurring during this time expended 10³¹ erg day^–1.Maps of vertical current density suggest that parallel (as contrasted with antiparallel) currents flow along the stressed magnetic loops. For the active region, a constant-, force-free magnetic field (J = B) at the photosphere is ruled out by the observations.Presently located at NASA/MSFC, Huntsville, Ala. 35812, U.S.A.  相似文献