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1.
Synoptic photoelectric observations of the coronal Fexiv and Fex emission lines at 530.3 nm and 637.4 nm, respectively, are analyzed to study the rotational behavior of the solar corona as a function of latitude, height, time and temperature between 1976 (1983 for Fex) and 2001. An earlier similar analysis of the Fexiv data at 1.15 R
over only one 11-year solar activity cycle (Sime, Fisher, and Altrock, 1989, Astrophys. J.
336, 454) found suggestions of solar-cycle variations in the differential (latitude-dependent) rotation. These results are tested over the longer epoch now available. In addition, the new Fexiv 1.15 R
results are compared with those at 1.25 R
and with results from the Fex line. I find that for long-term averages, both ions show a weakly-differential rotation period that may peak near 80° latitude and then decrease to the poles. However, this high-latitude peak may be due to sensing low-latitude streamers at higher latitudes. There is an indication that the Fexiv rotation period may increase with height between 40° and 70° latitude. There is also some indication that Fex may be rotating slower than Fexiv in the mid-latitude range. This could indicate that structures with lower temperatures rotate at a slower rate. As found in the earlier study, there is very good evidence for solar-cycle-related variation in the rotation of Fexiv. At latitudes up to about 60°, the rotation varies from essentially rigid (latitude-independent) near solar minimum to differential in the rising phase of the cycle at both 1.15 R
and 1.25 R
. At latitudes above 60°, the rotation at 1.15 R
appears to be nearly rigid in the rising phase and strongly differential near solar minimum, almost exactly out of phase with the low-latitude variation. 相似文献
2.
Main results of computations of evolution for massive close binaries (10M
+9.4M
, 16M
+15M
, 32M
+30M
, 64M
+60M
) up to oxygen exhaustion in the core are described. Mass exchange starting in core hydrogen, shell hydrogen and core helium burning stages was studied. Computations were performed assuming both the Ledoux and Schwarzschild stability criteria for semiconvection. The influence of UFI-neutrino emission on evolution of close binaries was investigated. The results obtained allow to outline the following evolutionary chain: two detached Main-Sequence stars — mass exchange — Wolf-Rayet star or blue supergiant plus main sequence star — explosion of the initially more massive star appearing as a supernova event — collapsed or neutron star plus Main-Sequence star, that may be observed as a runaway star — mass exchange leading to X-rays emission — collapsed or neutron star plus WR-star or blue supergiant — second explosion of supernova that preferentially disrupts the system and gives birth to two single high spatial velocity pulsars.Numerical estimates concerning the number and properties of WR-stars, pulsars and X-ray sources are presented. The results are in favour of the existence of UFI-neutrino and of the Ledoux criterion for describing semiconvection. Properties of several well-known X-ray sources and the binary pulsar are discussed on base of evolutionary chain of close binaries. 相似文献
3.
We observed Faraday rotation of linearly polarized radio waves from the Crab Nebula (Tau A) at 4170 MHz during solar coronal occultations in June 1971–75. Mean amplitudes of the variations of position angle are larger in an active phase of the solar cycle than in a quiet phase. In occultations in 1971 and 1973, the position angle of the polarization varied oscillatory by 20–50 degrees due to local magnetic structures in the corona with a typical scale-length of about 0.5 R
. In 1974, we observed a typical variation of position angle of polarization which is expected from a Y-shaped field configuration in coronal streamers.The Faraday rotation is enhanced when the line of sight to Tau A passes through strong coronal magnetic fields computed from magnetograph observations, while the rotation is suppressed when the line of sight passes through large coronal holes observed in X-rays. Short-time oscillation of the rotation angle observed in 1971 and 1973 suggests that neutral sheets in coronal streamers oscillate at a period of 3 hours with an amplitude of 1 R
at a distance of 10 R
from the Sun. 相似文献
4.
We present observations of Ovi 1032 Å line profiles obtained with the SUMER instrument on SOHO extending from the solar disk to 1.5 R
above the limb in the north polar coronal hole. Variations of the intensity and linewidth in the polar plume and inter-plume regions are investigated. We find an anti-correlation between the intensity and the linewidth in the plume and inter-plume regions with detailed plume structures been seen out to 1.5 R
. Possible implications regarding the magnetic topologies of these two regions and related heating mechanisms are discussed. The Ovi linewidth measurements are combined with UVCS output to provide an overview of its variations with height extending up to 3.5 R
. We find a linear increase of the linewidth from 1 to 1.2 R
, then a plateau followed by a sharp increase around 1.5 R
. 相似文献
5.
The analysis of a storm of type III solar radio bursts observed in August 1968 between 5 and 0.2 MHz by the RAE-1 satellite has yielded the storm morphology, a possible relation to meter and decameter storms, and an average exciter speed of 0.37 c between 10 and 40 R
(Fainberg and Stone, 1970a, b). A continuation of the analysis, based on the apparent dependence of burst drift rate on heliographic longitude of the associated active region, now provides a distance scale between plasma levels in the streamer, an upper limit to the scale size of coronal streamer density inhomogeneities, and an estimate of the solar wind speed. By fixing one level the distance scale is utilized to determine the electron density distribution along the streamer between 10 and 40 R
. The streamer density is found to be 16 times that expected for the solar minimum quiet solar wind. An upper limit to the scale size of streamer density inhomogeneities is estimated to be of the order of 1 or 2 solar radii over the same height range. From the progressive delay of the central meridian passage (CMP) of the lower frequency emission, a streamer curvature is inferred which in turn implies an average solar wind speed of 380 km/sec between 14 and 36 R
within the streamer. 相似文献
6.
The published photometric and spectroscopic data of the symbiotic binary V 1329 Cyg are interpreted. It is shown, that V 1329 Cyg is an eclipsing binary with an elliptical orbit orbit (e=0.28). The cooler component fills up the Roche-lobe at periastron. A model of moving gaseous structures in the system is proposed and their influence on the radial velocity curve is shown. The following characteristics of the system are derived: the cooler component is an M6 giant with mass 7.9M
, radius 339R
and luminosityM
bol=–5.42, the hot component is a white dwarf surrounded by an accretion disk. The mean distance between the components is 842R
and in periastron it decreases to 605R
. 相似文献
7.
Relativistic, isentropic, homogeneous models are constructed by a method that automatically detects instabilities, and evolutionary tracks of central conditions are shown on a (T, ) diagram. Models heavier than 20M
become unstable because of pair creation. Iron photodisintegration causes instability in the mass range between 1.5M
and 20M
. General relativistic effects bring about the onset of instability in models of 1.2–1.5M
when the central density is about 1010 g/cm3. Lighter models become white dwarfs. It is pointed out that general relativistic instability will prevent the formation of neutron stars through hydrostatic evolution and may be relevant in setting off low-mass supernovae. 相似文献
8.
The principal polar-crown coronal helmet structures were selected from nearly three years (May, 1965–January, 1968) of K-coronameter observations made at Haleakala and Mauna Loa, Hawaii. Six isolated and long-lived helmet systems were found at latitudes of 45° and above. Their developments are compared with underlying chromospheric and photospheric activity and a simple phenomenological model is presented showing that a coronal system is formed over an active region. Thereafter the center of gravity of the system gradually drifts poleward with the trailing unipolar magnetic region (UMR), and it becomes a high latitude coronal helmet, arched over a polar crown filament.By comparison of these coronal helmets with observations of the outer corona (to circa 4 R
) made at solar eclipse, lunar sunset, and with balloon and rocket-borne externally occulted corona-graphs, it appears that ground-based K-coronameter measurements to a distance of 1.5–2.0 R
are sufficient to detect the coronal streamers.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
9.
The brightness distribution of the quiet Sun at 8.6 mm wavelength is synthesized from off-meridian observations using an eight element east-west interferometer with a maximum base line of 16.38 m (1913). The observed brightness distribution is practically flat from the disk center to the optical limb. The effective radius of the nearly uniform component is 1.01 R
. If the limb brightening is present, the brightening located between 0.95 R
and 1.01 R
, and the total flux density of the limb brightening is less than 1% of the total flux density of the Sun. In addition to the nearly uniform component there exists a coronal component just outside the optical limb. 相似文献
10.
In this paper we consider effects of the general relativity and an accreting black hole in a globular cluster by studying the evolution of a globular cluster core as a whole, i.e., without the partition of the core into the so-called cusp and isothermal core regions. The globular cluster core is assumed to contain a massive black hole at its center. We show that the final fate of the evolution of a globular cluster core depends on the mass of the black hole at its center. When the massM of the black hole is greater than 3×103
M
, there will be a contraction of the core. On the other hand, if the mass of the black hole is smaller (102
M
M3×103
M
) in the center, the core will expand until complete dissolution. 相似文献
11.
A. C. Riddle 《Solar physics》1970,13(2):448-457
The 80 MHz emission from a moving type IV source has been observed as the source moved from 2 to 51/4 R
from the centre of the Sun. The emission came from a plasma cloud ejected in association with an extensive solar prominence. The cloud appeared to move with a speed ( 270 km/sec) approximating the local Alfvén velocity in the corona. At 2 R
the emission was from a single unpolarized source, while at 5 R
it was from two sources strongly circularly polarized in opposite senses. The physical conditions inside and outside the source and the emission mechanisms are discussed. 相似文献
12.
Jagdev Singh 《Solar physics》1985,95(2):253-262
The line and continuum intensities deduced from the multislit spectra of the (Fe X) coronal emission line taken at the 1980 eclipse are used to discuss the relative roles of radiative and collisional excitation mechanisms. It is shown that for R/R
< 1.2, collisional excitation is the predominant mode. Collisional as well as radiative excitation is equally important for 1.2 < R/R
< 1.4, whereas beyond 1.4 R
radiative excitation becomes dominant. The line width measurements indicate that a large number of locations have half-widths around 1.3 Å. The maximum half-width is reached at 1.4 R
with an average value of 1.6 Å. 相似文献
13.
Using new close-coupling excitation rates for the C-like ion Siix, density-diagnostic ratios based on Siix lines have been re-evaluated and applied to a sequence of CDS observations taken above a polar coronal hole. The derived electron densities are in excellent agreement with previous values of Neestimated from the N-like ion Siviii for another coronal hole. The confirmed trend is for a fall-off of one order of magnitude within the first 0.3 Rabove the limb. These densities are well fitted with an analytic formula for the density profile out to at least 8 R, by which stage the electron density has fallen to 4×103 cm–3, from 1.5×108 cm–3at 1.0 R. 相似文献
14.
The radial brightness distribution of the quiet Sun at 8.6 mm is synthesized from observations using a sixteen element east-west interferometer in Nagoya. The observed brightness is flat from the disk center to 0.8R
. A slight darkening appeared between 0.8R
and the limb. No evidence of the bright ring near the limb is found. The radio radius at 8.6 mm is 1.015±0.005R
. In addition there exists a coronal component just outside the radio limb. 相似文献
15.
C. F. Keller 《Solar physics》1971,21(2):425-429
White-light photographs of the solar corona were taken during the March 1970 eclipse from an Air Force NC-135 jet aircraft at an altitude of 36 380 ft. Four photographs each were made for several exposure times varying from 0.1 to 10.0 s. Three each were made with plane polaroid filters whose orientation was varied at 60° intervals. Stabilization of the camera was approximately 10 even during the longest exposures. The corona was recorded to distances beyond 12 R
.A preliminary study of per cent polarization as a function of position with respect to the solar disk for a set of 1.0 s exposures shows an inversion in per cent polarization in the region 6 to 8 R
-polarization decreasing outward to the region and increasing again beyond it. This inversion is most apparent along the major streamers.Intensities traced outward from the Sun in both polar and equatorial directions are compared with previous observations.Work done under the auspices of the U.S. Atomic Energy Commission. 相似文献
16.
We show that within distances from the Sun's surface less than the height of a streamer helmet, each of two neighboring rays of the streamer belt, as they approach the solar surface, bends around the helmet on either side of it. Also, a minimum angular diameter of the rays of d2°–3° remains virtually constant within R=1.2–6.0 R
. A density inhomogeneity (`blob') can be produced above the helmet top visible to at least R6 R
. In this case the initial velocity of the `blob' increases with solar distance from where it is generated to something like the velocity of the bulk solar wind with which the `blob' is carried away. 相似文献
17.
Robert L. Oldershaw 《Astrophysics and Space Science》2001,278(4):425-432
Mass functions for samples of white dwarf stars and for a largeheterogeneous sample of nearby stars appear to have unexplained deficitsin the 0.70 M
to 0.75 M
range. The existence, ornon-existence, of this anomaly constitutes a definitive test of afractal cosmological model that inherently predicts a gap in stellarmass functions at 0.73 M
. 相似文献
18.
Observations are presented of emission line resonance polarization in Fe xiii 10747 at the total solar eclipse of 12 November 1966. Useful data, with angular resolution 15, describe three quadrants of the corona from 1.08 R
to a maximum of 1.6 R
. The direction of the electric vector of observed polarization is perpendicular to the solar limb, to the limits of accuracy of measurement, in at least 74% of all cases. Departures in the other points are consistent with the magnetic depolarization expected from the non-radial fields of streamers. Polarizations observed range from near zero at the limb to 80 % and higher at 1.6 R
. Averaged polarization is highest in non-streamer regions, where above 1.2 R
it suggests pure radiative excitation of the 10747 line. Below 1.2 R
, and in a dense streamer, the polarization is significantly depressed, indicating dominant collisional excitation of the line wherever the electron density exceeds 50 × 106 cm–3.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
19.
C12 stars in the range 1.04–1.55M
are evolved to simulate the core evolution of the possible precursors of planetary nebulae. The nuclear shell burning in stars above 1.2M
advances to within about 0.2M
of the surface, where the intense radiation interacts with the surface matter and causes mass loss. Comparison between our theoretical results and observations suggests that this may be a mechanism by which planetary nebulae are formed.Presented at the Trieste Colloquium on Mass Loss from Stars, September 12–16, 1968. 相似文献
20.
Shiv S. Kumar 《Astrophysics and Space Science》1972,17(1):219-222
It is suggested that the minimum mass of a star at the time of its formation is approximately 0.01M
. Making use of this fact and the stellar mass functionF(M) M
–, it is found that the hidden mass (or the missing mass) in the solar neighborhood may be explained by the presence of a large number of invisible stars of very low mass (0.01M
M<0.07M
). 相似文献