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1.
Patrick C. Crane 《Solar physics》1998,177(1-2):243-253
Fourier analysis (DFT/CLEAN) of the international sunspot number (R) series since 1932 has revealed two long (250–500 days) and distinct episodes of solar activity exhibiting persistent 13 -day variations. The first episode lasts 500 days near the maximum of solar cycle 20, and the second, 250 days near the end of the current solar cycle 22. The solar radio flux density (F
10_7cm) series since 1947 has also been analyzed. During the first episode both solar indices exhibit distinct 27- and 13-day variations (the first report of 13-day variations in F
10_7cm). During the second episode neither index exhibits distinct 27-day variations and only R exhibits 13-day variations. Conditions affecting the appearance of 13-day variations in F
10_7cm are discussed. 相似文献
2.
A detailed investigation of the evolution of low-mass binaries is performed for the case when the secondary fills its Roche lobe at the stage of core hydrogen exhaustion. The obtained results are compared with observational data for ultra-short periodic X-ray systems MXB 1820-30 and MXB 1916-05. In the frame of the proposed evolutionary scenario it is possible to obtain for MXB 1820-30 its periodP=11.4 min twice (see Figure 2). In the first case the parameters of the system are:M
2 0.13–0.15M
,X0.05–0.13, |P/P| (3.6–6.2) } 10–7 yr–1, M2 (4.1–9.6) } 10–9
M
yr–1, for the second:M
2 0.08–0.09M
,X= 0, |P/P| (1.3–1.5) } 10–7 yr–1, M2 (1.4–1.8) } 10–8
M
yr–1. It is suggested that MXB 1916-05 is the progenitor of the system MXB 1820-30 (M
2 = 0.1M,X 0.221,M
2 1.8 × 10–10
M
yr–1). 相似文献
3.
We study the effects of the sector structure of the interplanetary magnetic field (IMF) on the Galactic cosmic ray (GCR) anisotropy at solar minimum by using Global Network neutron monitor data. The hourly neutron monitor data for 1976 were averaged for the positive (+) and negative (–) IMF sectors (+ and – correspond to the antisolar and solar directions of magnetic field lines, respectively) and then processed by the global survey method. We found that the magnitude of the GCR anisotropy vector is larger in the positive IMF sector and that the phase shifts toward early hours. The derived GCR components A
r, A
, and A
for the different + and – sectors are then used to calculate the angle ( 46°) between the IMF lines and the Sun–Earth line, the solar wind velocity U ( 420 km/s), the ratio of the perpendicular (K
) and parallel (K
||) diffusion coefficients K
/K
|| = ( 0.33), and other parameters that characterize the GCR modulation in interplanetary space. 相似文献
4.
Werner Lohmann 《Astrophysics and Space Science》1976,41(1):27-37
Zusammenfassung Der offene Sternhaufen NGC 5617 wurde nach dem Streifenverfahren auf Karten von photographischen Aufnahmen verschiedener Belichtungszeiten mit dem 1m-Schmidt-Teleskop des European Southern Observatory in Chile untersucht. Der Haufen enthält etwa 460 Sterne mit einer Gesamtmasse von 700 . Der Radius beträgt 3.7 pc, die Sterndichte im Zentrum 50 Sterne pc–3, und die mittlere Sterngeschwindigkeit 0.89 km s–1. Auf den länger belichteten Aufnahmen taucht im Abstand von 12.3 in Richtung SSE ein unbekannter offener Sternhaufen auf, der einen Radius von etwa 4.3 hat und etwa 150 Sterne bis zur GrenzgrößeV19m enthält.
Mitteilungen Serie A. 相似文献
The open cluster NGC 5617 was investigated by the strip method on charts of photographs with different exposure times taken with the 1-m Schmidt telescope of the European Southern Observatory. The cluster contains about 460 stars with a total mass of 700 . Its radius amounts to 3.7 pc; the star density in the center is 50 stars pc–3; and the mean stellar velocity, 0.89 km s–1. On longerexposed photographs at a distance of 12.3 in direction to SSE an unknown open star cluster becomes visible with a radius of 4.3, containing about 150 stars to the limiting magnitudeV19m.
Mitteilungen Serie A. 相似文献
5.
It is shown on the basis of analyzing the LASCO/SOHO data that the main quasi-stationary solar wind (SW), with a typical lifetime of up to 10 days, flows in the rays of the streamer belt. Depending on R, its velocity increases gradually from V3 km s–1 at R1.3 R
to V170 km s–1 at R15 R
. We have detected and investigated the movement of the leading edge of the main solar wind at the stage when it occupied the ray, i.e., at the formative stage of a quasi-stationary plasma flow in the ray. It is shown that the width of the leading edge of the main SW increases almost linearly with its distance from the Sun. It is further shown that the initial velocity of the inhomogeneities (`blobs') that travel in the streamer belt rays increases with the distance from the Sun at which they originate, and is approximately equal to the velocity of the main solar wind which carries them away. The characteristic width of the leading edge of the `blob' R
, and remains almost unchanging as it moves away from the Sun. Estimates indicate that the main SW in the brightest rays of the streamer belt to within distances at least of order R3 R
represents a flow of collisional magnetized plasma along a radial magnetic field. 相似文献
6.
A model of 3He enrichments, which was proposed recently, is extended to study enhancements of heavy ions in high-energy particles. With weak currents parallel to the ambient magnetic field, oblique ion-acoustic waves and H cyclotron waves can become unstable. The former can have much greater growth rates at frequencies 3
He than at 4
He near the marginal states of instabilities. The latter can be unstable at 3
He for a wide region of plasma parameters. Thus they could cause 3He enrichments through cyclotron resonances. At the same time, these waves can resonate with first or higher harmonics of cyclotron frequencies of many other ions. We investigate these resonant ions for several cases of plasma temperature. This model predicts enhancements of heavy elements and of neutron-rich isotopes at T 10 MK. It shows heavy ion enhancements also at T 4 MK. Clear differences between these two temperatures, however, can be seen in charge states of ions. At T 2 MK, light ions as well as heavy ions can have cyclotron resonances with these waves, which suggests that such low temperatures are excluded. 相似文献
7.
Based on analyzing corona images taken by the LASCO C1, C2, and C3 instruments, a study is made of the behavior of the streamer belt spanning one half of the 1996–2001 cycle of solar activity, from minimum to maximum activity, in the absence of coronal mass ejections. It is shown that: (1) The position of the streamer belt relative to the solar equator is generally characterized by two angles: o and E, where o is the latitudinal position (near the solar surface) of the middle of the base of the helmet, the top of which gradually transforms to a ray of the streamer belt with a further distance from the Sun, and E is the latitude of this ray for R>5–6 R
from the Sun's center where the ray becomes radial. (2) Only rays lying at some of the selected latitudes o retain their radial orientation (oE) throughout their extent. Namely: o0° (equator), o±90° (north and south poles), and the angle o lying in the range ±(65°–75°) in the N- and S-hemispheres. (3) A deviation of rays from their radial orientation in the direction normal to the surface of the streamer belt occurs: for latitudes o<|65°–75°| toward the equator (>0°) reaching a maximum in the N and S hemispheres, respectively, when OM40°, and OM–42° for latitudes o>|65°–75°| toward the pole (<0°). The regularities obtained here are a numerical test which can be used to assess of the validity of the theory for describing the behavior of the Sun's quasi-stationary corona over a cycle of solar activity. 相似文献
8.
Satoshi Hinata 《Astrophysics and Space Science》1978,55(2):427-439
We determine the momentum distribution of the relativistic particles near the Crab pulsar from the observed X- and -ray spectra (103109 eV), provided that the curvature radiation is responsible for it. The power law spectrum for the relativistic electrons,f()
–5, reproduces a close fit to the observed high-energy photon spectrum. The theoretically determined upper limit to the momentum (due to radiation damping),
M
8×106, corresponds to the upper cut-off energy of the -ray spectrum, 109 eV. The lower limit to the momentum,
m
1.8×105, is chosen such that flattening of the X-ray spectrum below 10 keV is simulated. The number density of these electrons is found to be much higher than the Goldreich-Julian density. We also discuss pulse shape and polarization of high-energy photons. The extremely high density of particles and the steep momentum spectrum are difficult to understand. This may imply that another, more efficient, mechanism is in operation. 相似文献
9.
It is shown that a cylindrical plasma column supporting a longitudinal fieldB
z
and an azimuthal fieldB
has a fastest-growing mode in whichkR
01 (k=wave number,R
0=radius of the column). If we assume that plasma is ejected from a galaxy to form a jet, filament or bridge of length 5 kpc,R
00.5 kpc, density 10–24 gm cm–3 with a dragged-out field of strengthB
z
10–5 Gauss (from a parent field 10–6 Gauss), such a column must eventually fragment by the action of a hydromagnetic instability, breaking up into a number 10 of regularly-spaced condensations. It is, therefore, predicted that features like the M87 jet should show incipient nucleation with 3–10 knots, and that periodically-spaced objects of the type noted by Arp may have resulted from the action of such an instability. 相似文献
10.
With the help of a model atmosphere of the Sun we evaluate the pole-equator difference in flux (as measured by Dicke and Goldenberg) assuming the following type of pole-equator temperature difference (T=T
e
–T
p
): (a) T 2K for > 0 (0 0.05); (b) T 10K for < 0.The small T at all optical depths given by (a) could, for example, be due to a pole-equator difference in effective temperatures. At small optical depths a difference in mechanical heating could give rise to the larger temperature difference given by (b). We compare the results of our calculations with Dicke and Goldenberg's observations.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
11.
Very Large Array (VLA) observations of compact transient sources on the Sun at 2 cm wavelength are presented. These sources have angular sizes of 5–25, brightness temperatures of T
B 1–3 × 105 K, and lifetimes ranging between a few minutes to several hours. The emission originates in regions of diffuse plage and quiet Sun, where the photospheric magnetic fields are relatively weak (H 100 G). In some cases the 2 cm radiation may be explained as the thermal bremsstrahlung of a dense (N
e 1010 cm-3) plasma in the transition region. For other sources, the relatively high circular polarization (
c 40–50 %) suggests a nonthermal emission mechanism, such as the gyrosynchrotron radiation of mildly relativistic electron with a power-law spectrum. 相似文献
12.
M. Dersarkissian 《Astrophysics and Space Science》1986,126(2):409-412
When cosmic quantum mechanics is applied to a double galaxy, the result is mass limits in order for the two galaxies to form a quantum binary system. For a non-relativistic theory (based on the Schrödinger wave equation), the mass limits are: (m
g)max 1012
M
and (m
g)min 1010
M
. One possible consequence appears to be a Newtonian gravitational constant that varies with cosmic time, with its value larger in the cosmic past. 相似文献
13.
J. E. Dyson 《Astrophysics and Space Science》1968,1(3):388-405
A model is constructed of a spherically symmetric self-gravitating condensation of neutral hydrogen immersed in anHii region. The structure of the condensation is represented by the isothermal gas sphere at a temperature of 100°K. Typical parameters of such a condensation compatible with the estimated ultra-violet radiation field in the central regions of the Orion Nebula are, mass 1M
; radius 1016 cm; mean density 10–15 gm cm–3. The condensations are not static configurations but evolve because of mass loss by ionization from their surfaces. Perhaps 5% become gravitationally unstable and collapse. The remainder act as sources of ionized gas which flows into the surrounding nebula. 相似文献
14.
K. T. Alfriend 《Celestial Mechanics and Dynamical Astronomy》1971,4(1):60-77
The stability ofL
4 and the motion aboutL
4 in the restricted problem of three bodies is investigated when there is three-to-one commensurability between the long and short periods of motion, that is, when the mass ratio has the value =0.013516.... The two time scale method is used (1) to show thatL
4 is an unstable equilibrium point when =3, (2) to determine for what initial conditions periodic orbits occur when 3, (3) to determine the stability of the periodic orbits, and (4) to investigate the boundedness of the motions aboutL
4 when 3. 相似文献
15.
It has been shown that Alfvén waves can drive non-inductive current in solar coronal loops via collisional or collisionless damping. Assuming that all the coronal-loop density of dissipated wave power (W= 10–3 erg cm–3 s–1), which is necessary to keep the plasma hot, is due to Alfvén wave electron heating, we have estimated the axial current density driven by Alfvén waves to be jz 103–105 statA cm–2. This current can indeed support the quasi-stationary equilibrium and stability of coronal loops and create the poloidal magnetic field up to B
1–5 G. 相似文献
16.
The emission spectra and their time variations of gyro-synchrotron emission from an ensemble of energetic electrons are computed for some initial power-law distributions of the electron energies N()d=
–
with =2 or 4. The spectra and decay curves of the emission are compared with solar microwave bursts in order to separately estimate the magnetic field H and . From a limited number of observations, we have 3 and H 103 gauss for the microwave impulsive bursts, and 2 and H (500–1000) gauss for the microwave type-IV bursts. 相似文献
17.
We have mapped two solar active regions using the VLA at three closely spaced frequencies (4496, 4716, and 4996 MHz) in an attempt to determine the origin of the steep spectra (index –5 to –8) sometimes observed with large single telescopes. One of the regions observed indeed shows an anomalously large slope ( –6) compared to the usual ( –2 to –2.5). The other region shows a similar slope ( –5) but with a larger range of statistical error. Two possible explanations for such steep edges in solar spectra are (1) transmission effects of neutral current sheets, and (2) the appearance of cyclotron lines. The internal evidence of the microwave maps and simultaneous optical observations favor an explanation in terms of cyclotron lines.On leave from Indian Institute of Astrophysics, Bangalore, India. 相似文献
18.
Using the flux-transport equation in the absence of sources, we study the relation between a highly peaked polar magnetic field and the poleward meridional flow that concentrates it. If the maximum flow speed
m greatly exceeds the effective diffusion speed /R, then the field has a quasi-equilibrium configuration in which the poleward convection of flux via meridional flow approximately balances the equatorward spreading via supergranular diffusion. In this case, the flow speed () and the magnetic field B() are related by the steady-state approximation () (/R)B()/B() over a wide range of colatitudes from the poles to midlatitudes. In particular, a general flow profile of the form sin
p
cos
q
which peaks near the equator (q p) will correspond to a cos
n
magnetic field at high latitudes only if p = 1 and
m = n /R. Recent measurements of n 8 and 600 km2 s–1 would then give
m 7 m s–1. 相似文献
19.
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
20.
A spectral analysis of the fluctuations of the infrared sky radiance at 10m was made at the ESO-site of La Silla in Northern Chile. The data are compared to literature. The consequences of the results on infrared observing for future large telescopes are discussed: our data suggest that in order to achieve background noise limited performance in the 10m atmospheric window chopping with frequencies of 8 Hz and amplitudes of 10 arcsec is mandatory.based on observations obtained at the European Southern Observatory, La Silla, Chile 相似文献