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1.
The distribution of polar faculae with respect to latitude is investigated, using data obtained at the Ussuriysk Observatory during the years 1963–1994. To correct the data for the effect of visibility, a visibility function of polar faculae is derived. Corrected surface density of polar faculae is calculated as a function of latitude and time. During most part of each solar cycle, polar faculae exhibit pronounced concentrations at high latitudes with maxima of the surface density located near the poles. Such concentrations of polar faculae (below referred to as `polar condensations') are formed after a lapse of 1–2 years from the polar magnetic field reversals, and then they persist for 7–9 years, until the high-latitude magnetic fields again start to reverse. During several years after the sunspot minima, the polar condensations co-exist with the new latitudinal belts of polar faculae which appear at middle latitudes and then migrate toward the poles. To describe the evolution of the polar condensations quantitatively, the polar faculae density n at latitudes above 60° has been approximated by means of the power law nn
0 cosm where is polar angle. The parameters n
0 and m both are found to vary during the course of the solar cycle, reaching maximum values near or shortly after the minimum of sunspot activity. At the minimum phase of the solar cycle, on average, the surface density of polar faculae varies as cos14. In addition to the 11-yr variation, the latitude–time distribution of polar faculae exhibits short-term variations occurring on the time scale of 2–3 years. 相似文献
2.
E. Wiehr 《Solar physics》1970,15(1):148-157
Measurements of the circular polarization V in different lines show that the deduced magnetic field strength and flux are systematically influenced by variations of the line absorption coefficient from photosphere to spot and faculae.Disbalances between preceding and following flux seem to be due mainly to such variations rather than to real physical conditions in active regions.The spatial distribution of the normal component of the magnetic field in an active region near the disc center have been observed during two days using the temperature insensitive line Fe 6302.5. The initial field structure seems to become more and more bipolar. The increase of the flux exceeds that of the area thus suggesting the appearance of new magnetic fields. Backward extrapolation in time leads to a date of first appearance of the magnetic field which agrees with the appearance of first H anomalies. 相似文献
3.
I ±V profiles of the Fei 5247 and 5250 lines in the 2B flare of June 16, 1989 have been analyzed. A bright knot of the flare outside the sunspot where the central intensity of H reached a peak value of 1.4 (relative to the continuum) has been explored. The Fei 5250/Fei 5247 magnetic line ratio based on the StokesV peak separations of these lines at five evolutionary phases of the flare (including the start of the flare, the flash phase, the peak and 16 min after the peak) has been analyzed. It was found that the StokesV peak separation for the Fei 5250 line was systematically larger than that of the Fei 5247 line. This is evidence for the presence in the flare of small-scale flux tubes with kG fields. The flux tube magnetic field strength was about 1.1 kG at the start of the flare and during the flash phase, 1.55 kG during the peak, and 1.38 kG 16 min after the peak. The filling factor,, appears to decrease monotonically during the flare. 相似文献
4.
We investigate a latitude–time distribution of polar faculae observed at Ussuriysk Observatory in years 1966–1986. The distribution is compared with the longitude-averaged (zonal) magnetic field of the Sun calculated from the data obtained at Mount Wilson Observatory in the years 1966–1976, and at Kitt Peak National Observatory during the period from 1976 to 1985. We found that slow, poleward-directed migration of the polar faculae zones occurring during the course of the solar cycle is not a continuous process, but it contains several episodes of appearance and fast poleward drift of new zones of polar faculae. At the rising phase of the solar cycle, new zones of polar faculae appear at latitudes as low as 40°, but the ones observed during the declining phase of the solar cycle originate at higher latitudes of 50–55°. Such episodes of appearance and fast migration of the polar faculae zones are associated with the poleward-directed streams of magnetic field originated at low latitudes. Moreover, we found some evidence for existence of an additional component of the polar faculae activity that reveals an equatorward migration during the course of the solar cycle. We also investigated a relationship between the number of polar faculae, n, and absolute magnetic flux z of the zonal mode of the solar magnetic field. We found that within the polar zones of the Sun, substantial correlation between temporal variations of n and z takes place both on the time scale of the solar cycle and on a shorter time scale of 2–4 years. The relationship between the number of polar faculae and magnetic flux may be approximated by a linear dependence n=0.12z (where z is expressed in 1021 Mx), except for time interval 1977 through 1980 for which the factor of proportionality is found to have a systematically larger value of 0.20. 相似文献
5.
We have compared the latitudinal distributions of polar faculae, green coronal emission maxima, prominences and of a new index of enhanced geomagnetic recurrence with the distribution of magnetic fields during the cycles Nos. 20 and 21.We did not find a distinct high-latitude initial stage of an extended cycle in the corona, prominences and polar faculae distribution. On the contrary, it seems that the polar faculae and their following polarity magnetic fields represent the last evolutionary phase of a magnetic activity cycle lasting 15–17 years. The enhanced recurrent geomagnetic activity seems to be related to the old cycle fields.All studied phenomena clearly display two types of latitudinal distribution: the polar belts, into which the old following polarity fields have been transported from the equatorial belt where both the polarities developin situ simultaneously, but in which the leading polarity fields only remain, crossing the equator during the minimum of activity, to play the same role on the opposite hemispheres in the new cycle.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
6.
Edward N. Frazier 《Solar physics》1971,21(1):42-53
Simultaneous observations of photospheric magnetic fields, Caii K emission, the photospheric network and continuum faculae show that these four quantities are correlated in a complicated manner. The photospheric and calcium networks show increasing contrast with increasing magnetic field strength up to field strengths of about 500 G. Higher values of the magnetic field are found only in pores and sunspots. Continuum faculae also show increasing contrast with increasing magnetic field strength (even at the disk center), but this contrast reaches a maximum at field strengths of about 200 G. At higher field strengths, continuum faculae become monotonically darker until pore or spunspot conditions are reached.Measurements of the photospheric network and the continuum faculae over a wide range of result in families of limb contrast curves. These curves indicate that the dependence on H is as important as the dependence on . They also indicate that the magnetic field has a preferred inclination of about 50°. The facular contrast shows little dependence on resolution. This is interpreted in terms of a geometric model in which faculae are clumps of many individual flux tubes. These tubes are closely packed and unresolvable in the photosphere, but are more widely spaced, and therefore resolvable, in the low chromosphere.Visiting Astronomer, Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
7.
Gary A. Chapman 《Solar physics》1970,14(2):315-327
Semi-empirical models of solar faculae, cospatial with strong photospheric magnetic fields, have been constructed from continuum observations. The center-to-limb contrast of the various models was computed taking into account their geometrical shape. The adopted model whose horizontal size was taken to be 750 km, indicates that, in field regions, the temperature begins to rise outwards at z -125 km (above 5000 = 1) and that the extrapolated temperature at z -400 km is about 1500 K above that of the undisturbed atmosphere; the electron density is higher by a factor of about 30. 相似文献
8.
This contribution deals with the properties of small-scale magnetic elements at the polar caps of the Sun. Spectro-polarimetric observations, obtained with high spatial resolution with the Gregory Coudé Telescope at the Observatorio del Teide on Tenerife, were analysed. We find, though with limited data sets, that polar faculae differ in two aspects from faculae of the network in non-active regions near the equator (equatorial faculae): (1) Polar faculae appear to have the same magnetic polarity as the general polar magnetic field. Presumably, the latter is rooted in the small-scale faculae. The equatorial faculae show both magnetic polarities. (2) Polar faculae, with a size of 3.5 ± 1.3, are larger than equatorial faculae with 2.1 ± 0.4. Yet as for equatorial faculae, polar faculae possess kilogauss magnetic fields. 相似文献
9.
B. Ruiz Cobo J. C. Del Toro Iniesta M. Collados J. Sánchez Almeida 《Astrophysics and Space Science》1990,170(1-2):113-116
The diagnostic method proposed by Landi Degl'Innocenti and Landolfi (1982), based on the observation of circular polarization, has been generalized to derive the thermodynamic properties of unresolved magnetic elements in the solar atmosphere. The final aim is to derive the height dependence of several parameters of the flux tube atmosphere (such as temperature, magnetic field and velocity distributions, macroturbulence and filling factor). We have used a perturbation method based on the concept of response functions for the Stokes profiles introduced by Landi Degl'Innocenti and Landi Degl'Innocenti (1977). We present here the preliminary results of invertingV-profiles by an iterative standard least-squares technique, which allows to find the magnetic 1-D atmosphere consistent with simulated data.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
10.
Preliminary results on new CCD photometry inV andB bands of approximately 5000 stars in four overlapping fields in the globular cluster M3 are presented. The colour-magnitude diagram shows a very well-defined sequence with a small scatter, going fainter than previously published work on this cluster. The turn-off point found atV=19.1±0.2 mag and (B-V)=0.445±0.01, is slightly redder than those obtained in previous studies.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
11.
The propagation of spiral density waves in a differentially rotating, self-gravitating, magnetoactive and highly flattened disk is investigated by using the asymptotic theory for tightly wound spirals developed by Lin and his collaborators. We adopt the continuum fluid model as the primary basis, and our treatment will be largely analytical. The disk plasma is studied in the frozen field approximation and inhomogenceous magnetic fields in the plane of the disk are considered in detail.In a differentially rotating disk with strong magnetic fields, the field lines will be considerably distorted and the mutual influence of magnetic fields and differential rotation is by no means obvious.In this paper we present a new asymptotic dispersion relation for tightly wound spiral density waves with magnetic fields along the spiral armsB
(r). The effects of the magnetic fields lead to such terms likek
2(a
2 +V
A
2
), wherek is the wave number,a represents the speed of sound,V
A = (B
2/4)1/2 is the Alfvén speed,B denotes the field strength, and is the plasma density. These terms depict the well-known magnetoacoustic waves and could have been anticipated without a detailed computation. However the interaction of magnetic fields and differential rotation may give rise to other significant terms which are not so easy to foresee.We also present a more exact local dispersion relation by using the WKB approximation and study the effects of magnetic fields on the growth rate through the parametersQ andJ defined in the literature.Although the effects of the magnetic fields are rather insignificant for applications to Galactic dynamics, the effects of the magnetic fields are important for applications to star formation and problems related to the solar nebula. 相似文献
12.
High-spatial-resolution spectra of limb faculae show spatial displacements of line cores relative to the adjacent continuum at cos<0.35, confirming results from earlier photographic analyses. The observed displacements are geometric measures which probe the upper atmospheric layers of fluxtubes forming facular grains. We selected spectra with highest contrast and smallest width of the facular continuum streaks, in order to avoid clustered structures. The spatial displacements of Stokes-Q and -V maxima were also measured: we find Q-signals spatially located near the continuum, as is expected from their origin in line wings; V-signals – which should give evidence for the existence of horizontal fields – are not found, except for one case of a 'hidden' pore. 相似文献
13.
J. J. Brants 《Solar physics》1985,98(2):197-217
Scatter plots of various pairs of spectral-line parameters that describe the magnetic field and the line-of-sight velocity are discussed in order to relate magnetic structures and the line-of-sight velocity field with characteristic areas of an emerging flux region (EFR).Strong magnetic fields, occurring over about 20% of the resolution elements in the EFR, are either slightly to moderately inclined or transverse. Slightly to moderately inclined strong fields occur in patches near the border of the EFR; the filling factors per resolution element are large, and field strengths are between 800 and 2000 G, and up to 2500 G in pores. There are only a few faculae in the EFR; most of these are located near rapidly growing pores of following polarity.The strongly inclined strong magnetic fields, with field strengths exceeding 1000 G, are located in slightly darkened resolution elements near the line B
= 0 separating the magnetic polarities, near large-scale and small-scale upflows. In the central region of the EFR there are some small elements with strongly inclined field of low average field strength of about 500 G, and a tendency for a small-scale upward velocity. These elements may correspond to tops of flux loops during emergence.In 80% of the resolution elements within the EFR the magnetic flux density (averaged over the resolution element) is low, less than 120 G.There is a persistent large-scale velocity field, with upflows near the line B
= 0 separating the magnetic polarities and with downflows near rapidly growing pores of following polarity. Some examples of strong small-scale upflows are found in the central region of the EFR, and strong small-scale downflows near rapidly growing following pores. Within the pores and faculae there are no significant small-scale line-of-sight velocities.Based on observations obtained at the Sacramento Peak Observatory (operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation). 相似文献
14.
U. Geppert 《Astrophysics and Space Science》1990,168(2):253-261
The influence of magnetic field and rotation on the occurrence of convective instabilities in the liquid layer of neutron star envelopes has been investigated. The critical wavelength
c
, which denotes the boundary between stable and unstable behaviour of convective disturbances, is calculated for a neutron star model as a function of magnetic field and rotation. It is shown that the strength of the magnetic fields of neutron stars strongly suppresses the onset of convection, whereas the limiting effect of rotation acts only if the magnetic field vanishes. 相似文献
15.
A. A. Pevtsov 《Solar physics》1992,141(1):65-73
Using observational data on 14 sunspots from the Sayan Observatory vector magnetograph, a study was made of the relationship between the sunspot magnetic field and the Evershed motions. It is shown that the central area of the solar disk is dominated by an anti-correlation of the longitudinal magnetic field B
and the line-of-sight velocity V
when a maximum of V
corresponds to the neutral line of the longitudinal field. Near the limb there usually is a coincidence of the field and velocity neutral lines. There is evidence for the possible asymmetric character of the effect with respect to the central meridian. 相似文献
16.
Martin Beech 《Astrophysics and Space Science》1989,152(2):329-335
The V variations of ellipsoidal variables are investigated as a function of the spectral type of the primary. A model is developed on the assumption that the primary has near Main-Sequence characteristics. It is argued that the observed minimum in the V variations around spectral type F is real and is due to variations in the gravity-darkening exponent . The absolute upper limit to V variations is found to be 0.2 mag. 相似文献
17.
A magnetopause that separates two regimes of different flow, additional to the separation of a magnetic field from a field-free plasma, gives rise to the formation of asymmetric Stokes profiles. Using a simple two-layer model atmosphere, where one layer comprises a magnetic field, the other being field-free, it is shown by analytical derivation that a wide variety of Stokes V profiles can be produced, having amplitude asymmetries a in the range –a. These include two-humped V profiles, which have two lobes of equal sign. For the most simple models, the asymmetry depends on the ratio of continuum intensity to the Planck radiation intensity of the magnetic layer at the wavelength of the spectral line under consideration, and on the line depth. Two-humped profiles (|a|>1) require the temperature of the magnetic layer to surpass the temperature of the line-core forming region, implying a temperature inversion, so that the V profile is partially in emission. The confrontation of this formation scenario with properties of observed one-lobe profiles of quiet-Sun network regions is inconclusive due to insufficient spatial resolution and lack of a sufficient sample of simultaneously recorded Stokes spectral lines of varying line depths. It seems, however, to be in good agreement with the observed frequent occurrence of abnormal V profiles of the very strong Nai D
2 and D
2 spectral line. A possible observational verification for the present formation scenario of abnormal Stokes V profiles and a novel method of Stokes inversion are discussed. 相似文献
18.
An exact analysis of the effects of mass transfer on the flow of a viscous incompressible fluid past an uniformly accelerated vertical porous and non-porous plate has been presented on taking into account the free convection currents. The results are discussed with the effects of the Grashof number Gr, the modified Grashof number Sc, the Schmidt number Sc, and the suction parametera for Pr (the Prandtl number)=0.71 representating air at 20°C.Nomenclature
a
suction parameter
-
C
species concentration
-
C
species concentration at the free stream
-
g
acceleration due gravity
- Gc
modified Grashof number (vg*(C
–C
)/U
0
3
)
- Pr
Prandtl number (C
p/K)
-
T
temperature of the fluid near the plate
-
T
dimensionless temperature near the plate ((T-T
)/(T
-T
))
-
U(t)
dimensionless velocity of the plate (U/U
0)
-
v
normal velocity component
-
v
0
suction/injection velocity
-
x, y
coordinate along and normal to the plate
-
v
kinematic viscosity (/gr)
-
C
p
specific heat at constant pressure
-
C
w
species concentration at the plate
-
C
non-dimensional species concentration ((C-C
)/(C
w
-C
))
- Gr
Grashof number (g(T
w
-T
)/U
0
3
)
-
D
chemical molecular diffusivity
- K
thermal conductivity
- Sc
Schmidt number (/D)
-
T
w
temperature of the plate
-
T
free stream temperature
-
t
time variable
-
t
dimensionless time (tU
0
2
/)
-
U
0
reference velocity
-
u
velocity of the fluid near the plate
-
u
non-dimensional velocity (u/U
0)
-
v
dimensionless velocity (v/U
0)
-
v
0
non-dimensionalv
0
(v
0
/U0)=–at–1/2
-
y
dimensionless ordinate (yU
0/)
-
density of the fluid
-
coefficient of viscosity 相似文献
19.
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
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
20.
J. O. Stenflo 《Solar physics》1988,114(1):1-19
A search for linear polarization due to the transverse Zeeman effect in quiet regions near the heliographic north pole has been carried out. The aim is to determine new constraints on the properties of the hidden or turbulent magnetic flux of the Sun. As more than 90% of the total flux seen in magnetograms has its source in kG fluxtubes with an average filling factor of less than 1%, the term hidden magnetic flux refers to the field in the remaining 99% of the photospheric volume, which remains undetected in ordinary magnetograms (at available levels of spatial resolution and sensitivity).Simultaneous recordings of the Stokes I, Q, and V profiles of the Fei 5250.22 and 5247.06 Å lines with 5 × 5 sec of arc spatial resolution have been made with the NSO McMath solar telescope. The analysis shows how the observed Stokes Q amplitudes, as well as the Q/V ratio in combination with the 5250/5247 Stokes V line ratio, provide constraints on the field strength and the angular distribution of the field vectors of the hidden magnetic flux. The field has to be tangled with opposite polarities mixed on a subarcsec scale, and the field vectors have to have large inclinations with respect to the vertical direction, with an angular distribution not far from being isotropic in the photosphere. Constraints on the strength of this tangled or turbulent magnetic field have been obtained by previous methods, which are reconsidered in view of their dependence on the assumed angular distribution. An upper limit of 100 G comes from determinations of magnetic line broadening, a lower limit of 10 G from observed Hanle-effect depolarization.In our observations the linear polarization has been recorded with a precision of 10-4 with good spectral resolution. Further improvements are impeded by the lack of telescopes with large photon collecting areas and small instrumental polarization. 相似文献