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1.
N. N. Stepanian O. A. Andryeyeva Ya. I. Zyelyk 《Bulletin of the Crimean Astrophysical Observatory》2009,105(1):20-24
The time and latitude change of the flux and rotation of magnetic-field imbalance structures with various strengths has been determined from observations at the Kitt-Peak observatory for 26 years. The regularities revealed during the work allow this change to be explained as follows. The structure of the imbalance of the magnetic field of a particular strength emerges at the photosphere surface while possessing a rotation typical for the area of this structure formation. After this, the structure begins to drift along the meridian (toward the pole or toward the equator) while rotating at the same velocity and occupying several interval of latitudes. Having displaced to the poles from the emerging latitude by about 20° (or more, depending on the rotation period), structures that have a certain significant period cease to exist as a whole, giving rise to other structures with other significant rotation periods. From here it follows that the differential rotation of the layers responsible for forming the imbalance structures of fields with various strengths can be determined from the dependence of the rotation period on the latitude of the emergence of the imbalance structure. 相似文献
2.
The rotation of large-scale solar magnetic fields has been investigated by analysing a 20-yr series of synoptic maps of the radial magnetic field. For this purpose, a specially adapted method of spectral analysis was used. We calculated rotation spectra of the magnetic field as functions of the rotation period, heliographic latitude, and longitudinal wave number, k. These spectra reveal the existence of a number of discrete, rigidly rotating components (modes) of the magnetic field, whose rotation periods lie in the wide range from 26.5 to 30.5 days. The significant spectral maxima lie in the (rotation period–latitude) plane close to the curve that represents the differential rotation of small-scale magnetic features. For the first harmonic of the magnetic field (k=1) the properties of the rotation spectra are consistent with those reported by Antonucci, Hoeksema, and Scherrer (1990). However, the distribution of the rigidly rotating modes over rotation period and their latitudinal structure change systematically with the harmonic number k. As k increases, the mean distance P in rotation period between the modes decreases, from 1.2 days for k=1 to 0.3–0.5 days for k=4. This decreasing period separation is accompanied by a decrease of the characteristic latitude separation between the mode maxima. The latitudinal and longitudinal discrete spatial scales of the non-axisymmetric magnetic field appear to be connected with each other, as well as with the temporal scale P. 相似文献
3.
The observed phase relations between the weak background solar magnetic (poloidal) field and strong magnetic field associated
with sunspots (toroidal field) measured at different latitudes are presented. For measurements of the solar magnetic field
(SMF) the low-resolution images obtained from Wilcox Solar Observatory are used and the sunspot magnetic field was taken from
the Solar Feature Catalogues utilizing the SOHO/MDI full-disk magnetograms. The quasi-3D latitudinal distributions of sunspot
areas and magnetic fields obtained for 30 latitudinal bands (15 in the northern hemisphere and 15 in the southern hemisphere)
within fixed longitudinal strips are correlated with those of the background SMF. The sunspot areas in all latitudinal zones
(averaged with a sliding one-year filter) reveal a strong positive correlation with the absolute SMF in the same zone appearing
first with a zero time lag and repeating with a two- to three-year lag through the whole period of observations. The residuals
of the sunspot areas averaged over one year and those over four years are also shown to have a well defined periodic structure
visible in every two – three years close to one-quarter cycle with the maxima occurring at − 40° and + 40° and drifts during
this period either toward the equator or the poles depending on the latitude of sunspot occurrence. This phase relation between
poloidal and toroidal field throughout the whole cycle is discussed in association with both the symmetric and asymmetric
components of the background SMF and relevant predictions by the solar dynamo models. 相似文献
4.
V. A. Dogiel 《Solar physics》1983,82(1-2):427-436
A model of velocity field oscillations in the solar convective zone is suggested. The system of convective equations is investigated for a thin rotating spherical envelope when the rotation velocity is depended on the coordinates. It is shown that two different structures of convective cells (longitudinal, or latitudinal) can exist in the envelope depending on gradients values of the rotation velocity and Prandtl number. It is supposed that two different regimes of convection (stationary and autofluctuating) are possible in the envelope when the angular velocity gradients are determined by the convection itself. In the case of autofluctuating regime the alternation of longitudinal and latitudinal structure of convection is realized. If one assumes that on the Sun there exists an autooscillating convection regime, then the periods of the existence of latitudinal convection structure may be associated with long periods of activity minima since according to Cowling's theorem, the action of the axisymmetric magnetic field generation mechanism is impossible under conditions of axisymmetric velocity structures. 相似文献
5.
The Weber-Davis model of the solar wind is generalized to include the effects of latitude. The principal assumptions of perfect electrical conductivity, rotational symmetry, a polytropic relation between pressure and density, and a flow aligned magnetic field in a system rotating with the Sun, are retained. A flow aligned magnetic field in the rotating system may be expressed in terms of the flow velocity and density. Rotational symmetry fixes the longitudinal flow velocity Vφ in terms of the flow in the r?θ plane. Thus, the original three dimensional magnetohydrodynamic flow problem is reduced to a two dimensional hydrodynamic flow problem in the r?θ plane.There are three critical surfaces associated with the equations which supply conditions to determine three of six required boundary conditions. The specified boundary conditions at the base of the corona are the temperature, density, and magnitude of the magnetic field. The equations are then expanded about the radial, nonrotating Parker solution and an analytic solution is obtained for the resulting first order equations. The results show that for constant coronal boundary conditions there is a latitudinal flow toward the solar poles, as a result of magnetic stresses, which persists out to large distances for the Sun. Associated with this flow is a latitudinal component of the magnetic field. The radial flow parameters are, to within small first order differences, in agreement with those of the Parker and the Weber-Davis models of the solar wind.The equations are further generalized to permit first order latitudinal variations in the specified coronal boundary conditions. Results at 1 a.u. are presented for 5 per cent latitudinal differences between the equatorial and polar values. These results show that the solution at 1 a.u. is most sensitive to a latitudinal dependence in the boundary temperature and least sensitive to a latitudinal dependence in the magnetic field magnitude.A solution is then obtained for an approximate dipolar variation in the coronal magnetic field magnitude. This solution predicts that the latitudinal flow is initially toward the Equator due to magnetic channeling; however, this effect is rapidly overcome and the latitudinal flow at 1 a.u. is toward the pole and not significantly different from the solution for constant boundary conditions. 相似文献
6.
We have used the Hubble Space Telescope archived images of Jupiter for the period 1994-2000, complemented by ground-based telescopic observations, to study in detail the long-term properties of synoptic-scale anticyclonic vortices (size > 1500 km, lifetime > months). We have also analyzed a set of Voyager 1 and 2 images obtained in 1979 to compare anticyclone properties from the two different periods. The latitudinal range covered by this survey spans 75°N to 75°S, encompassing 12 anticyclonic zones. We present data on vortex size, aspect ratio, number, latitude location, lifetime, motion, interaction, and morphology for more than 100 vortices. We study empirically the relation between these properties and the mean ambient zonal flow.We show that most of these properties are not related to latitude and location relative to the jet pattern. However, a significant linear anticorrelation is found when plotting vortex relative speed (vortex propagation speed minus zonal flow velocity) against the zonal flow velocity at the central latitude of each vortex. As the mean eastward flow increases its velocity within a given anticyclonic domain, vortex velocity becomes more westward. This relation holds for all anticyclones except those moving at high velocities (at latitudes 20°S and 23°N), whose origin appears to be of a different nature. Moreover, there is also some evidence that the drift rate could be connected to the planetary minus flow vorticity gradient (most conspicuous at 40 and 45°N). We present simple dynamical interpretations of these observations. 相似文献
7.
K. Marubashi 《Planetary and Space Science》1979,27(5):603-615
Dynamic behavior of the coupled ionosphere-protonosphere system in the magnetospheric convection electric field has been theoretically studied for two plasmasphere models. In the first model, it is assumed that the whole plasmasphere is in equilibrium with the underlying ionosphere in a diurnal average sense. The result for this model shows that the plasma flow between the ionosphere and the protonosphere is strongly affected by the convection electric field as a result of changes in the volume of magnetic flux tubes associated with the convective cross-L motion. Since the convection electric field is assumed to be directed from dawn to dusk, magnetic flux tubes expand on the dusk side and contract on the dawn side when rotating around the earth. The expansion of magnetic flux tubes on the dusk side causes the enhancement of the upward H+ flow, whereas the contraction on the dawn side causes the enhancement of the downward H+ flow. Consequently, the H+ density decreases on the dusk side and increases on the dawn side. It is also found that significant latitudinal variations in the ionospheric structures result from the L-dependency of these effects. In particular, the H+ density at 1000 km level becomes very low in the region of the plasmasphere bulge on the dusk side. In the second model, it is assumed that the outer portion of the plasmasphere is in the recovery state after depletions during geomagnetically disturbed periods. The result for this model shows that the upward H+ flux increases with latitude and consequently the H+ density decreases with latitude in the region of the outer plasmasphere. In summary, the present theoretical study provides a basis for comparison between the equatorial plasmapause and the trough features in the topside ionosphere. 相似文献
8.
Coronal mass ejections (CMEs) are considered to be associated with large-scale, closed magnetic field structures in the corona. These structures change throughout the solar activity cycle following the evolution of the general solar magnetic field. To study the variation of CME characteristics with the evolution of coronal magnetic structures, we compute the 3-D coronal magnetic field at minimum and maximum of activity with a source-surface potential field model. In particular, we study the central latitude distribution of CMEs and the frequency of occurrence of the different CME types in these two periods. We find that most CMEs are indeed associated with large-scale, magnetically closed structures, and their latitudinal distribution follows the solar cycle latitudinal changes of the location of these structures. We also find that different CME types, which constitute different fractions of the total during the maximum and the minimum, are associated with different shapes and orientations of the closed structures at different times of the solar cycle. 相似文献
9.
O. A. Andryeyeva Ya. I. Zyelyk N. N. Stepanian Yu. T. Tsap 《Bulletin of the Crimean Astrophysical Observatory》2010,106(1):8-13
The cyclicity in the latitudinal distribution of the growth and decay rates of the total magnetic fluxes for weak magnetic
fields is investigated. The synoptic maps of the line-of-sight solar magnetic field strength obtained at the Kitt Peak Observatory
(USA) from January 1, 1977, to September 30, 2003, are used as the observational material. The latitudinal distributions of
the growth rates of total magnetic fluxes with various strengths constructed from them and their evolution during three solar
cycles have been compared with the analogous distribution of the total powers of rotation with various periods as well as
the relative sunspot numbers and areas. The results obtained allow a unified picture of the development of solar cycles for
weak and strong magnetic fields to be formulated. A new cycle begins with the growth of weak magnetic fields with a strength
of 0–200 G at latitudes 20°–25° in both hemispheres. This occurs one year before the activity minimum determined from sunspots.
Two years later, the growth rate of the total magnetic flux, which begins to propagate equatorward and poleward, reaches a
maximum. This process coincides with the onset of the growth of strong sunspot magnetic fields at the corresponding latitudes
and the formation of zones with a stable rotation. Subsequently, a fall-off in growth rate and then a flux decay for weak
magnetic fields correspond to the growth of the sunspot areas. In light of the dynamo theory, the results obtained suggest
that strong and weak magnetic fields are generated near the bottom of the convection zone, while the observed differences
in their behavior are determined by the interaction of emerging magnetic flux tubes of various strengths with turbulent plasma
motions inside the Sun. 相似文献
10.
S. Latushko 《Solar physics》1996,163(2):241-247
An analysis is made of mean latitudinal profiles of the meridional drift of the large-scale solar magnetic fields. The previously detected equatorward migration of the drift pattern in the course of a cycle is confirmed. Evidence for the existence of a near-equatorial narrow zone ±7° with an equatorward drift with a rate of about 1 m s-1 is obtained. The study revealed a significant difference in shapes and variations of average drift profiles for the large-scale magnetic field and small magnetic features (Komm, Howard, and Harvey, 1993). 相似文献
11.
Ilya Yu Alekseev 《Solar physics》2004,224(1-2):187-194
We present the first results of searching for stellar cycles by analysis of stellar spottedness using an algorithm developed
at the Crimean Astrophysical Observatory. For more than 35 red spotted stars, we find ten targets which demonstrate cyclic
variations of average latitudes and total areas of starspots. Activity cycles detected by this method have a typical cycle
length about 4–15 years which are analogous to the 11-year solar Schwabe cycle. Most of the program stars demonstrate a rough
analogue with the solar butterfly diagram. They show a tendency for the average starspot latitude lowering when the total
spot area grows. At the same time these stars show variations of stellar photometric period (which is traced by starspots)
with the starspot latitudinal drift analogously to the solar differential rotation effect. We suspect that the starspot latitudinal
drift rate and the differential rotation gradient depend on the stellar spectral type. 相似文献
12.
Both Uranus and Neptune are thought to have strong zonal winds with velocities of several 100 m s−1. These wind velocities, however, assume solid-body rotation periods based on Voyager 2 measurements of periodic variations in the planets’ radio signals and of fits to the planets’ magnetic fields; 17.24 h and 16.11 h for Uranus and Neptune, respectively. The realization that the radio period of Saturn does not represent the planet’s deep interior rotation and the complexity of the magnetic fields of Uranus and Neptune raise the possibility that the Voyager 2 radio and magnetic periods might not represent the deep interior rotation periods of the ice giants. Moreover, if there is deep differential rotation within Uranus and Neptune no single solid-body rotation period could characterize the bulk rotation of the planets. We use wind and shape data to investigate the rotation of Uranus and Neptune. The shapes (flattening) of the ice giants are not measured, but only inferred from atmospheric wind speeds and radio occultation measurements at a single latitude. The inferred oblateness values of Uranus and Neptune do not correspond to bodies rotating with the Voyager rotation periods. Minimization of wind velocities or dynamic heights of the 1 bar isosurfaces, constrained by the single occultation radii and gravitational coefficients of the planets, leads to solid-body rotation periods of ∼16.58 h for Uranus and ∼17.46 h for Neptune. Uranus might be rotating faster and Neptune slower than Voyager rotation speeds. We derive shapes for the planets based on these rotation rates. Wind velocities with respect to these rotation periods are essentially identical on Uranus and Neptune and wind speeds are slower than previously thought. Alternatively, if we interpret wind measurements in terms of differential rotation on cylinders there are essentially no residual atmospheric winds. 相似文献
13.
V. A. Perebeinos N. N. Stepanian V. G. Fainshtein G. V. Rudenko 《Bulletin of the Crimean Astrophysical Observatory》2011,107(1):43-50
Height variation of the magnetic field structure over groups of sunspots for heights ranging from the photosphere to the source
surface (R = 2.5 Ro, where Ro is the radius of the Sun) is examined. For all heights, starting from the photospheric level, groups of
sunspot are shown as being independent of long-lived boundaries of large-scale structures rotating with a period shorter than
the Carrington period. At heights of 1–1.5 Ro, there is a clear relation between sunspot groups and boundaries separating
the head and tail sunspots in the groups (the Hale boundaries). The rotation periods of these structures are close to the
Carrington period, their lifespan being less than three to five rotations. The maximal intensity of the solar magnetic field
drops by two orders when height increases from H = 1 to H = 1.1 Ro. Further decrease in intensity proceeds gradually (dropping by one order from H = 1.1 to 2.5 Ro). The results obtained can be considered as evidence that large-scale magnetic field structures and long-lived
boundries between them (the lines dividing polarities of the magnetic field or zero lines) all exist irrespective of sunspot
fields being generated by other sources than sunspots. At the photospheric level, active regions fields are superimposed on
these structures. 相似文献
14.
J. H. Piddington 《Astrophysics and Space Science》1977,47(1):237-252
Solar meridional drift motions are vitally important in connection with the origin of magnetic fields, the source of differential rotation, and perhaps convection. A large body of observational evidence is collated with the following conclusions. (i) Sunspot motions reveal latitudinal drifts (Figures 2 and 3) of a few metres per second which vary with latitude and have a strong 11-yr periodicity. There may also be a 22-yr component polewards during even cycles and equatorwards during odd. (ii) Various other tracers, all basically magnetic structures, show the 11-yr drifts at mid- and high latitudes up to the polar caps, motion being polewards during the three years starting just before minimum activity (Figure 4). (iii) The earlier evidence for giant cells or Rossby-type waves is shown to be merely misinterpretation of the hydromagnetic motions of tracers. Evidence against such giant eddies is found in the great stability of other tracer structures. (iv) From the various tracer motions a four cell axisymmetric meridional drift system is determined (Figure 5 (b)) with an 11-yr period of oscillation and amplitude a few metres per second. (v) These meridional oscillations must be a basic component of the activity cycle. They add to the difficulties of the dynamo theory, but may explain the emergence of stitches of flux ropes to form relatively small bipolar magnetic regions. (vi) The two cells also throw light on thetwo sunspot zones in each hemisphere, discussed earlier by Becker and by Antalová and Gnevyshev. 相似文献
15.
The Carte Synoptique catalogue of solar filaments from 1919 March to 1957 July, corresponding to complete cycles 16‐18, is utilized to show the latitudinal migrations of solar filaments at low (≤50°) and high (>50°) latitudes and the latitudinal distributions of solar filaments for all solar filaments, solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° and solar filaments whose maximum lengths during solar disk passage are larger than 70°. The results show the following. (1) The latitudinal migrations of all low‐latitude solar filaments and low‐latitude solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° follow the Spörer sunspot law. However, the latitudinal migration of low‐latitude solar filaments whose maximum lengths during solar disk passage are larger than 70° do not follow the Spörer sunspot law: there is no equatorward and no poleward drift. The latitudinal migration of high‐latitude solar filaments whose maximum lengths during solar disk passage are larger than 70° is more significant than those of all high‐latitude solar filaments and high‐latitude solar filaments whose maximum lengths during solar disk passage are less than or equal to 70°: there is a poleward migration from the latitude of about 50° to 70° and an equatorward migration from the latitude of about 70° to 50° of all high‐latitude solar filaments and high‐latitude solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° and there is a poleward migration from the latitude of about 50° to 80° and an equatorward migration from the latitude of about 80° to 50° of high‐latitude solar filaments whose maximum lengths during solar disk passage are larger than 70°. (2) The statistical characteristics of latitudinal distribution of solar filaments whose maximum lengths during solar disk passage are larger than 70° is different from those of all solar filaments and solar filaments whose maximum lengths during solar disk passage are less than or equal to 70° (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
The latitudinal migration of sunspots toward the equator,which implies there is propagation of the toroidal magnetic flux wave at the base of the solar convection zone,is one of the crucial observational bases for the solar dynamo to generate a magnetic field by shearing of the pre-existing poloidal magnetic field through differential rotation.The Extended time series of Solar Activity Indices(ESAI)elongated the Greenwich observation record of sunspots by several decades in the past.In this study,ESAI's yearly mean latitude of sunspots in the northern and southern hemispheres during the years 1854 to 1985 is utilized to statistically test whether hemispherical latitudinal migration of sunspots in a solar cycle is linear or nonlinear.It is found that a quadratic function is statistically significantly better at describing hemispherical latitudinal migration of sunspots in a solar cycle than a linear function.In addition,the latitude migration velocity of sunspots in a solar cycle decreases as the cycle progresses,providing a particular constraint for solar dynamo models.Indeed,the butterfly wing pattern with a faster latitudinal migration rate should present stronger solar activity with a shorter cycle period,and it is located at higher latitudinal position,giving evidence to support the Babcock-Leighton dynamo mechanism. 相似文献
17.
The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the ‘pile-up’ method and the F-test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle. 相似文献
18.
V. Holzwarth D. H. Mackay M. Jardine 《Monthly notices of the Royal Astronomical Society》2006,369(4):1703-1718
Observations of rapidly rotating solar-like stars show a significant mixture of opposite-polarity magnetic fields within their polar regions. To explain these observations, models describing the surface transport of magnetic flux demand the presence of fast meridional flows. Here, we link subsurface and surface magnetic flux transport simulations to investigate (i) the impact of meridional circulations with peak velocities of ≤125 m s−1 on the latitudinal eruption pattern of magnetic flux tubes and (ii) the influence of the resulting butterfly diagrams on polar magnetic field properties. Prior to their eruption, magnetic flux tubes with low field strengths and initial cross-sections below ∼300 km experience an enhanced poleward deflection through meridional flows (assumed to be polewards at the top of the convection zone and equatorwards at the bottom). In particular, flux tubes which originate between low and intermediate latitudes within the convective overshoot region are strongly affected. This latitude-dependent poleward deflection of erupting magnetic flux renders the wings of stellar butterfly diagrams distinctively convex. The subsequent evolution of the surface magnetic field shows that the increased number of newly emerging bipoles at higher latitudes promotes the intermingling of opposite polarities of polar magnetic fields. The associated magnetic flux densities are about 20 per cent higher than in the case disregarding the pre-eruptive deflection, which eases the necessity for fast meridional flows predicted by previous investigations. In order to reproduce the observed polar field properties, the rate of the meridional circulation has to be of the order of 100 m s−1 , and the latitudinal range from which magnetic flux tubes originate at the base of the convective zone (≲50°) must be larger than in the solar case (≲35°). 相似文献
19.
We examine the effects of rotation about a vertical axis on thermal convection with a simple model in which an inviscid, incompressible fluid of zero thermal conductivity and electrical resistivity is contained in a thin annulus of rectangular cross-section. The initial steady state assumed is one of no motion relative to the rotating frame with constant (unstable) vertical temperature gradient and uniform toroidal magnetic field. Small periodic disturbances are then introduced and the linearized perturbation equations solved. We also determine the second-order mean circulations and magnetic fields that are forced by non-zero Reynolds and thermal stresses and magnetic field transports.The solutions have several properties which are relevant to large-scale solar phenomena if giant long-lived convection cells exist on the sun. In particular, the convective cells are tilted in latitude in the same sense as bipolar magnetic regions, and induce vertical magnetic fields with the same tilt. They transport momentum across latitude circles through Reynolds stresses and induced meridional circulations thus setting up a differential rotation. Cells which grow slowly compared to the rotation rate and have comparable dimensions in latitude and longitude transport momentum toward the equator. The cells also form a poloidal magnetic field from initial toroidal field, in a manner similar to that put forth by Parker.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
20.
N. N. Stepanian O. A. Andryeyeva Ya. I. Zyelyk 《Bulletin of the Crimean Astrophysical Observatory》2009,105(1):1-9
Differences of magnetic field flows of “+” and “?” polarities, i.e. the imbalance of magnetic fields for 26 years—from January 1, 1977, to September 30, 2003—are investigated,. The synoptic maps of the longitudinal vector of Sun’s magnetic field strength obtained at the Kitt Peak National Observatory (United States) and kindly given to us by Dr. J. Harvey have served as the initial material. The imbalance of magnetic fields’ cyclicity features and the deviations from the dipole structure of Sun’s magnetic field are determined. The contribution of latitude zones and fields of various strength into the general magnetic flux from the Sun is found. The latter characteristic was compared with the Sun’s mean magnetic field (MMF) obtained from the observations of the Sun as a star (Kotov et al., 2002; Kotov, 2008). The obtained results testify that the imbalance is one of physical characteristics of the Sun. The confirmations of this conclusion are the strict regularities of the Sun’s dipole structure changing; the complicated character of the imbalance cyclicity, i.e., the multiplicity of cycles; the solar nature of MMF changing; and the distinction between two classes of magnetic fields in the imbalance characteristics. 相似文献