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1.
R. H. Dicke 《Solar physics》1988,115(1):171-181
It has previously been shown that the statistics of the phase fluctuation of the sunspot cycle are compatible with the assumption that the solar magnetic field is generated deep in the Sun by a frequency stable oscillator and that the observed substantial phase fluctuation in the sunspot cycle is due to variation in the time required for the magnetic field to move to the solar surface (Dicke, 1978, 1979). It was shown that the observed phase shifts are strongly correlated with the amplitude of the solar cycle. It is shown here that of two empirical models for the transport of magnetic flux to the surface, the best fit to the data is obtained with a model for which the magnetic flux is carried to the surface by convection with the convection velocity proportional to a function of the solar cycle amplitude. The best fit of this model to the data is obtained for a 12-yr transit time. The period obtained for the solar cycle is T = 22.219 ± 0.032 yr. It is shown that the great solar anomaly of 1760–1800 is most likely real and not due to poor data. 相似文献
2.
We present the data concerning the distribution of various sunspot magnetic classes over the solar butterfly diagram and discuss how this data can inform solar dynamo models. We use the statistics of sunspots that violate the Hale polarity law to estimate the ratio of the fluctuating and mean components of the toroidal magnetic field inside the solar convective zone. An analysis of the spatial distribution of bipolar, unipolar and complex sunspot groups in the context of simple dynamo models results in the conclusion that the mean toroidal field is relatively simple and maintains its shape during the course of the solar cycle (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
The relation of the solar cycle period and its amplitude is a complex problem as there is no direct correlation between these two quantities. Nevertheless, the period of the cycle is of important influence to the Earth's climate, which has been noted by many authors. The present authors make an attempt to analyse the solar indices data taking into account recent developments of the asymptotic theory of the solar dynamo. The use of the WKB method enables us to estimate the amplitude and the period of the cycle versus dynamo wave parameters in the framework of the nonlinear development of the one-dimensional Parker migratory dynamo. These estimates link the period T and the amplitude a with dynamo number D and thickness of the generation layer of the solar convective zone h. As previous authors, we have not revealed any considerable correlation between the above quantities calculated in the usual way. However, we have found some similar dependences with good confidence using running cycle periods. We have noticed statistically significant dependences between the Wolf numbers and the running period of the magnetic cycle, as well as between maximum sunspot number and duration of the phase of growth of each sunspot cycle. The latter one supports asymptotic estimates of the nonlinear dynamo wave suggested earlier. These dependences may be useful for understanding the mechanism of the solar dynamo wave and prediction of the average maximum amplitude of solar cycles. Besides that, we have noted that the maximum amplitude of the cycle and the temporal derivative of the monthly Wolf numbers at the very beginning of the phase of growth of the cycle have high correlation coefficient of order 0.95. The link between Wolf number data and their derivative taken with a time shift enabled us to predict the dynamics of the sunspot activity. For the current cycle 23 this yields Wolf numbers of order 107±7. 相似文献
4.
R. N. Bracewell 《Solar physics》1988,116(1):179-194
The Elatina formation in South Australia, which provides a rich fossil record of presumptive solar activity in the late Precambrian, is of great potential significance for the physics of the Sun because it contains laminae grouped in cycles of about 12, an appearance suggestive of the solar cycle. The actual spectrum of the lamina-thickness series is rather complex, 20 or more spectral lines having been recognized by Fourier analysis. It is shown how these numerous lines arise as combination frequencies, from a much simpler intrinsic spectrum, by rectification. Optical studies of the Sun have shown that there is a magnetic polarity reversal on the Sun every 11 years approximately, but terrestrial consequences of solar activity, for example in the ozonosphere or ionosphere, do not respond to solar magnetism; thus the negative-going semi-cycles of the full magnetic cycle are in effect rectified according to a linear law. Application of this knowledge to the Elatina formation shows that derectification simplifies the spectrum of the laminathickness series in exactly the way that one would expect if the solar cycle were at work here also. Zig-zag effect, an alternation of cycle thickness, is taken to be due, not to a beat phenomenon, but to rectification in the presence of a weak 345-year oscillation; subtraction of this oscillation after derectification is essential to the simplifying procedure. The fundamental period is established at a new sharper value of 23.7 ± 0.2 years as compared with the looser 22.2 ± 1.8 years for the modern sunspot series. This paper treats the laminae as varves laid down yearly and modulated in thickness in accordance with the late Precambrian sunspot activity for the year of deposition. Since the difference between 23.7 and 22.2 is less than a standard deviation it is premature to speculate that the sunspot cycle period has undergone secular change; indeed the possibility that the solar oscillator has been secularly stable is not ruled out. The high Q now demonstrated for the varve oscillator (around 120 compared with a previous value of 12) weakens support for that part of solar dynamo theory that ascribes the solar cycle to a self-sustaining relaxation osculation; conversely, the evidence for an internal solar clock mechanism is strenghtened. A wave propagation zone intervening between the clock and the solar surface could produce the intrinsic spectrum. 相似文献
5.
The Empirical Mode Decomposition (EMD) and Auto-Regressive model (AR) are applied to a long-term prediction of sunspot numbers. With the sample data of sunspot numbers from 1848 to 1992, the method is evaluated by examining the measured data of the solar cycle 23 with the prediction: different time scale components are obtained by the EMD method and multi-step predicted values are combined to reconstruct the sunspot number time series. The result is remarkably good in comparison to the predictions made by the solar dynamo and precursor approaches for cycle 23. Sunspot numbers of the coming solar cycle 24 are obtained with the data from 1848 to 2007, the maximum amplitude of the next solar cycle is predicted to be about 112 in 2011-2012. 相似文献
6.
The latitudinal location of the sunspot zones in each hemisphere is determined by calculating the centroid position of sunspot
areas for each solar rotation from May 1874 to June 2011. When these centroid positions are plotted and analyzed as functions
of time from each sunspot cycle maximum, there appear to be systematic differences in the positions and equatorward drift
rates as a function of sunspot cycle amplitude. If, instead, these centroid positions are plotted and analyzed as functions
of time from each sunspot cycle minimum, then most of the differences in the positions and equatorward drift rates disappear.
The differences that remain disappear entirely if curve fitting is used to determine the starting times (which vary by as
much as eight months from the times of minima). The sunspot zone latitudes and equatorward drift measured relative to this
starting time follow a standard path for all cycles with no dependence upon cycle strength or hemispheric dominance. Although
Cycle 23 was peculiar in its length and the strength of the polar fields it produced, it too shows no significant variation
from this standard. This standard law, and the lack of variation with sunspot cycle characteristics, is consistent with dynamo
wave mechanisms but not consistent with current flux transport dynamo models for the equatorward drift of the sunspot zones. 相似文献
7.
Long-term changes in the magnetic activity of the Sun were studied in terms of the empirical mode decomposition that revealed
their essential modes. The occurrence of grand minima was also studied in their relation to long-term changes in sunspot activity
throughout the past 11 000 yr. Characteristic timescales of long-term changes in solar activity manifest themselves in the
occurrence of grand minima. A quantitative criterion has been defined to identify epochs of grand minima. This criterion reveals
the important role of secular and bicentennial activity variations in the occurrence of grand minima and relates their amplitudes
with the current activity level, which is variable on a millennial timescale. We have revealed specific patterns in the magnetic
activity between successive grand minima which tend to recur approximately every 2300 yr but occasionally alternate with irregular
changes. Such intermittent activity behavior indicates low dimensional chaos in the solar dynamo due to the interplay of its
dominant modes. The analysis showed that in order to forecast activity level in forthcoming cycles, one should take into account
long-term changes in sunspot activity on a ≈2300-yr timescale. The regularities revealed suggest solar activity to decrease
in the foreseeable future. 相似文献
8.
Simple Model of a Stochastically Excited Solar Dynamo 总被引：2，自引：0，他引：2
The aim of this paper is to investigate the dynamical nature of the complexity observed in the time evolution of the sunspot
number. We report a detailed analysis of the sunspot number time series, and use the daily records to build the phase space
of the underlying dynamical system. The observed features of the phase space prompted us to describe the global behavior of
the solar cycle in terms of a noise-driven relaxation oscillator. We find the equations whose solutions best fit the observed
series, which adequately describe the shape of the peaks and the oscillations of the system. The system of equations obtained
from this fitting procedure is shown to be equivalent to a truncation of the dynamo equations. A linear transformation maps
the phase space of these equations into the phase space reconstructed from the observations. The irregularities of the solar
cycle were modeled through the introduction of a stochastic parameter in the equations to simulate the randomness arising
in the process of eruption of magnetic flow to the solar surface. The mean values and deviations obtained for the periods,
rise times and peak values, are in good agreement with the values obtained from the sunspot time series. 相似文献
9.
Robert M. Wilson 《Solar physics》1988,115(2):397-408
Correlated with the maximum amplitude (R
max) of the sunspot cycle are the sum (R
sum) and the mean (R
mean) of sunspot number over the duration of the cycle, having a correlation coefficient r equal to 0.925 and 0.960, respectively. Runs tests of R
max, R
sum, and R
mean for cycles 0–21 have probabilities of randomness P equal to 6.3, 1.2, and 9.2%, respectively, indicating a tendency for these solar-cycle related parameters to be nonrandomly distributed. The past record of these parameters can be described using a simple two-parameter secular fit, one parameter being an 8-cycle modulation (the so-called Gleissberg cycle or long period) and the other being a long-term general (linear) increase lasting tens of cycles. For each of the solar-cycle related parameters, the secular fit has an r equal to about 0.7–0.8, implying that about 50–60% of the variation in R
max, R
sum, and R
mean can be accounted for by the variation in the secular fit.Extrapolation of the two-parameter secular fit of R
max to cycle 22 suggests that the present cycle will have an R
max = 74.5 ± 49.0, where the error bar equals ± 2 standard errors; hence, the maximum amplitude for cycle 22 should be lower than about 125 when sunspot number is expressed as an annual average or it should be lower than about 130 when sunspot number is expressed as a smoothed (13-month running mean) average. The long-term general increase in sunspot number appears to have begun about the time of the Maunder minimum, implying that the 314-yr periodicity found in ancient varve data may not be a dominant feature of present sunspot cycles. 相似文献
10.
In this work we use an already-published method to infer a variation profile for the solar meridional circulation over the
last 250 years. We feed this variation profile into a numerical dynamo code, and we reconstruct a sunspot time series that
acts as a proxy for solar cycle activity. We perform three simulations with slightly different parameters, and the results
are compared with the observational data. The medium and large correlation coefficients between reconstructed and observational
time series seem to indicate that variations in meridional circulation play an important role in the modulation of solar activity. 相似文献
11.
“TOY” Dynamo to Describe the Long-Term Solar Activity Cycles 总被引：1，自引：0，他引：1
D. Volobuev 《Solar physics》2006,238(2):421-430
Secular variations of solar activity (Gleissberg and Suess cycles) have approximately 80 – 130 and 200 year periods. They
are manifested in both observed and proxy data. Here, we show that the basic dynamic features of the Schwabe cycle (asymmetry
of its growth and decay phases) and secular cycles (multi-frequency structure and irregular Grand-extremes), as well as a
connection between them, can be described by parameter tuning of the electromechanical “toy” dynamo system which has been
widely used to model the inversions of the geomagnetic field. An amplitude-frequency diagram for the model magnetic flux has
the same shape as the directly observed and reconstructed sunspot area indices.
An erratum to this article is available at . 相似文献
12.
A. A. Ruzmaikin 《Solar physics》1985,100(1-2):125-140
The basic features of the solar activity mechanism are explained in terms of the dynamo theory of mean magnetic fields. The field generation sources are the differential rotation and the mean helicity of turbulent motions in the convective zone. A nonlinear effect of the magnetic field upon the mean helicity results in stabilizing the amplitude of the 22-year oscillations and forming a basic limiting cycle. When two magnetic modes (with dipole and quadrupole symmetry) are excited nonlinear beats appear, which may be related to the secular cycle modulation.The torsional waves observed may be explained as a result of the magnetic field effect upon rotation. The magnetic field evokes also meriodional flows.Adctual variations of the solar activity are nonperiodic since there are recurrent random periods of low activity of the Maunder minimum type. A regime of such a magnetic hydrodynamic chaos may be revealed even in rather simple nonlinear solar dynamo models.The solar dynamo gives rise also to three-dimensional, non-axisymmetric magnetic fields which may be related to a sector structure of the solar field. 相似文献
13.
The purpose of the present study is to develop an empirical model based on precursors in the preceding solar cycle that can
be used to forecast the peak sunspot number and ascent time of the next solar cycle. Statistical parameters are derived for
each solar cycle using “Monthly” and “Monthly smoothed” (SSN) data of international sunspot number (R
i). Primarily the variability in monthly sunspot number during different phases of the solar cycle is considered along with
other statistical parameters that are computed using solar cycle characteristics, like ascent time, peak sunspot number and
the length of the solar cycle. Using these statistical parameters, two mathematical formulae are developed to compute the
quantities [Q
C]
n
and [L]
n
for each nth solar cycle. It is found that the peak sunspot number and ascent time of the n+1th solar cycle correlates well with the parameters [Q
C]
n
and [L]
n
/[S
Max]
n+1 and gives a correlation coefficient of 0.97 and 0.92, respectively. Empirical relations are obtained using least square fitting,
which relates [S
Max]
n+1 with [Q
C]
n
and [T
a]
n+1 with [L]
n
/[S
Max]
n+1. These relations predict a peak of 74±10 in monthly smoothed sunspot number and an ascent time of 4.9±0.4 years for Solar
Cycle 24, when November 2008 is considered as the start time for this cycle. Three different methods, which are commonly used
to define solar cycle characteristics are used and mathematical relations developed for forecasting peak sunspot number and
ascent time of the upcoming solar cycle, are examined separately. 相似文献
14.
Search for relationship between duration of the extended solar cycles and amplitude of sunspot cycle
A.G. Tlatov 《Astronomische Nachrichten》2007,328(10):1027-1029
Duration of the extended solar cycles is taken into the consideration. The beginning of cycles is counted from the moment of polarity reversal of large-scale magnetic field in high latitudes, occurring in the sunspot cycle n till the minimum of the cycle n + 2. The connection between cycle duration and its amplitude is established. Duration of the “latent” period of evolution of extended cycle between reversals and a minimum of the current sunspot cycle is entered. It is shown, that the latent period of cycles evolution is connected with the next sunspot cycle amplitude and can be used for the prognosis of a level and time of a sunspot maximum. The 24th activity cycle prognosis is made. The found dependences correspond to transport dynamo model of generation of solar cyclicity, it is possible with various speed of meridional circulation. Long-term behavior of extended cycle's lengths and connection with change of a climate of the Earth is considered. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
Guided by the recent observational result that the meridional circulation of the Sun becomes weaker at the time of the sunspot
maximum, we have included a parametric quenching of the meridional circulation in solar dynamo models such that the meridional
circulation becomes weaker when the magnetic field at the base of the convection zone is stronger. We find that a flux transport
solar dynamo tends to become unstable on including this quenching of meridional circulation if the diffusivity in the convection
zone is less than about 2×1011 cm2 s−1. The quenching of α, however, has a stabilizing effect and it is possible to stabilize a dynamo with low diffusivity with sufficiently strong
α-quenching. For dynamo models with high diffusivity, the quenching of meridional circulation does not produce a large effect
and the dynamo remains stable. We present a solar-like solution from a dynamo model with diffusivity 2.8×1012 cm2 s−1 in which the quenching of meridional circulation makes the meridional circulation vary periodically with solar cycle as observed
and does not have any other significant effect on the dynamo. 相似文献
16.
The paper presents the seasonal variation of 6300 Å line intensity at Calcutta with relative sunspot number, solar flare number and variable component of 10.7 cm solar flux. A study has been made and important results have been obtained which are as follows. (i) Intensity of 6300 Å line shows periodic variation with relative sunspot number, solar flare number and variable component of 10.7 cm solar flux during the period 1984–1986 which is the secondary peak of the descending phase of 21st solar cycle. (ii) 6300 Å line intensity at Cachoeira Paulista station, taken by Sahai et al. (1988), also shows periodic variation with solar parameters during the period 1978–1980 which is the peak phase of the solar cycle. (iii) A possible explanation of such a type of variation is also presented. 相似文献
17.
We present the results of a statistical study of the solar cycle based on the analysis of the superficial toroidal magnetic
field component phase space. The magnetic field component used to create the embedded phase space was constructed from monthly
sunspot number observations since 1750. The phase space was split into 32 sections (or time instants) and the average values
of the orbits on this phase space were calculated (giving the most probable cycle). In this phase space it is shown that the
magnetic field on the Sun’s surface evolves through a set of orbits that go around a mean orbit (i.e., the most probable magnetic cycle that we interpret as the equilibrium solution). It follows that the most probable cycle
is well represented by a van der Pol oscillator limit curve (equilibrium solution), as can be derived from mean-field dynamo
theory. This analysis also retrieves the empirical Gnevyshev – Ohl’s rule between the first and second parts of the solar
magnetic cycle. The sunspot number evolution corresponding to the most probable cycle (in phase space) is presented. 相似文献
18.
Solar cycle according to mean magnetic field data 总被引：1，自引：0，他引：1
V. N. Obridko D. D. Sokoloff K. M. Kuzanyan B. D. Shelting V. G. Zakharov 《Monthly notices of the Royal Astronomical Society》2006,365(3):827-832
To investigate the shape of the solar cycle, we have performed a wavelet analysis of the large–scale magnetic field data for 1960–2000 for several latitudinal belts and have isolated the following quasi-periodic components: ∼22, 7 and 2 yr. The main 22-yr oscillation dominates all latitudinal belts except the latitudes of ±30° from the equator. The butterfly diagram for the nominal 22-yr oscillation shows a standing dipole wave in the low-latitude domain (∣θ∣≤ 30°) and another wave in the sub-polar domain (∣θ∣≥ 35°) , which migrates slowly polewards. The phase shift between these waves is about π. The nominal 7-yr oscillation yields a butterfly diagram with two domains. In the low-latitude domain (∣θ∣≤ 35°) , the dipole wave propagates equatorwards and in the sub-polar region, polewards. The nominal 2-yr oscillation is much more chaotic than the other two modes; however the waves propagate polewards whenever they can be isolated.
We conclude that the shape of the solar cycle inferred from the large-scale magnetic field data differs significantly from that inferred from sunspot data. Obviously, the dynamo models for a solar cycle must be generalized to include large-scale magnetic field data. We believe that sunspot data give adequate information concerning the magnetic field configuration deep inside the convection zone (say, in overshoot later), while the large-scale magnetic field is strongly affected by meridional circulation in its upper layer. This interpretation suggests that the poloidal magnetic field is affected by the polewards meridional circulation, whose velocity is comparable with that of the dynamo wave in the overshoot layer. The 7- and 2-yr oscillations could be explained as a contribution of two sub-critical dynamo modes with the corresponding frequencies. 相似文献
We conclude that the shape of the solar cycle inferred from the large-scale magnetic field data differs significantly from that inferred from sunspot data. Obviously, the dynamo models for a solar cycle must be generalized to include large-scale magnetic field data. We believe that sunspot data give adequate information concerning the magnetic field configuration deep inside the convection zone (say, in overshoot later), while the large-scale magnetic field is strongly affected by meridional circulation in its upper layer. This interpretation suggests that the poloidal magnetic field is affected by the polewards meridional circulation, whose velocity is comparable with that of the dynamo wave in the overshoot layer. The 7- and 2-yr oscillations could be explained as a contribution of two sub-critical dynamo modes with the corresponding frequencies. 相似文献
19.
J. H. Piddington 《Solar physics》1972,22(1):3-19
The dynamo theory of the solar cycle as developed by Parker and others, and the observational models of Babcock and Leighton have been examined, with the conclusion that the dynamo theory is not applicable to the Sun and that the models fail.An essential part of the theory is an adequate effective diffusion coefficient. Fields are continuously sheared and amplified and, in this theory, these may not be allowed to accumulate; all subsurface fields of an old cycle must be eliminated. Ohmic diffusion is negligible and turbulent diffusion is invoked. However, this requires that all solar fields are tangled to a small scale, which is contrary to observation; for Hale's polarity laws are strictly observed, and large-scale surface features are common at the end of an 11-yr cycle in the same general area where new fields are appearing.The erupted (sunspot) fields lie generally above the unerupted, toroidal fields so that, even if they are merged as required, the centroid of the new system would be above that of the old. The result is not a steady-state oscillator, as required, but the complete loss of the solar field.It is concluded that for these and other reasons a shallow, reversing field is unacceptable, and that a deeply penetrating field is required. Reference is made to an alternative theory of the solar cycle based on a deep magnetic field. 相似文献
20.
A stochastic prediction model for the sunspot cycle is proposed. The prediction model is based on a modified binary mixture
of Laplace distribution functions and a moving-average model over the estimated model parameters. A six-parameter modified
binary mixture of Laplace distribution functions is used for the modeling of the shape of a generic sunspot cycle. The model
parameters are estimated for 23 sunspot cycles independently, and the primary prediction-model parameters are derived from
these estimated model parameters using a moving-average stochastic model. A correction factor (hump factor) is introduced
to make an initial prediction. The hump factor is computed for a given sunspot cycle as the ratio of the model estimated after
the completion of a sunspot cycle (post-facto model) and the prediction of the moving-average model. The hump factors can be applied one at a time over the moving-average
prediction model to get a final prediction of a sunspot cycle. The present model is used to predict the characteristics of
Sunspot Cycle 24. The methodology is validated using the previous Sunspot Cycles 21, 22, and 23, which shows the adequacy
and the applicability of the prediction model. The statistics of the variations of sunspot numbers at high solar activity
are used to provide the lower and upper bound for the predictions using the present model. 相似文献