共查询到20条相似文献，搜索用时 31 毫秒
1.
R. P. Kane 《Solar physics》2007,243(2):205-217
For many purposes (e.g., satellite drag, operation of power grids on Earth, and satellite communication systems), predictions of the strength of
a solar cycle are needed. Predictions are made by using different methods, depending upon the characteristics of sunspot cycles.
However, the method most successful seems to be the precursor method by Ohl and his group, in which the geomagnetic activity
in the declining phase of a sunspot cycle is found to be well correlated with the sunspot maximum of the next cycle. In the
present communication, the method is illustrated by plotting the 12-month running means aa(min ) of the geomagnetic disturbance index aa near sunspot minimum versus the 12-month running means of the sunspot number Rz near sunspot maximum [aa(min ) versus Rz(max )], using data for sunspot cycles 9 – 18 to predict the Rz(max ) of cycle 19, using data for cycles 9 – 19 to predict Rz(max ) of cycle 20, and so on, and finally using data for cycles 9 – 23 to predict Rz(max ) of cycle 24, which is expected to occur in 2011 – 2012. The correlations were good (∼+0.90) and our preliminary predicted
Rz(max ) for cycle 24 is 142±24, though this can be regarded as an upper limit, since there are indications that solar minimum
may occur as late as March 2008. (Some workers have reported that the aa values before 1957 would have an error of 3 nT; if true, the revised estimate would be 124±26.) This result of the precursor
method is compared with several other predictions of cycle 24, which are in a very wide range (50 – 200), so that whatever
may be the final observed value, some method or other will be discredited, as happened in the case of cycle 23. 相似文献
2.
A new index, the cumulative difference of sunspot activity in the northern and southern hemispheres, respectively, is proposed
to describe the long-term behavior of the North – South asymmetry of sunspot activity and to show the balance (or bias) of
sunspot activity in the two solar hemispheres on a long-term scale. Sunspot groups and sunspot areas from June 1874 to January
2007 are used to show the advantage of the index. The index clearly shows a long-term characteristic time scale of about 12
cycles in the North – South asymmetry of sunspot activity. Sunspot activity is found to dominate in the southern hemisphere
in cycle 23, and in cycle 24 it is predicted to dominate still in the southern hemisphere. A comparison of the new index with
other similar indexes is also given. 相似文献
3.
R. Arlt 《Solar physics》2008,247(2):399-410
Original drawings by J.C. Staudacher made in the period of 1749 – 1796 were digitized. The drawings provide information about
the size of the sunspots and are therefore useful for analyses sensitive to sunspot area rather than Wolf numbers. The total
sunspot area as a function of time is shown for the observing period. The sunspot areas measured do not support the proposition
of a weak, “lost” cycle between cycles 4 and 5. We also evaluate the usefulness of the drawings for the determination of sunspot
positions for future studies. 相似文献
4.
This paper presents a new approach for describing the shape of 11-year sunspot cycles by considering the monthly averaged
values. This paper also brings out a prediction model based on the analysis of 22 sunspot cycles from the year 1749 onward.
It is found that the shape of the sunspot cycles with monthly averaged values can be described by a functional form of modified
binary mixture of Laplace density functions, modified suitably by introducing two additional parameters in the standard functional
form. The six parameters, namely two locations, two scales, and two area parameters, characterize this model. The nature of
the estimated parameters for the sunspot cycles from 1749 onward has been analyzed and finally we arrived at a sufficient
set of the parameters for the proposed model. It is seen that this model picks up the sunspot peaks more closely than any
other model without losing the match at other places at the same time. The goodness of fit for the proposed model is also
computed with the Hathaway – Wilson – Reichmann
measure, which shows, on average, that the fitted model passes within 0.47 standard deviations of the actual averaged monthly
sunspot numbers. 相似文献
5.
In the present study, the short-term periodicities in the daily data of the sunspot numbers and areas are investigated separately
for the full disk, northern, and southern hemispheres during Solar Cycle 23 for a time interval from 1 January 2003 to 30
November 2007 corresponding to the descending and minimum phase of the cycle. The wavelet power spectrum technique exhibited
a number of quasi-periodic oscillations in all the datasets. In the high frequency range, we find a prominent period of 22 – 35
days in both sunspot indicators. Other quasi-periods in the range of 40 – 60, 70 – 90, 110 – 130, 140 – 160, and 220 – 240
days are detected in the sunspot number time series in different hemispheres at different time intervals. In the sunspot area
data, quasi-periods in the range of 50 – 80, 90 – 110, 115 – 130, 140 – 155, 160 – 190, and about 230 days were noted in different
hemispheres within the time period of analysis. The present investigation shows that the well-known “Rieger periodicity” of
150 – 160 days reappears during the descending phase of Solar Cycle 23, but this is prominent mainly in the southern part
of the Sun. Possible explanations of these observed periodicities are delivered on the basis of earlier results detected in
photospheric magnetic field time series (Knaack, Stenflo, and Berdyugina in Astron. Astrophys.
438, 1067, 2005) and solar r-mode oscillations. 相似文献
6.
Precursor techniques, in particular those using geomagnetic indices, often are used in the prediction of the maximum amplitude
for a sunspot cycle. Here, the year 2008 is taken as being the sunspot minimum year for cycle 24. Based on the average aa index value for the year of the sunspot minimum and the preceding four years, we estimate the expected annual maximum amplitude
for cycle 24 to be about 92.8±19.6 (1-sigma accuracy), indicating a somewhat weaker cycle 24 as compared to cycles 21 – 23.
Presuming a smoothed monthly mean sunspot number minimum in August 2008, a smoothed monthly mean sunspot number maximum is
expected about October 2012±4 months (1-sigma accuracy). 相似文献
7.
8.
Fluctuations of Solar Activity during the Declining Phase of the 11-Year Sunspot Cycle 总被引：1，自引：0，他引：1
R. P. Kane 《Solar physics》2009,255(1):163-168
The number of coronal mass ejections (CMEs) erupting from the Sun follows a trend similar to that of sunspot numbers during
the rising and maximum phase of the solar cycle. In the declining phase, the CME number has large fluctuations, dissimilar
to those of sunspot numbers. In several studies of solar – interplanetary and solar – terrestrial relationships, the sunspot
numbers and the 2800-MHz flux (F10) are used as representative of solar activity. In the rising phase, this may be adequate,
but in the declining phase, solar parameters such as CMEs may have a different behaviour. Cosmic-ray Forbush decreases may
occur even when sunspot activity is low. Therefore, when studying the solar influence on the Earth, one has to consider that
although geomagnetic conditions at solar maximum will be disturbed, conditions at solar minimum may not be necessarily quiet. 相似文献
9.
R. S. Dabas Kavita Sharma Rupesh M. Das K. G. M. Pillai Parvati Chopra N. K. Sethi 《Solar physics》2008,250(1):171-181
Based on cycles 17 – 23, linear correlations are obtained between 12-month moving averages of the number of disturbed days
when Ap is greater than or equal to 25, called the Disturbance Index (DI), at thirteen selected times (called variate blocks
1, 2,… , each of six-month duration) during the declining portion of the ongoing sunspot cycle and the maximum amplitude of
the following sunspot cycle. In particular, variate block 9, which occurs just prior to subsequent cycle minimum, gives the
best correlation (0.94) with a minimum standard error of estimation of ± 13, and hindcasting shows agreement between predicted
and observed maximum amplitudes to about 10%. As applied to cycle 24, the modified precursor technique yields maximum amplitude
of about 124±23 occurring about 45±4 months after its minimum amplitude occurrence, probably in mid to late 2011. 相似文献
10.
H. Kiliç 《Solar physics》2009,255(1):155-162
The short-term periodicities in sunspot numbers, sunspot areas, and flare index data are investigated in detail using the
Date Compensated Discrete Fourier Transform (DCDFT) for the full disk of the Sun separately over the rising, the maximum,
and the declining portions of solar cycle 23 (1996 – 2006). While sunspot numbers and areas show several significant periodicities
in a wide range between 23.1 and 36.4 days, the flare index data do not exhibit any significant periodicity. The earlier conclusion
of Pap, Tobiska, and Bouwer (1990, Solar Phys.
129, 165) and Kane (2003, J. Atmos. Solar-Terr. Phys.
65, 1169), that the 27-day periodicity is more pronounced in the declining portion of a solar cycle than in the rising and maximum
ones, seems to be true for sunspot numbers and sunspot area data analyzed here during solar cycle 23. 相似文献
11.
The running cross-correlation coefficient between solar-cycle amplitudes and rise times at a certain cycle lag is found to
vary in time, when using the smoothed monthly-mean sunspot group numbers available for 1610 – 1995. It may be negative or
positive for different periods of time. The Waldmeier effect (in which the rise times decrease with amplitude) is also found
to be very weak for some cycles. This result represents an observational constraint on solar-dynamo models and can help us
better understand the long-term evolution of solar activity. 相似文献
12.
In this work we describe a technique developed to improve medium-term prediction methods of monthly smoothed sunspot numbers.
Each month, the predictions are updated using the last available observations (see the monthly output in real time at ). The improvement of the predictions is provided by applying an adaptive Kalman filter to the medium-term predictions obtained
by any other method, using the six-monthly mean values of sunspot numbers covering the six months between the last available
value of the 13-month running mean (the starting point for the predictions) and the “current time” (i.e. now). Our technique provides an effective estimate of the sunspot index at the current time. This estimate becomes the new
starting point for the updated prediction that is shifted six months ahead in comparison with the last available 13-month
running mean, and it provides an increase of prediction accuracy. Our technique has been tested on three medium-term prediction
methods that are currently in real-time operation: The McNish–Lincoln method (NGDC), the standard method (SIDC), and the combined
method (SIDC). With our technique, the prediction accuracy for the McNish–Lincoln method is increased by 17 – 30%, for the
standard method by 5 – 21% and for the combined method by 6 – 57%. 相似文献
13.
Following the progression of nonlinear dynamical system theory, many authors have used varied methods to calculate the fractal dimension and the largest Lyapunov exponent 1 of the sunspot numbers and to evaluate the character of the chaotic attractor governing solar activity. These include the Grassberger–Procaccia algorithm, the technique provided by Wolf et al., and the nonlinear forecasting approach based on the method of distinguishing between chaos and measurement errors in time series described by Sugihara and May. In this paper, we use the Grassberger–Procaccia algorithm to estimate the other character of the chaotic attractor. This character is time scale of a transition from high-dimensional or stochastic at shorter times to a low-dimensional chaotic behavior at longer times. We find that the transitional time scale in the monthly mean sunspot numbers is about 8 yr; the low-dimensional chaotic behavior operates at time scales longer than about 8 yr and a high-dimensional or stochastic process operates at time scales shorter than about 8 yr. 相似文献
14.
In the previous study (Dabas et al. in Solar Phys.
250, 171, 2008), to predict the maximum sunspot number of the current solar cycle 24 based on the geomagnetic activity of the preceding
sunspot minimum, the Ap index was used which is available from the last six to seven solar cycles. Since a longer series of the aa index is available for more than the last 10 – 12 cycles, the present study utilizes aa to validate the earlier prediction. Based on the same methodology, the disturbance index (DI), which is the 12-month moving
average of the number of disturbed days (aa≥50), is computed at thirteen selected times (called variate blocks 1,2,…,13; each of them in six-month duration) during the
declining portion of the ongoing sunspot cycle. Then its correlation with the maximum sunspot number of the following cycle
is evaluated. As in the case of Ap, variate block 9, which occurs exactly 48 months after the current cycle maximum, gives the best correlation (R=0.96) with a minimum standard error of estimation (SEE) of ± 9. As applied to cycle 24, the aa index as precursor yields the maximum sunspot number of about 120±16 (the 90% prediction interval), which is within the 90%
prediction interval of the earlier prediction (124±23 using Ap). Furthermore, the same method is applied to an expanded range of cycles 11 – 23, and once again variate block 9 gives the
best correlation (R=0.95) with a minimum SEE of ± 13. The relation yields the modified maximum amplitude for cycle 24 of about 131±20, which
is also close to our earlier prediction and is likely to occur at about 43±4 months after its minimum (December 2008), probably
in July 2012 (± 4 months). 相似文献
15.
Miyoshi Suzuki 《Solar physics》2012,278(2):257-267
We studied the solar rotation rate and its temporal change, using the sunspot data obtained during activity cycle 23 (1996 – 2006).
The equatorial rotation rate is nearly the same as in the former cycle 22, while the latitudinal gradient of differential
rotation considerably increased. Comparison of our results with others indicates the existence of a long-term periodicity
of about eight cycles in differential rotation. In addition, no significant asymmetry in differential rotation between the
northern and southern hemispheres during cycle 23 was found. The equatorial rotation rate and the latitudinal gradient of
the differential rotation in the period of cycle 23 are approximately constant, except for the initial and final phases in
the cycle. 相似文献
16.
Mykola I. Pishkalo 《Solar physics》2006,233(2):277-290
We have investigated the correlation between the relative sunspot number and tilt of the heliospheric current sheet (HCS)
in solar cycles 21–23. Strong and highly significant positive correlation (r > 0.8, P < 0.001) was found for corresponding data in the time interval from May 1976 through December 2004. Cross-correlation analysis
does not reveal any time shift between the data sets. Reconstructed values of the HCS tilt, for the time interval before 1976,
are found using sunspot numbers. To take different amplitude of solar cycles into account they were then normalized to zero
in the minima of the solar activity and to average in solar cycles 21–23 maximal calculated HCS tilt in the maxima. These
normalized reconstructed HCS data are compared with the angular positions of the brightest coronal streamers observed during
total solar eclipses in 1870–2002, and their agreement is better for the minima of the solar activity than for the maxima. 相似文献
17.
Recently, Juckett and Wolff (Solar Phys.
252, 247, 2008) showed that the timing and longitude of sunspot patterns has some correspondence with a model based on coupled g modes. The model maximizes the nonlinear coupling of those g modes sharing harmonic degree ℓ to generate a “set(ℓ)” that assists its own excitation by locally enhancing nuclear burning. Each set(ℓ) has oscillatory power concentrated at two longitudes, on opposite sides of the Sun and drifts slowly retrograde within the
radiative zone (RZ) at a rate that depends on ℓ. When the strong longitudes of two or more sets overlap, wave dissipation adds extra energy to that locality at the base
of the convective envelope increasing convection and then sunspot activity. We compare the main subdecadal sunspot frequencies
with the intersections of sets derived from ℓ=2 – 11 and G, where G represents unresolvable high-ℓ modes that rotate similarly to the RZ. After determining the set(ℓ) spatial phases, we show that 17 subdecadal oscillations with periods in the range 0.6 to 7.0 years (4.5 to 50 nHz), generated
by 23 unique intersections of the 11 sets, are synchronous with 17 corresponding frequencies in the sunspot time series. After
optimizing parameters, we find a mean correlation of 0.96 for synchrony among the 17 waveform pairs. These 17 frequencies
constitute the bulk of the non-noise subdecadal frequency domain of the sunspot variation. We conclude that the sunspot series
contains oscillatory components with the same temporal phases and frequencies as various set(ℓ) intersections spanning the past ≈ 100 years. This additional evidence for the role of coupled g modes in sunspot dynamics suggests that more of sunspot variability can be understood with nonmagnetic fluid mechanics than
popularly thought. 相似文献
18.
The north – south asymmetries (NSA) of three solar activity indices are derived and mutually compared over a period of more
than five solar cycles (1945 – 2001). A catalogue of the hemispheric sunspot numbers, the data set of the coronal green line
brightness developed by us, and the magnetic flux derived from the NSO/KP data (1975 – 2001) are treated separately within
the discrete low- and mid-latitude zones (5° – 30°, 35° – 60°). The calculated autocorrelations, cross-correlations, and regressions
between the long-term NSA data sets reveal regularities in the solar activity phenomenon. Namely, the appearance of a distinct
quasi-biennial oscillation (QBO) is evident in all selected activity indices. Nevertheless, a smooth behavior of QBO is derived
only when sufficient temporal averaging is performed over solar cycles. The variation in the significance and periodicity
of QBO allows us to conclude that the QBO is not persistent over the whole solar cycle. A similarity in the photospheric and
coronal manifestations of the NSA implies that their mutual relation will also show the QBO. A roughly two-year periodicity
is actually obtained, but again only after significant averaging over solar cycles. The derived cross-correlations are in
fact variable in degree of correlation as well as in changing periodicity. A clear and significant temporal shift of 1 – 2
months in the coronal manifestation of the magnetic flux asymmetry relative to the photospheric manifestation is revealed
as a main property of their mutual correlation. This shift can be explained by the delayed large-scale coronal manifestation
in responding to the emergence of the magnetic flux in the photosphere. The reliability of the derived results was confirmed
by numerical tests performed by selecting different numerical values of the used parameters. 相似文献
19.
L. A. Plyusnina 《Solar physics》2010,261(2):223-232
There are two types of active longitudes (ALs) in terms of the distribution of sunspot areas: long-lived and intra-cyclic
ALs. The rotation period of the long-lived ALs has been determined by a new method in this paper. The method is based on the
property of ALs to be maintained over several cycles of solar activity. The daily values of sunspot areas for 1878 – 2005
are analyzed. It is shown that the AL positions remain almost constant over a period of about ten cycles, from cycle 13 to
cycle 22. The rotation period was found to be 27.965 days during this period. The dispersion in AL positions is about 26°
from cycle to cycle, which is half of the dispersion observed in the Carrington system. The ALs in the growth phase of the
activity cycle are more stable and pronounced. The excess in solar activity in the ALs over adjacent longitudinal intervals
is about 12 – 14%. It is shown that only one long-lived AL can be observed at one time on the Sun, as a rule. 相似文献
20.
J. Javaraiah 《Solar physics》2011,270(2):463-483
Using the combined Greenwich (1874 – 1976) and Solar Optical Observatories Network (1977 – 2009) data on sunspot groups, we
study the long-term variations in the mean daily rates of growth and decay of sunspot groups. We find that the minimum and
the maximum values of the annually averaged daily mean growth rates are ≈ 52% day−1 and ≈ 183% day−1, respectively, whereas the corresponding values of the annually averaged daily mean decay rates are ≈ 21% day−1 and ≈ 44% day−1, respectively. The average value (over the period 1874 – 2009) of the growth rate is about 70% more than that of the decay
rate. The growth and the decay rates vary by about 35% and 13%, respectively, on a 60-year time scale. From the beginning
of Cycle 23 the growth rate is substantially decreased and near the end (2007 – 2008) the growth rate is lowest in the past
about 100 years. In the extended part of the declining phase of this cycle, the decay rate steeply increased and it is largest
in the beginning of the current Cycle 24. These unusual properties of the growth and the decay rates during Cycle 23 may be
related to cause of the very long declining phase of this cycle with the unusually deep and prolonged current minimum. A ≈ 11-year
periodicity in the growth and the decay rates is found to be highly latitude and time dependent and seems to exist mainly
in the 0° – 10° latitude interval of the southern hemisphere. The strength of the known approximate 33 – 44-year modulation
in the solar activity seems to be related to the north-south asymmetry in the growth rate. Decreasing and increasing trends
in the growth and the decay rates indicate that the next 2 – 3 solar cycles will be relatively weak. 相似文献