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1.
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
2.
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
3.
According to research results from solar-dynamo models, the northern and southern hemispheres may evolve separately throughout
the solar cycle. The observed phase lag between the northern and southern hemispheres provides information regarding how strongly
the hemispheres are coupled. Using hemispheric sunspot-area and sunspot-number data from Cycles 12 – 23, we determine how
out of phase the separate hemispheres are during the rising, maximum, and declining period of each solar cycle. Hemispheric
phase differences range from 0 – 11, 0 – 14, and 2 – 19 months for the rising, maximum, and declining periods, respectively.
The phases appear randomly distributed between zero months (in phase) and half of the rise (or decline) time of the solar
cycle. An analysis of the sunspot cycle double peak, or Gnevyshev gap, is conducted to determine if the double-peak is caused
by the averaging of two hemispheres that are out of phase. We confirm previous findings that the Gnevyshev gap is a phenomenon
that occurs in the separate hemispheres and is not due to a superposition of sunspot indices from hemispheres slightly out
of phase. Cross hemispheric coupling could be strongest at solar minimum, when there are large quantities of magnetic flux
at the Equator. We search for a correlation between the hemispheric phase difference near the end of the solar cycle and the
length of solar-cycle minimum, but found none. Because magnetic flux diffusion across the Equator is a mechanism by which
the hemispheres couple, we measured the magnetic flux crossing the Equator by examining Kitt Peak Vacuum Telescope and SOLIS
magnetograms for Solar Cycles 21 – 23. We find, on average, a surplus of northern hemisphere magnetic flux crossing during
the mid-declining phase of each solar cycle. However, we find no correlation between magnitude of magnetic flux crossing the
Equator, length of solar minima, and phase lag between the hemispheres. 相似文献
4.
L. H. Deng J. Y. Song Y. Y. Xiang Y. K. Tang 《Journal of Astrophysics and Astronomy》2011,32(3):401-409
The monthly sunspot numbers compiled by Temmer et al. and the monthly polar faculae from observations of the National Astronomical Observatory of Japan, for the interval of March
1954 to March 1996, are used to investigate the phase relationship between polar faculae and sunspot activity for total solar
disk and for both hemispheres in solar cycles 19, 20, 21 and 22. We found that (1) the polar faculae begin earlier than sunspot
activity, and the phase difference exhibits a consistent behaviour for different hemispheres in each of the solar cycles,
implying that this phenomenon should not be regarded as a stochastic fluctuation; (2) the inverse correlation between polar
faculae and sunspot numbers is not only a long-term behaviour, but also exists in short time range; (3) the polar faculae
show leads of about 50–71 months relative to sunspot numbers, and the phase difference between them varies with solar cycle;
(4) the phase difference value in the northern hemisphere differs from that in the southern hemisphere in a solar cycle, which
means that phase difference also existed between the two hemispheres. Moreover, the phase difference between the two hemispheres
exhibits a periodical behaviour. Our results seem to support the finding of Hiremath (2010). 相似文献
5.
Neeraj Singh Bankoti Navin Chandra Joshi Seema Pande Bimal Pande Kavita Pandey 《New Astronomy》2010,15(6):561-568
A study on north–south (N–S) asymmetry of different solar activity features (DSAF) such as solar proton events, solar active prominences [total, low (?40°) and high (?50°) latitudes], Hα flare indices, soft X-ray flares, monthly mean sunspot areas and monthly mean sunspot numbers carried out from May 1996 to October 2008. Study shows a southern dominance of DSAF during this period. During the rising phase of the cycle 23 the number of DSAF approximately equals on both, the northern and the southern hemispheres. But these activities tend to shift from northern to southern hemisphere during the period 1998–1999. The statistical significance of the asymmetry time series using a χ2-test of goodness of fit indicates that in most of the cases the asymmetry is highly significant, meaning thereby that the asymmetry is a real feature in the N–S distribution of DSAF. 相似文献
6.
7.
X. L. Yan L. H. Deng Z. Q. Qu C. L. Xu D. F. Kong 《Journal of Astrophysics and Astronomy》2012,33(4):387-397
To understand better the variation of solar activity indicators originated at different layers of the solar atmosphere with respect to sunspot cycles, we carried out a study of phase relationship between sunspot number, flare index and solar radio flux at 2800 MHz from January 1966 to May 2008 by using cross-correlation analysis. The main results are as follows: (1) The flare index and sunspot number have synchronous phase for cycles 21 and 22 in the northern hemisphere and for cycle 20 in the southern hemisphere. (2) The flare index has a noticeable time lead with respect to sunspot number for cycles 20 and 23 in the northern hemisphere and for cycles 22 and 23 in the southern hemisphere. (3) For the entire Sun, the flare index has a noticeable time lead for cycles 20 and 23, a time lag for cycle 21, and no time lag or time lead for cycle 22 with respect to sunspot number. (4) The solar radio flux has a time lag for cycles 22 and 23 and no time lag or time lead for cycles 20 and 21 with respect to sunspot number. (5) For the four cycles, the sunspot number and flare index in the northern hemisphere are all leading to the ones in the southern hemisphere. These results may be instructive to the physical processes of flare energy storage and dissipation. 相似文献
8.
We study the solar cycle evolution during the last 8 solar cycles using a vectorial sunspot area called the LA (longitudinal asymmetry) parameter. This is a useful measure of solar activity in which the stochastic, longitudinally evenly distributed sunspot activity is reduced and which therefore emphasizes the more systematic, longitudinally asymmetric sunspot activity. Interesting differences are found between the LA parameter and the more conventional sunspot activity indices like the (scalar) sunspot area and the sunspot number. E.g., cycle 19 is not the highest cycle according to LA. We have calculated the separate LA parameters for the northern and southern hemisphere and found a systematic dipolar-type oscillation in the dominating hemisphere during high solar activity times which is reproduced from cycle to cycle. We have analyzed this oscillation during cycles 16–22 by a superposed epoch method using the date of magnetic reversal in the southern hemisphere as the zero epoch time. According to our analysis, the oscillation starts by an excess of the northern LA value in the ascending phase of the solar cycle which lasts for about 2.3 years. Soon after the maximum northern dominance, the southern hemisphere starts dominating, reaching its minimum some 1.2–1.7 years later. The period of southern dominance lasts for about 1.6 years and ends, on an average, slightly before the end of magnetic reversal. 相似文献
9.
We have analyzed the asymmetry of sunspot areas during the current solar cycle 22, finding that it has been statistically significant and that the shape of the underlying trend within the full asymmetry time series (1874–1993) indicates that the dominance of solar activity has started to shift, during the current cycle, from the northern hemisphere to the southern one. 相似文献
10.
Li Kejun Gu Xiaoma Xiang Fuyuan Liu Xiaohua Chen Xuekun 《Monthly notices of the Royal Astronomical Society》2000,317(4):897-901
Data of sunspot groups at high latitude (35°), from the year 1874 to the present (2000 January), are collected to show their evolutional behaviour and to investigate features of the yearly number of sunspot groups at high latitude. Subsequently, an evolutional pattern of sunspot group number at high latitude is given in this paper. Results obtained show that the number of sunspot groups of a solar cycle at high latitude rises to a maximum value about 1 yr earlier than the time of the maximum of sunspot relative numbers of the solar cycle, and then falls to zero more rapidly. The results also show that, at the moment, solar activity described by the sunspot relative numbers has not yet reached its minimum. In general, sunspot groups at high latitude have not appeared on the solar disc during the last 3 yr of a Wolf solar cycle. The asymmetry of the high latitude sunspot group number of a Wolf solar cycle can reflect the asymmetry of solar activity in the Wolf solar cycle, and it is suggested that one could further use the high latitude sunspot group number during the rising time of a Wolf solar cycle, maximum year included, to judge the asymmetry of solar activity over the whole solar cycle. 相似文献
11.
R. P. Kane 《Solar physics》2007,245(2):415-421
The occurrence of double peaks near the maximum of sunspot activity was first emphasized by Gnevyshev (Solar Phys.
1, 107, 1967) for the peak years of solar cycle 19 (1954 – 1964). In the present analysis, it is shown that double peaks in sunspot numbers
were clearly visible in solar latitudes 10 – 30° N but almost absent in the southern latitudes, where some single peaks were
observed out of phase by several months from any of the peaks in the northern latitudes. The spacing between the double peaks
increased from higher to lower northern latitudes, hinting at latitudinal migration. In the next cycle 20 (1965 – 1976), which
was of about half the strength of cycle 19, no clear-cut double peaks were seen, and the prominent peak in the early part
of 1967 in the northern latitudes was seen a few months later in the southern latitudes. A direct relationship of Gnevyshev
peaks with changes in the solar polar magnetic fields seems to be dubious. The commencements do not match. 相似文献
12.
We have analysed a large set of sunspot group data (1874 – 2004) and find that the meridional flow strongly varies with the
phase of the solar cycle, and the variation is quite different in the northern and the southern hemispheres. We also find
the existence of considerable cycle-to-cycle variation in the meridional velocity, and about a 11-year difference between
the phases of the corresponding variations in the northern and the southern hemispheres. In addition, our analysis also indicates
the following: (i) the existence of a considerable difference (about 180°) between the phases of the solar-cycle variations in the latitude-gradient terms of the northern and the southern hemispheres’
rotations; (ii) the existence of correlation (good in the northern hemisphere and weak in the southern hemisphere) between the mean solar-cycle
variations of meridional flow and the latitude-gradient term of solar rotation; (iii) in the northern hemisphere, the cycle-to-cycle variation of the mean meridional velocity leads that of the equatorial rotation
rate by about 11 years, and the corresponding variations have approximately the same phase in the southern hemisphere; and
(iv) the directions of the mean meridional velocity is largely toward the pole in the longer sunspot cycles and largely toward
the equator in the shorter cycles. 相似文献
13.
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
14.
R. P. Kane 《Solar physics》2006,233(1):107-115
This paper examines the variations of coronal mass ejections (CMEs) and interplanetary CMEs (ICMEs) during solar cycle 23
and compares these with those of several other indices. During cycle 23, solar and interplanetary parameters had an increase
from 1996 (sunspot minimum) to ∼2000, but the interval 1998–2002 had short-term fluctuations. Sunspot numbers had peaks in
1998, 1999, 2000 (largest), 2001 (second largest), and 2002. Other solar indices had matching peaks, but the peak in 2000
was larger than the peak in 2001 only for a few indices, and smaller or equal for other solar indices. The solar open magnetic
flux had very different characteristics for different solar latitudes. The high solar latitudes (45∘–90∘) in both N and S hemispheres had flux evolutions anti-parallel to sunspot activity. Fluxes in low solar latitudes (0∘–45∘) evolved roughly parallel to sunspot activity, but the finer structures (peaks etc. during sunspot maximum years) did not
match with sunspot peaks. Also, the low latitude fluxes had considerable N–S asymmetry. For CMEs and ICMEs, there were increases
similar to sunspots during 1996–2000, and during 2000–2002, there was good matching of peaks. But the peaks in 2000 and 2001
for CMEs and ICMEs had similar sizes, in contrast to the 2000 peak being greater than the 2001 peak for sunspots. Whereas
ICMEs started decreasing from 2001 onwards, CMEs continued to remain high in 2002, probably due to extra contribution from
high-latitude prominences, which had no equivalent interplanetary ICMEs or shocks. Cosmic ray intensity had features matching
with those of sunspots during 2000–2001, with the 2000 peak (on a reverse scale, actually a cosmic ray decrease or trough)
larger than the 2001 peak. However, cosmic ray decreases started with a delay and ended with a delay with respect to sunspot
activity. 相似文献
15.
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
16.
The amplitude of a solar-activity cycle is found to be well correlated (r = −0.811) with the descending time three cycles earlier, in smoothed monthly-mean sunspot numbers for Cycles 8 – 23. The
descending time therefore can be used as one of the indicators to predict the amplitudes. As a result, the amplitudes of Cycles
24 – 25 are estimated to be 114.8 ± 17.4, 111.6 ± 17.4, respectively, where the error bar equals ± standard error. 相似文献
17.
Long-term variations in north-south asymmetry of solar activity 总被引：1，自引：0，他引：1
We present a new set of data on relative sunspot number (total, northern hemisphere, and southern hemisphere), taken for the 37-yr period 1947 to 1983; this constitutes a particularly coherent and consistent set of data, taken by the same observer (Hisako Koyama) using the same observing instrument. These data are combined with earlier data (White and Trotter, 1977) on the variation of sunspot areas for both solar hemispheres from 1874 to 1971. The combined data, covering 110 years and 10 solar cycles, are examined for periodicity in solar activity north-south asymmetry. We show that, in general, northern hemisphere activity, displayed as either An/(An + As) or Rn/(Rn + Rs), peaks about two years after sunspot minimum. This peak is greater during even cycles, pointing to a 22-yr periodicity in north-south asymmetry in solar activity, suggesting that the asymmetry is related to the 22-yr solar magnetic cycle. We demonstrate that the largest and most protracted period of northern-hemisphere activity excess in the last 110 years has occurred from 1959 to 1970; we show that there is a strong correlation between northern activity excess and a cosmic-ray density gradient perpendicular to the ecliptic plane, pointing southward, which is evident in cosmic-ray diurnal variation data from the Embudo underground cosmic-ray telescope. 相似文献
18.
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
19.
As an important measurement parameter, global total electron content (TEC) is appropriate for the study of the Sun–Earth connection.
In this paper, the wavelet technique is employed to investigate the periodicities in global mean TEC during 1995–2008. Analysis
results show several remarkable components (including 27-day, semiannual and annual cycles) existing in global mean TEC with
obvious time-variable characteristics, besides 11-year cycle. After analyzing sunspot numbers and solar extreme ultra-violet
(EUV) radiation variations during this time period, except for semiannual variations, close correlation between global mean
TEC and solar variations is found, especially, a strong resemblance of the 27-day fluctuation exists in global mean TEC, sunspot
and solar EUV radiation variations. 相似文献
20.
K. M. Hiremath 《Journal of Astrophysics and Astronomy》2006,27(2-3):367-372
We use 130 years data for studying correlative effects due to solar cycle and activity phenomena on the occurrence of rainfall
over India. For the period of different solar cycles, we compute the correlation coefficients and significance of correlation
coefficients for the seasonal months of Jan–Feb (JF), Mar–May (MAM), June–Sept (JJAS) and Oct–Dec (OND) and,annual mean data. We find that: (i) with a moderate-to-high significance, Indian rainfall is correlated with the sunspot activity and,
(ii) there is an overall trend that during the period of low sunspot activity, occurrence of rainfall is high compared to
the period of high sunspot activity.
We speculate in this study a possible physical connection between the occurrence of the rainfall and the sunspot activities
and, the flux of galactic cosmic rays. Some of the negative correlations between the occurrences of the sunspot and rainfall
activities obtained for different solar cycle periods are interpreted as effects of aerosols on the rain forming clouds due
to either intermittent volcanic eruptions or due to intrusion of interstellar dust particles in the Earth’s atmosphere. 相似文献