共查询到20条相似文献，搜索用时 671 毫秒
1.
To better understand long-term flare activity, we present a statistical study on soft X-ray flares from May 1976 to May 2008.
It is found that the smoothed monthly peak fluxes of C-class, M-class, and X-class flares have a very noticeable time lag
of 13, 8, and 8 months in cycle 21 respectively with respect to the smoothed monthly sunspot numbers. There is no time lag
between the sunspot numbers and M-class flares in cycle 22. However, there is a one-month time lag for C-class flares and
a one-month time lead for X-class flares with regard to sunspot numbers in cycle 22. For cycle 23, the smoothed monthly peak
fluxes of C-class, M-class, and X-class flares have a very noticeable time lag of one month, 5 months, and 21 months respectively
with respect to sunspot numbers. If we take the three types of flares together, the smoothed monthly peak fluxes of soft X-ray
flares have a time lag of 9 months in cycle 21, no time lag in cycle 22 and a characteristic time lag of 5 months in cycle
23 with respect to the smoothed monthly sunspot numbers. Furthermore, the correlation coefficients of the smoothed monthly
peak fluxes of M-class and X-class flares and the smoothed monthly sunspot numbers are higher in cycle 22 than those in cycles
21 and 23. The correlation coefficients between the three kinds of soft X-ray flares in cycle 22 are higher than those in
cycles 21 and 23. These findings may be instructive in predicting C-class, M-class, and X-class flares regarding sunspot numbers
in the next cycle and the physical processes of energy storage and dissipation in the corona. 相似文献
2.
Asok K. Sen 《Solar physics》2007,241(1):67-76
In this paper we use the notion of multifractality to describe the complexity in Hα flare activity during the solar cycles 21, 22, and 23. Both northern and southern hemisphere flare indices are analyzed. Multifractal behavior of the flare activity is characterized by calculating the singularity spectrum of the daily flare index time series in terms of the Hölder exponent. The broadness of the singularity spectrum gives a measure of the degree of multifractality or complexity in the flare index data. The broader the spectrum, the richer and more complex is the structure with a higher degree of multifractality. Using this broadness measure, complexity in the flare index data is compared between the northern and southern hemispheres in each of the three cycles, and among the three cycles in each of the two hemispheres. Other parameters of the singularity spectrum can also provide information about the fractal properties of the flare index data. For instance, an asymmetry to the left or right in the singularity spectrum indicates a dominance of high or low fractal exponents, respectively, reflecting a relative abundance of large or small fluctuations in the total energy emitted by the flares. Our results reveal that in the even (22nd) cycle the singularity spectra are very similar for the northern and southern hemispheres, whereas in the odd cycles (21st and 23rd) they differ significantly. In particular, we find that in cycle 21, the northern hemisphere flare index data have higher complexity than its southern counterpart, with an opposite pattern prevailing in cycle 23. Furthermore, small-scale fluctuations in the flare index time series are predominant in the northern hemisphere in the 21st cycle and are predominant in the southern hemisphere in the 23rd cycle. Based on these findings one might suggest that, from cycle to cycle, there exists a smooth switching between the northern and southern hemispheres in the multifractality of the flaring process. This new observational result may bring an insight into the mechanisms of the solar dynamo operation and may also be useful for forecasting solar cycles. 相似文献
3.
4.
In this work we study the mid-term periodicities (MTPs), between 1 and 2 years, of the sunspot groups and the flare index (FI), by separating the data into hemispheres and spectral bands (SBs) according to the most significant periodicities presented by these phenomena. We found that the MTP of sunspot groups has a diminished power during the Modern Minimum and an increased power during the Modern Maximum, with the exception of cycle 20. For flares, the MTP has a diminished power during the low activity cycle 20, and an increased power during cycles 21 and 22. Therefore, for both sunspot groups and FI, cycle 20 shows a very diminished power followed by the active and higher-power cycles 21 and 22; cycle 23 shows a weaker power than cycles 21 and 22. It is uncertain whether MTP can be a precursor of a long-term minimum of solar activity or not, as has been previously suggested. Also, there is no one-to-one correlation between the cycle intensity and the importance of MTP. Concerning the quasi-biennial periodicities and the theory of two kinds of dynamos, we notice the tendency that higher-power cycles mean weaker coupling in the model. Concerning the hemispheric north-south asymmetry, for sunspot groups the southern hemisphere dominates in most of the SBs, while for FI the northern hemisphere dominates for all the SBs. Additionally, the time lag found between the two hemispheres indicates that the degrees of coupling in the photosphere for sunspot groups and in the corona for flares are between moderate and strong. Finally, the modulation shown by the MTP time series suggests that these periodicities are the product of chaotic quasi-periodic processes and not of stochastic processes. 相似文献
5.
In this paper, the monthly counts of flare index in the northern and southern hemispheres are used to investigate the hemispheric variation of the flare index in each of solar cycles 20–23. It is found that, (1) the flare index is asymmetrically distributed in each solar cycle and its asymmetry is a real phenomenon; (2) the flare index in the northern hemisphere begins earlier than that in the southern hemisphere in each of solar cycles 20–23, and the phase shifts between the two hemispheres show an odd‐even pattern; (3) although the flare index dominating in a hemisphere does not mean that it leads in phase in this hemisphere in individual solar cycle, these two features have an intrinsic relationship. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Recently, Wheatland and Litvinenko (2001) have suggested that over the solar cycle both the flaring rate and the magnetic free energy in the corona lag behind the energy supply to the system. To test this model result, we analyzed the evolution of solar flare occurrence with regard to sunspot numbers (as well as sunspot areas), using H flare data available for the period 1955–2002, and soft X-ray flare data (GOES 1–8 Å) for the period 1976–2002. For solar cycles 19, 21, and 23, we find a characteristic time lag between flare activity and sunspot activity in the range 1015 months, consistent with the model predictions by Wheatland and Litvinenko (2001). The phenomenon turns out to be more prominent for highly energetic flares. The investigation of solar activity separately for the northern and southern hemisphere allows us to exclude any bias due to overlapping effects from the activity of both hemispheres and confirms the dynamic relevance of the delay phenomenon. Yet, no characteristic time lag >0 is found for solar cycles 20 and 22. The finding that in odd-numbered cycles flare activity is statistically delayed with respect to sunspot activity, while in even-numbered cycles it is not, suggests a connection to the 22-year magnetic cycle of the Sun. Further insight into the connection to the 22-year magnetic cycle could possibly be gained when a 22-year variation in the energy supply rate is taken into account in the Wheatland and Litvinenko (2001) model. The existence of a 22-year modulation in the energy supply rate is suggested by the empirical Gnevyshev – Ohl rule, and might be caused by a relic solar field. 相似文献
7.
During sunspot cycles 20 and 21, the maximum in smoothed 10.7-cm solar radio flux occurred about 1.5 yr after the maximum smoothed sunspot number, whereas during cycles 18 and 19 no lag was observed. Thus, although 10.7-cm radio flux and Zürich suspot number are highly correlated, they are not interchangeable, especially near solar maximum. The 10.7-cm flux more closely follows the number of sunspots visible on the solar disk, while the Zürich sunspot number more closely follows the number of sunspot groups. The number of sunspots in an active region is one measure of the complexity of the magnetic structure of the region, and the coincidence in the maxima of radio flux and number of sunspots apparently reflects higher radio emission from active regions of greater magnetic complexity. The presence of a lag between sunspot-number maximum and radio-flux maximum in some cycles but not in others argues that some aspect of the average magnetic complexity near solar maximum must vary from cycle to cycle. A speculative possibility is that the radio-flux lag discriminates between long-period and short-period cycles, being another indicator that the solar cycle switches between long-period and short-period modes.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
8.
V. K. Verma 《Journal of Astrophysics and Astronomy》2000,21(3-4):173-176
We report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during
solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data
for the period 1936-1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998.
Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena
during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar
cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested
by Verma. 相似文献
9.
Using the smoothed time series of maximum CME speed index for solar cycle 23, it is found that this index, analyzed jointly with six other solar activity indicators, shows a hysteresis phenomenon. The total solar irradiance, coronal index, solar radio flux (10.7?cm), Mg?ii core-to-wing ratio, sunspot area, and H?? flare index follow different paths for the ascending and the descending phases of solar cycle?23, while a saturation effect exists at the maximum phase of the cycle. However, the separations between the paths are not the same for the different solar activity indicators used: the H?? flare index and total solar irradiance depict broad loops, while the Mg?ii core-to-wing ratio and sunspot area depict narrow hysteresis loops. The lag times of these indices with respect to the maximum CME speed index are discussed, confirming that the hysteresis represents a clue in the search for physical processes responsible for changing solar emission. 相似文献
10.
In this paper, we investigate the spatial distribution of solar flares in the northern and southern hemispheres of the Sun
that occurred during the period 1996 to 2003. This period of investigation includes the ascending phase, the maximum and part
of the descending phase of solar cycle 23. It is revealed that the flare activity during this cycle is low compared to the
previous solar cycle, indicating the violation of Gnevyshev-Ohl rule. The distribution of flares with respect to heliographic
latitudes shows a significant asymmetry between northern and southern hemisphere which is maximum during the minimum phase
of the solar cycle. The present study indicates that the activity dominates the northern hemisphere in general during the
rising phase of the cycle (1997–2000). The dominance of northern hemisphere shifted towards the southern hemisphere after
the solar maximum in 2000 and remained there in the successive years. Although the annual variations in the asymmetry time
series during cycle 23 are quite different from cycle 22, they are comparable to cycle 21. 相似文献
11.
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
12.
V. K. Verma 《Solar physics》1988,114(1):185-188
The present paper investigates the north-south asymmetry for major flares (solar cycles 19 and 20), type II radio bursts (solar cycles 19,20 and 21), white light flares (solar cycle 19,20 and 21), and gamma ray bursts, hard X-ray bursts and coronal mass ejections (solar cycle 21). The results are compared with the found asymmetry in favour of the northern hemisphere during solar cycles 19 and 20 in favour of the southern hemisphere during solar cycle 21. 相似文献
13.
K. J. Li 《Solar physics》2009,255(1):169-177
Five solar-activity indices – the monthly-mean sunspot numbers from January 1945 to March 2008, the monthly-mean sunspot areas
during the period of May 1874 to March 2008, the monthly numbers of sunspot groups from May 1874 to May 2008, the monthly-mean
flare indices from January 1966 to December 2006, and the numbers of solar filaments per Carrington rotation in the time interval
of solar rotations 876 to 1823 – have been used to show a systematic time delay between northern and southern hemispheric
solar activities in a cycle. It is found that solar activity does not occur synchronously in the northern and southern hemispheres,
and there is a systematic time lag or lead (phase shift) between northern and southern hemispheric solar activity in a cycle.
About an eight-cycle period is inferred to exist in such phase shifts. The activity on the Sun may be governed by two different
and coupled processes, not by a single process. 相似文献
14.
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
15.
Wheatland and Litvinenko (2001) presented a model for dynamical energy balance in the flaring solar corona which predicts
a time lag between flare occurrence and the supply of energy to the corona (`driving'). They also suggested that an observed
net lag between flare numbers and sunspot numbers over cycles 21 and 22 might provide support for the model. Temmer, Veronig,
and Hanslmeier (2003) examined data for five individual solar cycles (19–23) and confirmed a lag between flare and sunspot
numbers for odd solar cycles, but found no lag for even cycles. Following the suggestion of Temmer, Veronig, and Hanslmeier,
the energy balance model is here extended to incorporate 22-year driving consistent with the phenomenological Gnevyshev—Ohl
rule. The model is found to exhibit a greater lag for the smaller (even) cycles, in contradiction with the findings of Temmer,
Veronig, and Hanslmeier. A modification to the model is investigated in which the flaring rate is proportional to the free
energy and to the driving rate for small driving rates, but is proportional only to the free energy for large driving rates.
The modified model can in principle account for the observations. 相似文献
16.
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
17.
YANG Xing-xing LE Gui-ming ZHANG Cheng-yi YIN Zhi-qiang ZHAO Wei 《Chinese Astronomy and Astrophysics》2014
The X1- and X2- or higher class ?ares in solar cycles 21, 22, and 23 from 1986 to 2008 have been analyzed statistically in this paper. It is found in the statistical study that the number of the X1-class ?ares accounted for 52.71% of total X- and higher class ?ares, while, the number of the X2- and higher class ?ares accounted for 47.29% of total X- and higher class ?ares. No matter whether the X1- and X2- or higher class ?ares, most of them occured in the descending phases of the solar cycles. Moreover, the weaker the intensity of the solar cycle, the higher the ratio of the ?ares occurred in the descending phase of the solar cycle, and the stronger the intensity of solar ?ares, the higher the ratio of the ?ares occurred in the descending phases of the solar cycles. In addition, the phase difference between the peak of the smoothed monthly mean number of sunspots and that of the X-class ?ares has been calculated, which shows that the smoothed monthly mean number of the X1-class ?ares had a very noticeable time advance of 1 month with respect to that of sunspots in the cycles 21 and 22, but there was a time lag of 13 months in the cycle 23, while, for the X2- and higher class ?ares, there was a time lag of 9 months in the cycle 21, but a one-month time advance existed in the cycle 22, and again a time lag of 32 months appeared in the cycle 23. 相似文献
18.
Neeraj Singh Bankoti Navin Chandra Joshi Bimal Pande Seema Pande Wahab Uddin Kavita Pandey 《New Astronomy》2011,16(4):269-275
This paper presents the study of normalized north–south asymmetry, cumulative normalized north–south asymmetry and cumulative difference indices of sunspot areas, solar active prominences (at total, low (?40°) and high (?50°) latitudes) and Hα solar flares from 1964 to 2008 spanning the solar cycles 20–23. Three different statistical methods are used to obtain the asymmetric behavior of different solar activity features. Hemispherical distribution of activity features shows the dominance of activities in northern hemisphere for solar cycle 20 and in southern hemisphere for solar cycles 21–23 excluding solar active prominences at high latitudes. Cumulative difference index of solar activity features in each solar cycle is observed at the maximum of the respective solar cycle suggesting a cyclic behavior of approximately one solar cycle length. Asymmetric behavior of all activity features except solar active prominences at high latitudes hints at the long term periodic trend of eight solar cycles. North–south asymmetries of SAP (H) express the specific behavior of solar activity at high solar latitudes and its behavior in long-time scale is distinctly opposite to those of other activity features. Our results show that in most cases the asymmetry is statistically highly significant meaning thereby that the asymmetries are real features in the N–S distribution of solar activity features. 相似文献
19.
Large-scale distribution of the sunspot activity of the Sun has been analyzed by using a technique worked out previously (Erofeev, 1997) to study long-lived, non-axisymmetric magnetic structures with different periods of rotation. Results of the analysis have been compared with those obtained by analyzing both the solar large-scale magnetic field and large-scale magnetic field simulated by means of the well-known flux transport equation using the sunspot groups as a sole source of new magnetic flux in the photosphere. A 21-year period (1964–1985) has been examined.The rotation spectra calculated for the total time interval of two 11-year cycles indicate that sunspot activity consists of a series of discrete components (modes) with different periods of rotation. The largest-scale component of the sunspot activity reveals modes with 27-day and 28-day periods of rotation situated, correspondingly, in the northern and southern hemispheres of the Sun, and two modes with rotation periods of about 29.7 days situated in both hemispheres. Such a modal structure of the sunspot activity agrees well with that of the large-scale solar magnetic field. Moreover, the magnetic field distribution simulated with the flux transport equation also reveals the same modal structure. However, such an agreement between the large-scale solar magnetic field and both the sunspot activity and simulated magnetic field is unstable in time; so, it is absent in the northern hemisphere of the Sun during solar cycle No. 20. Thus the sources of magnetic flux responsible for formation of the large-scale, rigidly rotating magnetic patterns appear to be closely connected, but are not identical with the discrete modes of the sunspot activity. 相似文献
20.
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