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1.
O. G. Badalyan 《Astronomy Reports》2011,55(10):928-942
The temporal variations observed in the monthly mean latitudes of sunspot groups are studied over 1874–2010 using the data
of the Greenwich Catalog and its NOAA-USEF extension. The 11-year cycle is quite clear in the temporal variations of the monthly
mean latitudes of sunspot groups (i.e., of the centers of spotting) in both the northern and southern hemispheres. The North-South
(N-S) asymmetry in the latitudes of sunspot groups defined as the difference between the absolute values of sunspot latitudes
observed in the N and S hemispheres is compared with the N-S asymmetry in the total area of sunspot groups determined on the
scales of 11 years and longer. The N-S asymmetry is interpreted as an imbalance in the hemispheres’ powers (asymmetry in the
total area of sunspot groups) and as spatial imbalance (asymmetry in the latitudes of the centers of spotting). This imbalance
is most clearly seen at the solar minima, i.e., in the gradual transition from one cycle to the other, when the absolute values
of the asymmetries observed both in the total sunspot area and in the sunspot latitudes reach their maxima. The results obtained
here can be helpful for analyses of the solar dynamo. 相似文献
2.
We apply Fourier and wavelet analyses to the precipitation and sunspot numbers in the time series (1901–2000) over Australia
(27°S, 133°E), Canada (60°N, 95°W), Ethiopia (8°N, 38°E), Greenland (72°N, 40°W), United Kingdom (54°N, 2°W), India (20°N,
77°E), Iceland (65°N, 18°W), Japan (36°N, 138°E), United States (38°N, 97°W), South Africa (29°S, 24°E) and Russia (60°N,
100°E). Correlation analyses were also performed to find any relation among precipitation, sunspot numbers, temperature, and
cloud-cover at the same spatial and temporal scale. Further correlations were also performed between precipitation with electron
and proton fluence at the time interval, 1987–2006. All these parameters were considered in annual and seasonal scales. Though
correlation study between precipitation and other parameters do not hint any linear relation, still the Fourier and wavelet
analyses give an idea of common periodicities. The 9–11 year periodicity of sunspot numbers calculated by Fourier transform
is also confirmed by wavelet transform in annual scale. Similarly, wavelet analysis for precipitation also supports the short
periods at 2–5 years which is verified by Fourier transform in discontinuous time over different geographic regions. 相似文献
3.
A multifaceted statistical study of all available data on solar activity during the Maunder minimum (1645–1715) is presented. The data include European telescope observations, Asian sunspot observations using the unaided eye, concentrations of cosmogeneous isotopes, and catalogues of polar aurorae. Joint analyses of data on the cosmogeneous isotopes 10Be and 14C are a promising source of information on solar activity in the past. The dates of relative sunspot maxima during the Maunder minimum are consistent with the idea that there were chaotic bursts of solar activity randomly distributed in time during this interval. The available evidence that the 11-year cyclicity was preserved in 1645–1715 are worthy of attention but require additional deep study and verification. No convincing evidence for a 22-year periodicity of the occurrence of sunspots during the Maunder minimum has been found. 相似文献
4.
Yong Wang Qi-Long Miao Chong-Yi E Jian-Kang Han Yuan-Yuan Ding 《Environmental Earth Sciences》2010,60(6):1257-1266
The δ18O data obtained from an 18.7 m ice core drilled in Chongce Ice Cap at an elevation of 6,530 m a.s.l. in the West Kunlun Mountains
on the northern Tibetan Plateau show a strong correlation with the summer temperature of the middle to upper troposphere over
the mid-high latitudes of Eurasia. Based on this, the δ18O record can be used as a proxy of the June–September mean temperature of the mid-upper troposphere (MUT) from 1903 to 1992.
The time span of the ice core record is much longer than the meteorological data available only after 1948. Using the empirical
mode decomposition method (EMD), the δ18O record is decomposed into various frequency components and compared with the solar irradiance variations of the same period.
The results show that (1) The June–September mean temperature of the MUT over Eurasian mid-high latitudes is completely decomposed
into four IMF (intrinsic mode function) components and an increasing trend. (2) Solar irradiance is decomposed into the Schwabe
cycle, the Hale cycle, the Gleissberg cycle, and an increasing trend. (3) The correlation coefficients between the June and
September mean temperatures of the MUT over Eurasian mid-high latitudes and solar irradiance on the longer timescales (at
least more than 11-year) show the significant correlations; their phase changes are basically identical in general, and (4)
the 11-year Schwabe cycle exists in the June–September mean temperature of the MUT over Eurasian mid-high latitudes during
most of the time from 1903 to 1992, and only in the two high-temperature phases (1929–1944 and from 1975 to the present) may
global warming disturb this relation. A full understanding of this phenomenon would shed insight into the potential consequence
of global warming on the MUT. 相似文献
5.
The spatial (latitude) distribution of sunspots is studied, including its dependence on solar activity. It is shown that the
latitude distributions of sunspots for a given year can be approximately described by the normal law, with its variance being
a linear function of the current level of solar activity. Thus, an increase in activity is accompanied by an expansion of
the zone of solar activity, in good agreement with earlier results. As the solar activity increases, the width of the zone
of sunspot generation and the latitude maximum of the sunspot density grow somewhat more slowly than the number of sunspots,
in agreement with observations. The results obtained can be used to reconstruct the spatial distributions of sunspots in the
past, interpret the magnetic activity of stars, and address the requirements of the dynamo theory in the form of constraints
imposed on models of cyclicity. 相似文献
6.
Surajit Chattopadhyay Deepak Jhajharia Goutami Chattopadhyay 《Comptes Rendus Geoscience》2011,343(7):433-442
In the present study, a prominent 11-year cycle, supported by the pattern of the autocorrelation function and measures of Euclidean distances, in the mean annual sunspot number time series has been observed by considering the sunspot series for the duration of 1749 to 2007. The trend in the yearly sunspot series, which is found to be non-normally distributed, is examined through the Mann-Kendall non-parametric test. A statistically significant increasing trend is observed in the sunspot series in annual duration. The results indicate that the performance of the autoregressive neural network-based model is much better than the autoregressive moving average and autoregressive integrated moving average-based models for the univariate forecast of the yearly mean sunspot numbers. 相似文献
7.
为探究太阳黑子活动与地区降雨量的关联性,采用连续小波变换方法,分析了1980年以来郑州地区(新郑站点)降雨量和太阳黑子数的数据变化,并对不同时段两者的相关性进行研究;进一步对两者进行交叉小波变换和小波相干谱分析,并根据两者关系通过太阳黑子数观测值对降雨量进行预测。结果表明：(1)不同时段降雨量和太阳黑子数的相关性存在正负差异的现象。降雨量的第一主周期尺度是21 a,在此主周期尺度下得到14 a主周期;太阳黑子数的第一主周期尺度是16 a,在此主周期尺度下得到11 a主周期(与经验值相符)。降雨量与太阳黑子数的主周期相差了3 a,因此导致两者的相关性在不同时段存在正负差异。(2)降雨量与太阳黑子数在1992—2008年的8～12 a时间尺度上关联性显著,且降雨量比太阳黑子数存在规律性的时间滞后,两者在2～4 a和7～10 a的时间尺度上关联性较好;降雨量比太阳黑子数分别在1991—2004年和2006—2013年这两个时间段上呈现规律性的滞后,两者在其他时间段的各时间尺度上关联性不明显。(3)根据延迟年数经验公式,由太阳黑子数观测值对降雨量进行预测,最近的降雨量峰年在2022年附近,与2... 相似文献
8.
Eruptions in the subglacial Katla caldera, South Iceland, release catastrophic jokulhlaups (meltwater floods). The ice surface
topography divides the caldera into three drainage sectors (Ko, So and En sectors) that drain onto Myrdalssandur, Solheimasandur
and Markarfljot plains, respectively. In historical times, floods from the Ko sector have been dominant, with only two recorded
So events. Geological records indicate that floods from the En sector occur every 500–800 years. A probabilistic model for
an eruption is formulated in general terms by a stochastic parameter that simulates a series giving the time interval in years
between two consecutive events. The model also contains a Markovian matrix that controls the location of the event and thereby
what watercourse is hit by the flood. A record of Katla eruptions since the 8th and the 9th century a.d., and geological information of volcanogenic floods towards the west over the last 8,000 years is used to calibrate the model.
The model is then used to find the probabilities for floods from the three sectors: Ko, So and En. The simulations predict
that the most probable eruption interval for the En sector and the So sector is several times smaller than the average time
interval, implying infrequent periods of high activity in these sectors. A correlation is found between the magnitude of eruptions
and the following time intervals. Using the statistical approach and considering this magnitude–time interval correlation,
the probability of an eruption in Katla volcano is considered to be 20% within the next 10 years. This compares to a probability
of 93% if only a simple average is considered. These probabilities do not take account of long-term eruption precursors and
should therefore be regarded as minimum values. 相似文献
9.
Results of the isotope-geochronological studies of the Late Cenozoic magmatism of Caucasus have been considered. The Neogene-Quaternary
volcanic activity is found to have evolved during the last 15 m. y. being most intensive in the Middle-Late Pliocene. Within
separate neovolcanic areas of the Caucasus region, magmatism was of a clearly discrete character when intense eruption periods
interchanged with prolonged (up to several million years) times of quiet conditions. Four stages of young magmatism of the
Caucasus are recognized: the Middle Miocene (15–13 Ma), the Late Miocene (9–5 Ma), the Pliocene (4.5–1.6 Ma), and the Quaternary
(less than 1.5 Ma). However, for certain areas the time limits of these stages were shifted relative to each other and overlap
the whole age range from the mid-Miocene to the end of the Quaternary period. Therefore, within the collision zone, the Neogene-Quaternary
magmatism evolved almost continuously during almost the last 9 m. y., but in the time interval of 13–9 Ma in the Caucasian
segment, volcanic activity was possibly low. No evidence of directed lateral migration of volcanic activity within the entire
Caucasus region was found. At the same time, in the Lesser Caucasus the young magmatism commenced earlier (∼15 Ma), compared
to the Greater Caucasus (∼8 Ma). 相似文献
10.
The anomalies of summer rainfall (June–August) for the last 500 years in China have been estimated according to the relationship
between the instrumentally observed rainfall and the degrees of floods and droughts for the last 25 years. It is shown that
calculated anomalies of average rainfall for 10, 20 and 30 year periods have sufficient accuracies. The long-term climatic
variations for the last 500 years are discussed based on the estimated anomalies of summer rainfall of 25 stations over the
E part of China for the last 500 years. For example, there were prolonged drought in the N of China at about the end of Ming
dynasty, but there were extensive floods in China for the early times of Qing dynasty. The anomalies of rainfall for the last
500 years were averaged along latitude zone and their decade running mean were formed. It was found that the long-term variations
are very clear. The 80 year cycle is predominating. Besides, an about 200 year cycle is also shown in the charts of 50-year
mean rainfall anomalies. It is indicated that both above mentioned cycles relate closely to the solar activity. 相似文献
11.
D. S. V. V. D. Prasad P. V. S. Rama Rao G. Uma S. Gopi Krishna K. Venkateswarlu 《Journal of Earth System Science》2005,114(4):437-441
Using the data of amplitude scintillations recorded at 244 MHz from the geostationary satellite, FLEETSAT (73‡E) at a low
latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip), during the increasing sunspot activity period of 1997–2000, the effect
of the geomagnetic storms on the occurrence of ionospheric scintillations has been studied. A total of 60 SC storms studied
during this period, following the Aarons’ criterion, reveals that the local time of onset of the recovery phase of the geomagnetic
storms play an important role in the generation or inhibition of the ionospheric irregularities. Out of the 60 storms studied,
nearly 60 to 70% satisfied the categories I, II and III of Aarons’ criteria. However, in the remaining 30 to 40% of the cases,
no consistent results were observed. Thus, there is a necessity for further investigation of the effect of geomagnetic storms
on ionospheric irregularities, particularly with reference to the altitude variations of the F-layer (h’F) relating to the
changes in the local electric fields. 相似文献
12.
Shimaraev M. N. Troitskaya E. S. Blinov V. V. Ivanov V. G. Gnatovskii R. Yu. 《Doklady Earth Sciences》2012,442(2):272-276
Based on shipboard and satellite observations, the characteristics of upwelling in Lake Baikal in the period of direct temperature
stratification have been determined for the first time. Coastal upwellings appear annually under the effect of run-down and
alongshore winds and are traced along the coast to a distance of up to 60–100 km and up to 250 km in North Baikal. Analogous
to the way it occurs in seas, water rises from the depths of 100–200 m (350 m as a maximum) at the velocity of 0.1 × 10−2−6.5 × 10−2 cm/s. Divergence in the field of intràbasin cyclonic macrovortices produces upwelling in the Baikal pelagic zone and downwelling
in the vicinity of shores; this lasts from 7 to 88 days and covers the depth interval of 80–300 m in August and up to 400–800
m in early-mid November. The area of upwellings occupies up to 20–60% of the separate basins of the lake. Vertical circulation
of water in the field of pelagic upwellings leads to intensification of coastal currents and to formation of the thermobar
with a heat inert zone in the central part of the lake in November, and this thermobar is not observed in other lakes, at
that. 相似文献
13.
The sector structure and variations in the large-scale magnetic field of the Sun are studied in detail using solar magnetic-field data taken over a long time interval (1915–1990). The two-sector and four-sector structures are independent entities (i.e., their cross correlation is very small), and they are manifest in different ways during the main phases of the 11-year cycle. The contribution of the two-sector structure increases toward the cycle minimum, whereas that of the four-sector structure is larger near the maximum. The magnetic-field sources determining the two-sector structure are localized near the bottom of the convection zone. The well-known 2–3-year quasi-periodic oscillations are primarily associated with the four-sector structure. The variations in the rotational characteristics of these structures have a period of 55–60 years. The results obtained are compared with the latest helioseismology data. 相似文献
14.
Prediction of sunspot cycle is a vital activity in space mission planning and various engineering decision making. In the present study, the sunspot cycle prediction has been carried out by a hybrid model which employs multivariate regression technique and the binary mixture of Laplace distribution (BMLD) function. The Expectation Maximization (EM) algorithm is being applied to the multivariate regression analysis to obtain a robust prediction of the sunspot cycle. Sunspot cycle 24 has been predicted using this technique. Multivariate regression model has been derived based on the available cycles 1 to 23. This model could predict cycle 24 as an average of previous cycles. Prediction from this model has been refined to capture the cycle characteristics such as bimodal peak at the high solar activity period by incorporating a predicted peak sunspot number from the BMLD model. This revised prediction has shown more accuracy in forecasting the major discrete features of sunspot cycle like maximum amplitude, the Gnevyshev gap, time duration from peak to peak amplitude, and the epoch of peak amplitude. This refined prediction shows that cycle 24 will be having a peak amplitude of 78 with an uncertainty of ±25. Moreover, the present forecast says that, cycle 24 will be having double peak with a strong second peak compared to the first peak. This hypothesis is found to be true with the realized data of cycle 24. Further, this techniques have been validated by predicting sunspot cycles 22 and 23. A preliminary level prediction of sunspot cycle 25 also been carried out using the technique presented here. Present study predicts that, cycle 25 also will be a modest cycle like the present cycle 24, and the peak amplitude may vary in a band of 75–95. 相似文献
15.
The latitude-time distribution of sunspot groups violating Hale polarity rule is considered for 1988–2004. This distribution exhibits a cyclic behavior similar to the general 11-year sunspot-activity cycle. The relative number of violating groups is used to estimate the ratio of the fluctuating and regular components of the toroidal magnetic field at the base of the convection zone. 相似文献
16.
A numerical investigation of the desaturation process at the argillaceous Tournemire site has been carried out. This desaturation
is initialized by the contact of the saturated rock with the ambient air in excavated openings. The used hydraulical model
is based on the Richards’ approximation for unsaturated one phase flow coupled with the deformation of a porous medium with
anisotropic linearly elastic behavior. In relation to the extent of the desaturated zone around an excavated opening, the
intrinsic permeability and the relative permeability have been identified to be the most important model parameters. The mechanical
deformation process itself, the seasonal influences and the tunnel lining are less important for the formation of the desaturated
zone. The comparison with measured saturation values bares some difficulties but indicates the principle capacity of the applied
finite element codes to simulate the desaturation process. The consideration of seasonal changes in humidity in the ambient
air results in a constantly recurring desaturation–resaturation cycle in the near field of the openings. This seasonally influenced
zone amount 1–2 m and is nearly independent from time and from a variation of model parameters within a reasonable range.
The possibility of material weakening in this zone is of special interest, since claystone is a potential host rock for the
disposal of radioactive waste. 相似文献
17.
A catalog of maser spectra in the 1.35-cm water-vapor line towards the maser source NGC 2071 in a region of massive star formation
is presented for 1994–2010. The observations were carried out using the 22-m antenna of the Pushchino Radio Astronomy Observatory
with a spectral resolution of 0.101 km/s (0.0822 km/s after the end of 2005). Based on the data throughout the monitoring
since 1980, two very different cycles of maser activity were found. The first (1980–1992) is characterized by high activity
within a broad range of radial velocities. Emission at velocities near 7 km/s predominated in 1980–1986, and emission near
14–16 km/s, in 1987–1992. In 1997–2008, the maser intensity was appreciably lower than in the first activity cycle. Numerous
flares of individual emission features were observed. Identifications based on VLA data show that strong flares took place
in both maser sources, IRS1 and IRS3. Both sources demonstrated a low level of maser activity during essentially the same
epochs (1977, 1995–1997, and the close of 2009 through the beginning of 2010), although the sources are separated by at least
2000 AU. 相似文献
18.
Yu. A. Nagovitsyn V. G. Ivanov E. V. Miletsky E. Yu. Nagovitsyna 《Astronomy Reports》2010,54(5):476-480
An approach to reconstructing solar activity in the past is used to study its time evolution. It is already possible to reconstruct
not only the general level of solar activity on long timescales, but also particular aspects of its development: sunspot dominance
in either hemisphere, the drift and latitude spread of the sunspot-formation zone, and features in the spatial distribution
of the activity at specific epochs, such as the Maunder minimum. 相似文献
19.
M. G. Ogurtsov 《Astronomy Reports》2005,49(6):495-499
Decade-averaged Wolf numbers are reconstructed for the time interval 8005 B.C.–1945 A.D. using radiocarbon data derived from tree rings. Comparisons of other paleoastrophysical reconstructions of solar activity with this temporal series verify its validity and reliability. A prediction of the mean solar activity for the next forty years is made using these reconstructed Wolf numbers. It is likely that the mean solar activity during 2005–2045 will be lower than the activity of recent decades. This conclusion is compared with the long-term predictions proposed by other researchers. The prospects for paleoastrophysical predictions for the long-term variations of solar activity in the future are discussed. 相似文献
20.
Guido Schreurs Jörg Giese Alfons Berger Edwin Gnos 《International Journal of Earth Sciences》2010,99(8):1827-1847
The Ranotsara shear zone in Madagascar has been considered in previous studies to be a >350-km-long, intracrustal strike-slip
shear zone of Precambrian/Cambrian age. Because of its oblique strike to the east and west coast of Madagascar, the Ranotsara
shear zone has been correlated with shear zones in southern India and eastern Africa in Gondwana reconstructions. Our assessment
using remote sensing data and field-based investigations, however, reveals that what previously has been interpreted as the
Ranotsara shear zone is in fact a composite structure with a ductile deflection zone confined to its central segment and prominent
NW–SE trending brittle faulting along most of its length. We therefore prefer the more neutral term “Ranotsara Zone”. Lithologies,
tectonic foliations, and axial trace trajectories of major folds can be followed from south to north across most of the Ranotsara
Zone and show only a marked deflection along its central segment. The ductile deflection zone is interpreted as a result of
E–W indentation of the Antananarivo Block into the less rigid, predominantly metasedimentary rocks of the Southwestern Madagascar
Block during a late phase of the Neoproterozoic/Cambrian East African Orogeny (c. 550–520 Ma). The Ranotsara Zone shows significant
NW–SE striking brittle faulting that reactivates part of the NW–SE striking ductile structures in the flexure zone, but also
extends along strike toward the NW and toward the SE. Brittle reactivation of ductile structures along the central segment
of the Ranotsara Zone, confirmed by apatite-fission track results, may have led to the formation of a shallow Neogene basin
underlying the Ranotsara plain. The present-day drainage pattern suggests on-going normal fault activity along the central
segment. The Ranotsara Zone is not a megascale intracrustal strike-slip shear zone that crosscuts the entire basement of southern
Madagascar. It can therefore not be used as a piercing point in Gondwana reconstructions. 相似文献