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1.
A series of yearly data on the concentration of radioactive carbon 14C in tree rings measured at the Tbilisi State University in 1983–1986 and covering the time interval 1600–1940 is statistically analyzed. We find evidence for a 22-year cyclicity in the intensity of Galactic cosmic rays (GCRs) during the Maunder minimum of the solar activity (1645–1715), testifying that the solar dynamo mechanism continued to operate during this epoch. Variations of Δ14C on timescales of tens and hundreds of years correlate well with the corresponding variations of the GCR intensity and solar activity, making radiocarbon a reliable source of information on long-timescale variations of solar activity in the past. Short-timescale (<30 years) fluctuations of Δ14C may be appreciably distorted by time variations not associated directly with solar activity; probable origins of this distortion are discussed. 相似文献
2.
A new series of yearly-mean relative sunspot numbers SN 2 that has been extrapolated into the past (to 1610) is presented. The Kislovodsk series with the scale factor b = 1.0094 ± 0.0059 represents a reasonable continuation of the mean-monthly and mean-yearly total sunspot areas of the Greenwich series after 1976. The second maximum of the 24th solar-activity cycle was not anomalously low, and was no lower than 6 of the past 13 cycles. A series A 2 of values for the total sunspot area in 1610–2015 has been constructed, and is complementary to new versions of the series of the relative number of sunspots SN 2 and the number of sunspot groups GN 2. When needed, this series can be reduced to yield a quantity having a clear physical meaning—the spot absolute magnetic flux Φ Σ(t)[Mx] = 2.16 × 1019 A(t) [mvh]. The maximum sunspot area during the Maunder minimum is much higher in the new series compared to the previous version. This at least partially supports the validity of arguments that cast doubt on the anomalously low ampltude of the solar cycles during the Maunder minimum that has been assumed by many researchers earlier. 相似文献
3.
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
4.
Changes in solar constant over an 11 yr cycle suggest a certain, but limited, degree of solar forcing of climate. The high-resolution climate (oxygen isotope) record of the Greenland GISP2 (Greenland Ice Sheet Project 2) ice core has been analyzed for solar (and volcanic) influences. The atmospheric14C record is used as a proxy of solar change and compared to the oxygen isotope profile in the GISP2 ice core. An annual oxygen isotope profile is derived from centimeter-scale isotope measurements available for the post-A.D. 818 interval. Associated extreme summer and winter isotope ratios were found to yield similar climate information over the last millennium. The detailed record of volcanic aerosols, converted to optical depth and volcanic explosivity change, was also compared to the isotope record and the oxygen isotope response calibrated to short-term volcanic influences on climate. This calibration shows that century-scale volcanic modulation of the GISP2 oxygen isotope record can be neglected in our analysis of solar forcing. The timing, estimated order of temperature change, and phase lag of several maxima in14C and minima in18O are suggestive of a solar component to the forcing of Greenland climate over the current millennium. The fractional climate response of the cold interval associated with the Maunder sunspot minimum (and14C maximum), as well as the Medieval Warm Period and Little Ice Age temperature trend of the past millennium, are compatible with solar climate forcing, with an order of magnitude of solar constant change of 0.3%. Even though solar forcing of climate for the current millennium is a reasonable hypothesis, for the rest of the Holocene the century-scale events are more frequent in the oxygen isotope record than in the14C record and a significant correlation is absent. For this interval, oceanic/atmospheric circulation forcing of climate may dominate. Solar forcing during the surprisingly strong 1470 yr climate cycle of the 11,000–75,000 yr B.P. interval is rather hypothetical. 相似文献
5.
Magnetic Hα synoptic maps of the Sun for 1915–1999 are analyzed and the intensities of spherical harmonics of the large-scale solar magnetic field computed. The possibility of using these Hα maps as a database for investigations of long-term variations of solar activity is demonstrated. As an example, the magnetic-field polarity distribution for the Hα maps and the analogous polarity distribution for the magnetographic maps of the Stanford observatory for 1975–1999 are compared. An activity index A(t) is introduced for the large-scale magnetic field, which is the sum of the magnetic-moment intensities for the dipole and octupole components. The 11-year cycle of the large-scale solar magnetic field leads the 11-year sunspot cycle by, on average, 5.5 years. It is concluded that the observed weak large-scale solar magnetic field is not the product of the decay of strong active-region fields. Based on the new data, the level of the current (23rd) solar-activity cycle and some aspects of solar-cycle theory are discussed. 相似文献
6.
《Quaternary Science Reviews》2007,26(1-2):82-97
Identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors—solar forcing. Prior to the period of direct solar observations, radionuclide abundances in natural archives provide the best-known proxies for changes in solar activity. Here we present two independent reconstructions of changes in solar activity during the last 1000 yr, which are inferred from 10Be and 14C records. We analyse the tree-ring 14C data (SHCal, IntCal04 from 1000 to 1510 AD and annual data from 1511 to 1950 AD) and four 10Be records from Greenland ice cores (Camp Century, GRIP, Milcent and Dye3) together with two 10Be records from Antarctic ice cores (Dome Concordia and South Pole). In general, the 10Be and 14C records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates. Differences between 10Be records from Antarctica and Greenland indicate that climatic changes have influenced the deposition of 10Be during some periods of the last 1000 yr. The radionuclide-based reconstructions of past changes in solar activity do not always agree with the sunspot record, which indicates that the coupling between those proxies is not as close as has been sometimes assumed. The tree-ring 14C record and 10Be from Antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr. 相似文献
7.
Meloth Thamban C. M. Laluraj Sushant S. Naik Arun Chaturvedi 《Journal of the Geological Society of India》2011,78(1):19-29
Antarctic ice core records have provided unprecedented information on past climatic changes and forcing factors on decadal
to millennial timescales. The glaciochemical and stable isotope records of a shallow ice core from the coastal Dronning Maud
Land (East Antarctica) were used here to reconstruct the coastal Antarctic environmental variability during the past ∼470
years. Sea salt ion data indicate a significant additional contribution of chloride ions compared to sea water values, possibly
through atmospheric scavenging. The nitrate (NO3
−) profile exhibit significant temporal shifts than that of the sulphate (SO4
2−), with a major shift around 1750 AD. The changes in NO3
− record are synchronous with the proxy record of solar activity (10Be profile from a South Pole ice core), suggesting enhanced NO3
− values during periods of reduced solar activity like the Dalton Minimum (∼1790–1830 AD) and Maunder Minimum (∼1640–1710 AD).
The δ18O records reveal that the more negative δ18O values were coeval with several events of increased NO3
− concentrations, suggesting enhanced preservation of NO3
− during periods of reduced air temperatures. The δ18O and δD records of the core also suggest significant short-term and long-tem variability with more negative values indicating
relatively lower air temperatures prior to 1715 AD. The δ18O records also revealed a significant warming of 2.7°C for the past 470 years, with a warming of ∼0.6°C per century. 相似文献
8.
Variability of strontium and carbon isotopes are reported from a speleothem from Central Florida, USA. Thermal ionization mass spectrometry of uranium–thorium isotopes indicate the speleothem was precipitated during the last 4000 years. Sr concentrations are negatively correlated with δ13C, a relationship inferred to record changes in soil productivity. Coeval changes in the Sr content and δ13C signals, as induced by soil productivity, are explained by changing precipitation above the cave. Both proxies record a 170–180-year solar cycle that has also been found in the Gulf of Mexico marine records and elsewhere. Consequently, this result provides evidence of an extraterrestrially driven modulator of precipitation in Central Florida. 相似文献
9.
RATAN-600 observations of a microwave source located above the active region NOAA 10105 obtained on September 7–20, 2002 with a frequency resolution of ~10% have revealed a spectral feature near 3.04 cm that can be interpreted as a neutral hydrogen line. This feature was observed September 11, 2002, in both absorption and emission, and was detected in the spectra of various portions of the source (sunspot, flocculus, and background). The maximum line depth of (35 ± 5)% of the source brightness was observed at the start of the observations (9.2h UT) in the flocculus in absorption. The line intensity decreased rapidly with time, becoming less than the measurement errors by 9.7h UT. It is most likely that the 3.04 cm emission is related to a 2B chromospheric flare (M2.2 X-ray burst) observed at ~7.5h UT in the floccular field, near the main sunspot of NOAA 10105. In this case, the total duration of the event was about two hours. These observations are consistent with earlier statistical studies, and refines these based on data with higher spatial resolution. Recommendations for further observational studies of the solar 3.04-cm hydrogen line are presented; requirements for theories of the 3.04 cm line taking into account nonequilibrium states of the active-region plasma are indicated. 相似文献
10.
Occultation observations of the intensity of the FeXIV 530.3 nm and FeX 637.4 nm forbidden lines detected at the Kislovodsk Mountain Station during 1957–2002, indicate long-term changes in the structure of the solar corona. The monthly average intensities of green (KI530.3) and red (KI637.4) spectral lines are calculated for all latitudes (0°–90°) and for a high-latitude zone (45°–90°). A strong correlation (r = 0.91) between the green KI530.3 line intensity and the Wolf numbers is found and used to fill gaps in the observations. The ratio KI637.4/KI530.3 takes on its maximum value at the solar minimum. The KI 637.4 p /KI 530.3 p ratio in the high-latitude solar zone (45°–90°) increased by more than a factor of two during 1957–2002. This means that the fraction of cool regions in the polar corona has more than doubled over these years. We suggest that this increase in the number of cool regions is related to an increase in the area of the polar solar zones occupied by magnetic field of a single polarity at the solar minimum, and possibly to an increase in the area occupied by polar coronal holes. This is associated with long-term variations in the internal structure of the Sun. 相似文献
11.
This study reveals the changes and evolution of rainstorm-driven intermediate floods occurring and driving multiple damaging hydrological events in the Rhone River Basin (RRB), since 1500 until 2010. A parsimonious approach was developed to simulate the major hydroclimatological flood-producing forcing, the Multiscale Rainstorm Climate Model (STORMCLIMM). We collected the frequency of intermediate floods—a type of particularly hazardous floods commonly taking place between June and beginning of November—from the RCB to be compared to STORMCLIMM estimates. The latter, smoothed by a moving window of 21 years, results in a high-pass filter in the time domain, which magnifies the signal of forcing variations causing intermediate floods. The RRB showed large temporal variations in both extreme rainstorms and associated multidecadal intermediate-floods (MUDIF) frequency at different climatic periods and land-use systems through historical times. An important peak was observed in the Maunder Minimum (1645–1715 AD). The model allowed detecting MUDIF occurred in the historical times. The situation becomes interesting with respect to recent times, because the Rhone landscape looks more vulnerable in the last decades as a consequence of land-use changes and climate shift towards more erratic and intensive storms. This evidence suggests that the interactions of land-use and climatic changes may turn into considerable vulnerability to fluvial flooding and agro-ecosystem connected to them for upcoming years. The Rhone, for example, provides basis for use of hydrological indicators (such as the one represented by STORMCLIMM) for one site or region and which, through minor modifications, can be made relevant to specific needs. 相似文献
12.
M. A. Zel’dovich Yu. I. Logachev G. M. Surova K. Kecskemety I. S. Veselovskii 《Astronomy Reports》2016,60(7):687-693
The energy spectra and relative abundances of 3He, 4He, C, O, and Fe ions with energies of ~0.04–2 MeV/nucleon are studied using data from the ULEIS instrument on board the ACE spacecraft obtained during quiescent periods in 2006–2012. During the unique, prolonged minimum between cycles 23 and 24, 35 quiescent periods were distnguished, during which solar-wind flows from near-equatorial coronal holes (CHs) were detected. It is shown that the C/O and Fe/O ratios for suprathermal ions correspond to the relative abundances of the corresponding thermal ions in the fast and slow (Maxwellian) solar wind (SWICS/ACE), while the 4He/O ratio exceeds the corresponding ratio in the solar wind by a factor of two. The intensities of the 3He, 4He, C, O, and Fe suprathermal ions in outflows from CHs grow with the speed of the solar wind. This indicates that, in periods ofminimumsolar activity, suprathermal ions from CHs represent a high-temperature “tail” of the solar wind. An additional flux of suprathermal helium ions may also be contributed by other external sources. 相似文献
13.
The large-scale stream structure of the solar wind near the Sun and its evolution during the 11-year solar activity cycle are investigated. The study is based on observations of scattering of the radiation from compact natural radio sources at radial distances R≤14R S (R S is the solar radius). Regular observations were conducted in 1981–1998 on the RT-22 and DKR-1000 radio telescopes of the Russian Academy of Sciences at Pushchino, at λ=1.35 cm and 2.7 m, respectively. The radial dependences of the interplanetary scintillations m(R) and the scattering angle 2?(R) are considered together with the structure of large-scale magnetic fields in the solar corona at R=2.5R S. The entire range of variations in the level of scattering and the associated heliolatitude flow structures in the subsonic solar wind forms over the 11-year solar cycle, as a direct result of the large-scale structure of the evolving magnetic fields at the source of the solar-wind streamlines. 相似文献
14.
J.D. Gilmour 《Geochimica et cosmochimica acta》2010,74(1):380-6266
Models capable of explaining the differences between the isotopic compositions of the planetary noble gas components “Q” and “P3” (widespread in primitive meteorites) and average solar system material as sampled by the solar wind are presented, and their implications discussed.Small, variable amounts of known presolar components and 129Xe from 129I decay are present in Q gases alongside a solar composition that has been mass fractionated. These most likely arise either from mixing during parent body processing or co-release from poorly retentive phases during analysis. Thus the heavy noble gas budget of primitive meteorites is dominated by a component derived from material with the average composition of the solar system.In contrast, P3 seems best explained as a presolar component, consistent with isolation from bulk material that subsequently evolved to the solar composition as newly synthesised material was added. Examination of Kr-P3 identifies the addition as having had the signature of the weak s-process, and demonstrates that a second process that contributes the isotopes of krypton not produced in the s-process (residual isotopes) must also have added material to the reservoir as it evolved to the solar composition. Total s-process contributions required of 132Xe and 84Kr are at least ∼1% of the present budget, as is that of the residual krypton “component”.While concentrations of P3 vary with extents of parent body processing, concentrations of 129Xe excess from 129I decay associated with P3 are roughly constant in those least processed meteorites that retain a P3 signature (apart from ALH77307). This has a natural explanation in the different chemical behaviours of iodine and xenon if 129I was alive in P3 in the early solar system. The presence of live 129I in P3 in the early solar system imposes a loose constraint that the P3 component was isolated from a parent reservoir less than ∼100 Myr before the formation of the solar system.The model of evolution from P3 gases to the solar composition requires that residual krypton isotopes are not products of a conventional r-process that also synthesises 129I. Separate sites for synthesis of residual isotopes of krypton and the heavy element r-process are consistent with observations of metal poor stars, but do not correspond to the two r-processes invoked to account for variations between the 182Hf and 129I systems. Since the weak s-process is implicated as the source of the s-process material contributed as the P3 reservoir evolved to a solar composition, the massive stars that host it may also host the process that synthesises residual krypton isotopes. The recent presence of nearby massive stars is consistent with an emerging picture of the environment of solar system formation. 相似文献
15.
The shift between the solar activity cycles in the northern and southern hemispheres of the Sun is studied using data on sunspot number and area. The data obtained are compared with archival information on episodes of appreciable solar-cycle asymmetry. The small phase shift between recent activity cycles in the northern and southern solar hemispheres differs considerably from the shift for episodes of appreciable deviations from dipolar symmetry in the sunspot distribution detected with various degrees of confidence in archival astronomical data from the 17th–19th centuries. The current time shift between the hemispheres is insignificant, about 6–7 months. This shift has changed its sign twice in recent solar history; this probably corresponds to more or less periodic variations with a timescale close to the duration of the Gleissberg cycle. 相似文献
16.
Manuela A. Fehr Mark Rehkämper Alex N. Halliday Uwe Wiechert Detlef Günther Jennifer L. Eigenbrode Douglas Rumble III 《Geochimica et cosmochimica acta》2005,69(21):5099-5112
New precise Te isotope data acquired by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) are presented for selected extraterrestrial and terrestrial materials. Bulk samples of carbonaceous, ordinary and enstatite chondrites as well as the metal and sulfide phases of iron meteorites were analyzed to search for nucleosynthetic isotope anomalies and to find evidence of formerly live 126Sn, which decays to 126Te with a half-life of 234,500 yr. None of the meteorites show evidence of mass dependent Te isotope fractionations larger than 2‰ for δ126/128Te. Following internal normalization of the data to 125Te/128Te, the Te isotope ratios of all analyzed meteorites were found to be identical to a terrestrial standard, within uncertainties. This provides evidence that the regions of the solar disk that were sampled during accretion of the meteorite parent bodies were well mixed and homogeneous on a large scale, with respect to Te isotopes. The data acquired for bulk carbonaceous chondrites indicate that the initial 126Sn/118Sn ratio of the solar system was <4 × 10−5, but this is dependent on the assumption that no redistribution of Sn and Te occurred since the start of the solar system. Five Archean sedimentary sulfides that display both mass dependent and mass-independent isotope effects for S yield internally normalized Te isotope data, which indicate that mass-independent Te isotope effects are absent. The mass dependent fractionations in these samples are constrained to be less than ∼1‰ for δ126/128Te. 相似文献
17.
18.
Climatic periodicities recorded in lake sediment magnetic susceptibility data: Further evidence for solar forcing on Indian summer monsoon 总被引:1,自引:0,他引:1
The Indian summer monsoon exhibits considerable spatio-temporal variability.It is therefore important to understand its dynamics and the inherent periodicities.In this study,we have performed spectral and wavelet analyses of magnetic susceptibility data for sediments from Thimmannanayakanakere(TK)-a small lake in southern India.The main objective of this investigation is to identify and explain the possible origin of the prominent periodicities present in the magnetic susceptibility data.Significant periodicities in the TK χ_(lf)data are centered at 906,232,147,128,96,61,54 and 44 years,which might have a solar origin.The wavelet power spectrum of the raw and detrended χ_(lf)data confirms the findings of spectral analysis and also provides temporal variations of the significant cyclicities during the past3700 cal.years B.P.Positive correlation is documented between sunspot activity and TK xif data;crossspectral analysis of the reconstructed sunspot data and TK xif data suggest that there is a strong coherence between the two datasets as significant periodicities are documented in both.There is a good match between the TK xif and the reconstructed total solar irradiance data for the past 1200 years.However,an out-of-phase relationship is documented at certain time-intervals,which may be attributed to uncertainties in the age-depth model.The results obtained from this study show that solar variations are the main controlling factor of the southwest monsoon and,like other archives from different regions in India,the TK lake sediments have also recorded these solar signatures. 相似文献
19.
A. N. Rostopchina V. P. Grinin D. N. Shakhovskoi P. S. Thé N. Kh. Minikulov 《Astronomy Reports》2000,44(6):365-375
We present the results of simultaneous UBVRI photometric and polarimetric observations of the Ae Herbig star SV Cep made in 1987–1998. Over these 11 years, only a single deep (ΔV>1m) brightness minimum was observed. Near this minimum, the brightness decrease was accompanied by an increase of the linear polarization, as is typical of young UX Ori stars. The photometric observations of SV Cep indicate reversals of the color tracks in brightness minima, as is common for stars of this type, as well as variations of the slopes of the color tracks during and after minima. This provides evidence that the circumstellar dust clouds screening the star differ in their sizes and masses, and also in the optical properties of their dust particles. A Fourier analysis of the brightness variations of SV Cep (including data from the literature) confirms the presence of previously suspected activity cycles with periods P 1=4000d and P 2=670d The polarimetric observations indicate that, along with the inverse correlation between the degree of linear polarization and brightness, the polarization parameters vary on characteristic time scales of 4000 and 1000 days. This suggests the existence of large-scale inhomogeneities in the circumstellar dust disk rotating about the star. 相似文献