An early estimate for the size of cycle 23   总被引：1，自引：0，他引：1  

Robert M. Wilson 《Solar physics》1992,140(1):181-193

Two features are found in the modern era sunspot record (cycles 10–22: ca. 1850-present) that may prove useful for gauging the size of cycle 23, the next sunspot cycle, several years ahead of its actual onset. These features include an inferred long-term increase against time of maximum amplitude (RM, the maximum value of smoothed sunspot number for a cycle) and the apparently inherent differing natures of even- and odd-numbered sunspot cycles, especially when grouped consecutively as even-odd cycle pairs. Concerning the first feature, one finds that 6 out of the last 6 sunspot cycles have had RM 110.6 (the median value for the modern era record) and that 4 out of 6 have had RM > 150. Presuming this trend to continue, one anticipates that cycle 23 will likewise have RM 110.6 and, perhaps, RM > 150. Concerning the second feature, one finds that, when one groups sunspot cycles into consecutively paired even-odd cycles, the odd-following cycle has always been the larger cycle, 6 out of 6 times. Because cycle 22 had RM = 158.5, one anticipates that cycle 23 will have RM > 158.5. Additionally, because the average difference between RM(odd) and RM(even) for consecutively paired even-odd cycles is 40.3 units (sd = 14.2), one expects cycle 23 to have RM 162.3 (RM = 198.8 ± 36.5 at the 95% level of confidence). Further, because of the rather strong linear correlation (r = 0,959, se = 13.5) found between RM(odd) and RM(even) for consecutively paired even-odd cycles, one infers that cycle 23 should have RM 176.4 (RM = 213.9 ± 37.5 at the 95% level of confidence). Since large values of RM tend to be associated with fast rising cycles of short ascent duration and high levels of 10.7-cm solar radio flux, cycle 23 is envisioned to be potentially one of the greatest cycles of the modern era, if not the greatest.  相似文献   

Textures in a poikilitic olivine gabbro cumulate: Evidence for supercooling     

C. Tegner  J. R. Wilson 《Mineralogy and Petrology》1995,54(3-4):161-173

Summary Supercooling of repeated influxes of high-MgO ( 13.5 wt% MgO) tholeiitic magma emplaced along the floor of the Kap Edvard Holm magma chamber led to the formation of fine grained, intraplutonic quench zones that define the bases of 12 macrorhythmic units. The quench zones grade upwards into poikilitic cumulates containing olivine dendrites, suggesting supercooling by 40°C. Supercooling led to early, precumulus crystallization of metastable, non-equilibrium plagioclase, followed by co-precipitation of cumulus plagioclase and olivine. Later nucleation of clinopyroxene followed by rapid growth led to crystallization of zoned oikocrysts during the cumulus stage, followed by postcumulus overgrowth and crystallization of discrete intercumulus grains. At least four generations of plagioclase crystals appear to be preserved.

---

Gefüge in einem poikilitischen Olivingabbro-Kumulat: Hinweis auf Unterkühlung

Zusammenfassung Unterkühlung von mehrmals nachströmendem MgO-reichen (ca. 13,5 Gew.% MgO), tholeiitischen Magma, das sich am Boden der Magmenkammer vom Kap Edvard Holm sammelte, führte zur Bildung von feinkbrnigen Zonen mit Abschreckungsgefüge, die jeweils die Basis von 12 makrorhythmischen Einheiten bilden. Diese Zonen gehen im Hangenden in poikilitische Kumulate über, die Olivin-Dendriten enthalten, was auf eine Unterkühlung um ca. 40°C hindeutet. Die Unterkühlung führte zu einer frühen präkumulativen Kristallisation von metastabilem, nicht im Gleichgewicht befindlichem Plagioklas, gefolgt von gleichzeitiger Präzipitation von Kumulus-Plagioklas und -Olivin. Eine spätere Keimbildung von Klinopyroxen, die von raschem Wachstum abgelöst wurde, führte während der Akkumulation zur Kristallisation von zonierten Oikokrysten. Danach folgte eine postkumulative Überwachsung und die Kristallisation von Einzelkörnern in den Zwischenräumen. Zumindest vier Generationen von Plagioklaskristallen scheinen erhalten zu sein.

---

---

With 5 Figures  相似文献   

On the use of ‘first spotless day’ as a predictor for sunspot minimum     

Robert M. Wilson 《Solar physics》1995,158(1):197-204

Defining the first spotless day of a sunspot cycle as the first day without spots relative to sunspot maximum during the decline of the solar cycle, one finds that the timing of that occurrence can be used as a predictor for the occurrence of solar minimum of the following cycle. For cycle 22, the first spotless day occurred in April 1994, based on the International sunspot number index, although other indices (Boulder and American) indicated the first spotless day to have occurred earlier (September 1993). For cycles 9–14, sunspot minimum followed the first spotless day by about 72 months, having a range of 62–82 months; for cycles 15–21, sunspot minimum followed the first spotless day by about 35 months, having a range of 27–40 months. Similarly, the timing of first spotless day relative to sunspot minimum and maximum for the same cycle reveals that it followed minimum (maximum) by about 69 (18) months during cycles 9–14 and by about 90 (44) months during cycles 15–21. Accepting April 1994 as the month of first spotless day occurrence for cycle 22, one finds that it occurred 91 months into the cycle and 57 months following sunspot maximum. Such values indicate that its behavior more closely matches that found for cycles 15–21 rather than for cycles 9–14. Therefore, one infers that sunspot minimum for cycle 23 will occur in about 2–3 years, or about April 1996 to April 1997. Accepting the earlier date of first spotless day occurrence indicates that sunspot minimum for cycle 23 could come several months earlier, perhaps late 1995.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.  相似文献   

Solar rotation velocity as determined from sunspot drawings of J. Hevelius in the 17th century     

Claudia Abarbanell  Hubertus Wöhl 《Solar physics》1981,70(1):197-203

Using two original copies of Hevelius' Selenographia and reducing spot positions with two different methods, we found that the solar angular rotation velocity at the beginning of the Maunder minimum was about the same as today. The gradient of the differential rotation was slightly steeper than given in modern reductions, but not significantly different. These findings are in contradiction to those published by Eddy et al. (1976).  相似文献   

Coronal changes associated with a disappearing filament     

N. R. Sheeley Jr.  J. D. Bohlin  G. E. Brueckner  J. D. Purcell  V. E. Scherrer  R. Tousey  J. B. Smith Jr.  D. M. Speich  E. Tandberg-Hanssen  R. M. Wilson  A. C. De Loach  R. B. Hoover  J. P. Mc Guire 《Solar physics》1975,45(2):377-392

This paper describes Skylab/ATM observations of the events associated with a disappearing filament near the center of the solar disk on January 18, 1974. As the filament disappeared, the nearby coronal plasma was heated to a temperature in excess of 6 × 10⁶K. A change in the pattern of coronal emission occurred during the 11/3 hr period that the soft X-ray flux was increasing. This change seemed to consist of the formation and apparent expansion of a loop-like coronal structure which remained visible until its passage around the west limb several days later. The time history of the X-ray and microwave radio flux displayed the well-known gradual-rise-and-fall (GRF) signature, suggesting that this January 18 event may have properties characteristic of a wide class of X-ray and radio events.In pursuit of this idea, we examined other spatially-resolved Skylab/ATM observations of long-duration X-ray events to see what characteristics they may have in common. Nineteen similar long-lived SOLRAD X-ray events having either the GRF or post-burst radio classification occurred during the nine-month Skylab mission. Sixteen of these occurred during HAO/ATM coronagraph observations, and 7 of these 16 events occurred during observations with both the NRL/ATM slitless spectrograph and the MSFC-A/ATM X-ray telescope. The tabulation of these events suggests that all long-lived SOLRAD X-ray bursts involve transients in the outer corona and that at least two-thirds of the bursts involve either the eruption or major activation of a prominence. Also, these observations indicate that long-lived SOLARD events are characterized by the appearance of new loops of emission in the lower corona during the declining phase of the X-ray emission. However, sometimes these loops disappear after the X-ray event (like the post-flare loops associated with a sporadic coronal condensation), and sometimes the loops remain indefinitely (like the emission from a permanent coronal condensation).Visiting Scientist, Kitt Peak National Observatory, Tucson, Ariz. 85726, U.S.A. operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Presently located at NASA/MSFC, Space Sciences Laboratory, Marshall Space Flight Center, Ala. 35812, U. S.A.  相似文献   

The effect of iron on montmorillonite stability. (I) Background and thermodynamic considerations   总被引：1，自引：0，他引：1  

James Wilson  David Savage  Masahiro Shibata 《Geochimica et cosmochimica acta》2006,70(2):306-322

It is envisaged that high-level nuclear waste (HLW) will be disposed of in underground repositories. Many proposed repository designs include steel waste canisters and bentonite backfill. Natural analogues and experimental data indicate that the montmorillonite component of the backfill could react with steel corrosion products to produce non-swelling Fe-rich phyllosilicates such as chamosite, berthierine, or Fe-rich smectite. In K-bearing systems, the alteration of montmorillonite to illite/glauconite could also be envisaged. If montmorillonite were altered to non-swelling minerals, the swelling capacity and self-healing properties of the bentonite backfill could be reduced, thereby diminishing backfill performance. The main aim of this paper was to investigate Fe-rich phyllosilicate mineral stability at the canister-backfill interface using thermodynamic modelling. Estimates of thermodynamic properties were made for Fe-rich clay minerals in order to construct approximate phase-relations for end-member/simplified mineral compositions in logarithmic activity space. Logarithmic activity diagrams (for the system Al₂O₃-FeO-Fe₂O₃-MgO-Na₂O-SiO₂-H₂O) suggest that if pore waters are supersaturated with respect to magnetite in HLW repositories, Fe(II)-rich saponite is the most likely montmorillonite alteration product (if f_O2(g) values are significantly lower than magnetite-hematite equilibrium). Therefore, the alteration of montmorillonite may not be detrimental to nuclear waste repositories that include Fe, as long as the swelling behaviour of the Fe-rich smectite produced is maintained. If f_O2(g) exceeds magnetite-hematite equilibrium, and solutions are saturated with respect to magnetite in HLW repositories, berthierine is likely to be more stable than smectite minerals. The alteration of montmorillonite to berthierine could be detrimental to the performance of HLW repositories.  相似文献   

Regional record of a global oceanic anoxic event: OAE1a on the Apulia Platform margin, Gargano Promontory, southern Italy   总被引：1，自引：1，他引：1  

Valeria Luciani  Miriam Cobianchi  Claudia Lupi 《Cretaceous Research》2006,27(6):754-772

The Gargano Promontory of southern Italy, located on the eastern margin of the Apulia Platform, represents a peculiar Tethyan area where the transition between carbonate platform and adjacent basins is exposed on land. The Aptian stratigraphic record, represented in shallow-water, slope and deep-water deposits, provides a good opportunity to investigate the regional response to the worldwide documented climatic, biotic and palaeoceanographic changes related to Oceanic Anoxic Event 1a (OAE1a). A synthesis of data previously published (Ischitella and Coppitella sections), together with original data (Val Carbonara and Coppa della Guardia sections), from four stratigraphic sections from different depositional settings (proximal to distal) is provided, using an integrated, high-resolution micropalaeontological (planktonic foraminifera and calcareous nannofossils) and, for one section, geochemical (stable carbon and oxygen isotopes) approach. Organic matter preservation is confined to the more distal areas and consists of two thin intervals of black shales in the Aptian portion of the Marne a Fucoidi Formation. Biostratigraphic data assign the older black shale (5 cm thick) to the Selli Level equivalent (OAE1a, Lower Aptian); this carbon-rich interval is immediately followed by another black shale (7–10 cm thick) of early Late Aptian age.OAE1a is generally interpreted as a high-productivity event during a warming interval, followed by a cooling trend. In the Gargano Promontory, although the oxygen isotope curve indicates the above-mentioned climatic evolution, the micropalaeontological data do not support high fertility of the surface water, whereas micropalaeontological and geochemical data for the younger black shale do record high productivity (radiolarian increase in overall abundance, low nannofossil and foraminiferal species richness, increase in abudance of nannofossil fertility indices) associated with a cooling trend. The carbon and oxygen isotope record is in line with evidence from the curves documented elsewhere, whereas, among the biotic events, only the “nannoconid crisis” preceding OAE1a is revealed to be globally correlable.Environmental models for the two episodes of organic matter preservation are proposed, taking into account both global and local controlling factors.  相似文献   

Changes in the circulation of Tampa Bay due to Hurricane Frances as recorded by ADCP measurements and reproduced with a numerical Ocean model     

M. Wilson  S. D. Meyers  M. E. Luther 《Estuaries and Coasts》2006,29(6):914-918

Hurricane Frances is shown to greatly alter the hydrodynamics within Tampa Bay, Florida, and the exchange of water with the Gulf of Mexico in both observational data and a realistic numerical circulation model of the Tampa Bay estuary. Hurricane Frances hit Tampa Bay on September 5, 2004 with surface winds peaking twice near 22 m s⁻¹. There were three stages to the hydrodynamic effect of Frances on Tampa Bay. The first stage included the approach of Frances up to the first wind peak. The winds were to the south and southeast. During this stage sea level was maintained below mean sea level (MSL) and the residual current (demeaned, detided) was weak. The second stage began as the winds turned to the east and northeast, as the eye passed near the bay, and ended as the second wind peak appeared. During this stage the residual currents were strongly positive (into the bay), raising sea level to 1.2 m above MSL at St. Petersburg. The measured residual circulation peaked at over +0.7 m s⁻¹ near the surface. The model shows this velocity peak yielded a maximum volume flux into the bay of +44,227 m³ s⁻¹, displacing a total volume of 1.5 billion m³ in just a few hours, about 42% of the bay volume. In the third stage a strong negative flow developed as the wind and sea level relaxed to near normal levels. The ADCP measured a peak outflow of −0.8 m s⁻¹ during this time. Model results indicate a maximum flux of −37,575 m³ s⁻¹, and that it took about 50 h to drain the extra volume driven into the bay by Hurricane Frances.  相似文献   

Magnitudes, spatial scales and processes of environmental antimony mobility from orogenic gold–antimony mineral deposits, Australasia     

P. M. Ashley  D. Craw  M. K. Tighe  N. J. Wilson 《Environmental Geology》2006,51(4):499-507

Antimony (Sb) is strongly concentrated into hydrothermal mineral deposits, commonly with gold, in metasedimentary sequences around the Pacific Rim. These deposits represent potential point sources for Sb in the downstream environment, particularly when mines are developed. This study documents the magnitude and scale of Sb mobility near some mineral deposits in Australia and New Zealand. Two examples of New Zealand historic mining areas demonstrate that natural groundwater dissolution of Sb from mineral deposits dominates the Sb load in drainage waters, with Sb concentrations between 3 and 24 μg/L in major streams. Mine-related discharges can exceed 200 μg/L Sb, but volumes are small. Sb flux in principal stream waters is ca 1–14 mg/s, compared to mine tunnel fluxes of ca 0.001 mg/s. Dissolved Sb is strongly attenuated near some mine tunnels by adsorption on to iron oxyhydroxide precipitates. Similar Sb mobilisation and attenuation processes are occurring downstream of the historic/active Hillgrove antimony–gold mine of New South Wales, Australia, but historic discharges of Sb-bearing debris has resulted in elevated Sb levels in stream sediments (ca 10–100⁺ mg/kg) and riparian plants (up to 100 mg/kg) for ca 300 km downstream. Dissolution of Sb from these sediments ensures that river waters have elevated Sb (ca 10–1,000 μg/L) over that distance. Total Sb flux reaching the Pacific Ocean from the Hillgrove area is ca 8 tonnes/year, of which 7 tonnes/year is particulate and 1 tonne/year is dissolved.  相似文献   

Monte Carlo simulation of mixing in Ca3Fe2Ge3O12–Ca4Ge4O12 garnets and implications for the thermodynamic stability of pyrope–majorite solid solution     

Victor L. Vinograd  Bjoern Winkler  Daniel J. Wilson  Andrew Putnis  Julian D. Gale 《Physics and Chemistry of Minerals》2006,33(8-9):533-544

Static lattice energy calculations, based on empirical pair potentials, were performed for a large set of structures differing in the arrangement of octahedral cations within the garnet 2 × 2 × 2 supercell. The compositions of these structures varied between Ca₃Fe₂Ge₃O₁₂ and Ca₄Ge₄O₁₂. The energies were cluster expanded using pair and quaternary terms. The derived ordering constants were used to constrain Monte Carlo simulations of temperature-dependent mixing properties in the ranges of 1,073–3,673 K and 0–10 GPa. The free energies of mixing were calculated using the method of thermodynamic integration. The calculations predict a wide miscibility gap between Fe-rich (cubic) and Fe-pure (tetragonal) garnets consistent with recent experimental observations of Iezzi et al. (Phys Chem Miner 32:197–207, 2005). It is shown that the miscibility gap arises due to a very strong cation ordering at the Fe-pure composition, driven by the charge difference between Ca²⁺ and Ge⁴⁺ cations. The structural and thermodynamic analogies between Ca–Ge and Mg–Si systems suggest that a similar miscibility gap should exist between pyrope and Mg–Si-majorite.  相似文献