Cyclic and Long-Term Variation of Sunspot Magnetic Fields     

Alexei A. Pevtsov  Luca Bertello  Andrey G. Tlatov  Ali Kilcik  Yury A. Nagovitsyn  Edward W. Cliver 《Solar physics》2014,289(2):593-602

Measurements from the Mount Wilson Observatory (MWO) were used to study the long-term variations of sunspot field strengths from 1920 to 1958. Following a modified approach similar to that presented in Pevtsov et al. (Astrophys. J. Lett. 742, L36, 2011), we selected the sunspot with the strongest measured field strength for each observing week and computed monthly averages of these weekly maximum field strengths. The data show the solar cycle variation of the peak field strengths with an amplitude of about 500?–?700 gauss (G), but no statistically significant long-term trends. Next, we used the sunspot observations from the Royal Greenwich Observatory (RGO) to establish a relationship between the sunspot areas and the sunspot field strengths for cycles 15?–?19. This relationship was used to create a proxy of the peak magnetic field strength based on sunspot areas from the RGO and the USAF/NOAA network for the period from 1874 to early 2012. Over this interval, the magnetic field proxy shows a clear solar cycle variation with an amplitude of 500?–?700 G and a weaker long-term trend. From 1874 to around 1920, the mean value of magnetic field proxy increases by about 300?–?350 G, and, following a broad maximum in 1920?–?1960, it decreases by about 300 G. Using the proxy for the magnetic field strength as the reference, we scaled the MWO field measurements to the measurements of the magnetic fields in Pevtsov et al. (2011) to construct a combined data set of maximum sunspot field strengths extending from 1920 to early 2012. This combined data set shows strong solar cycle variations and no significant long-term trend (the linear fit to the data yields a slope of ??0.2±0.8 G?year^?1). On the other hand, the peak sunspot field strengths observed at the minimum of the solar cycle show a gradual decline over the last three minima (corresponding to cycles 21?–?23) with a mean downward trend of ≈?15 G?year^?1.  相似文献   

Reply to comment by J. G. Meert and R. Van der Voo on 'New palaeomagnetic result from Vendian red sediments in Cisbaikalia and the problem of the relationship of Siberia and Laurentia in the Vendian'     

Sergei A. Pisarevsky  Raisa A. Komissarova  Alexei N. Khramov 《Geophysical Journal International》2001,146(3):871-873

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The use of historical catch data to trace the influence of climate on fish populations: examples from the White and Barents Sea fisheries in the 17th and 18th centuries     

Lajus  Dmitry L.; Lajus  Julia A.; Dmitrieva  Zoya V.; Kraikovski  Alexei V.; Alexandrov  Daniel A. 《ICES Journal of Marine Science》2005,62(7):1426-1435

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Tomographic search for missing link between the ancient Farallon subduction and the present Cocos subduction     

Alexei Gorbatov  Yoshio Fukao 《Geophysical Journal International》2005,160(3):849-854

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Ice cover variability in the Caspian and Aral seas from active and passive microwave satellite data     

Alexei V. Kouraev  Fabrice Papa  Petr I. Buharizin  Anny Cazenave  Jean-Francois Cretaux  Julia Dozortseva  Frederique Remy 《Polar research》2003,22(1):43-50

The paper discusses time and space variations of ice extent in the Caspian and Aral seas during the last decade (1992-2002). It uses synergy of data from active (radar altimeter) and passive (radiometer) microwave nadir-looking instruments onboard the TOPEX/Poseidon satellite. The proposed approach is substantiated and validated using both in situ and satellite imagery data for the Caspian Sea. The results indicate significant spatial and temporal variability of ice conditions, with a significant decrease of both the duration of ice season and ice extent during the last four winters (1998-2002). The TOPEX/Poseidon-derived time series of sea ice extent are very valuable in view of the fragmentary and mostly unpublished data on ice conditions on the Caspian and Aral seas since the mid-1980s.  相似文献   

Modulation of Atmospheric 14C Concentration by the Solar Wind and Irradiance Components of the Hale and SCHWABE Solar Cycles     

Alexei N. Peristykh  Paul E. Damon 《Solar physics》1998,177(1-2):343-355

¹⁴C abundance on the Earth can be modulated by both the solar wind and irradiance components of the solar cycle. The magnetic field component of the solar wind modulates ¹⁴C production whereas the irradiance component can result in a change in the exchange rate between the various reservoirs of the carbon biogeochemical cycle. The effects would be nearly synchronous and difficult to separate. The 0.1% amplitude of irradiance variation during the two most recent solar cycles is well known. A 22-yr cycle exists also in the measured global temperature record.We have divided the University of Washington high-precision data on¹⁴C in tree rings into three 91-yr intervals: AD 1540–1630, 1630–1720 and 1715–1805, before, during and after the Maunder Minimum. Unfortunately the AD 1540–1630 interval includes part of the Spörer Minimum as well as the intermediate interval of high solar activity. These data were analyzed by the DFT, MEM and MTM methods of spectral time series analysis. The ca. 22-yr cycle is prominent during the Maunder Minimum, whereas the 11-yr cycle is most prominent after the Maunder Minimum but totally suppressed during the Maunder Minimum. The lesser amplitude of the 11-yr cycle before the Maunder Minimum is most probably due to overlap with the Spörer Minimum.Vasiliev and Kocharov VK83 have previously suggested that the 22-yr cycle persists through the Maunder Minimum whereas the 11-yr cycle is suppressed. Our calculations show that irradiance forcing of the carbon cycle during the 11-yr cycle is negligible, so the observed 11-yr cycle in¹⁴ C must be the result of production rate changes. The presence of the 22-yr cycle and suppression of the 11-yr cycle during the Maunder Minimum is in accord with a model by Jokipii Jok91.  相似文献   

Simulation of primary phase relations and mineral compositions in the Partridge River intrusion,Duluth Complex,Minnesota: implications for the parent magma composition     

Christopher I. Chalokwu  Norman K. Grant  Alexei A. Ariskin  Galina S. Barmina 《Contributions to Mineralogy and Petrology》1993,114(4):539-549

In order to describe the composition and crystallinity of the initial (parental) magma of the Partridge River intrusion of the Keweenawan Duluth Complex, and thereby understand the mode of emplacement and solidification of the intrusion, we have applied a numerical simulation technique called geochemical thermometry (Frenkel et al. 1988). The parental magma was a low-alumina, high-Ti-P olivine tholeiite similar to typical Keweenawan low-alumina, high-Ti-P basalts associated with the Duluth Complex and from the nearby Portage Lake area of the Lake Superior region. The parental magma was emplaced as a crystal-liquid suspension, followed by chilling of an evolved, leading edge ferrodioritic liquid in the basal zone of the intrusion. The conditions of emplacement at the present crustal location were 1,150°C, 2 kbar, and f _{O 2} slightly above the wustite-magnetite (WM) buffer. The main differentiation process after emplacement was the sorting and redistribution of plagioclase and olivine crystals on a local scale accompanied by less efficient convection and minor settling of olivine. Calculated crystallization sequence for the parental magma is olivine+plagioclase (1,240°C)olivine+plagioclase+magnetite (1,146°C, WM+0.5)olivine+plagioclase+magnetite+augite (1,140°C, WM+0.5). The calculated compositions of the cumulus olivine and plagioclase in equilibrium with the parent magma at 1,150°C are Fo_66.7±1.1 and An_64.5±2.5, respectively, and are similar to the estimated average composition of primary olivine (Fo_69.1±2.8) and the average composition of plagioclase core (An_66.3±2.8) measured in drill core samples through the intrusion (Chalokwu and Grant 1987).  相似文献   

Image decomposition of barred galaxies and AGN hosts     

Dimitri Alexei Gadotti 《Monthly notices of the Royal Astronomical Society》2008,384(1):420-439

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Active-Region Filaments and X-ray Sigmoids     

Pevtsov  Alexei A. 《Solar physics》2002,207(1):111-123

We use Yohkoh soft X-ray telescope data and H full-disk observations to study the evolution of chromospheric filaments and coronal sigmoids in 6 active regions in association with coronal mass ejections (CMEs). In two cases, CMEs are directly observed by the SOHO/LASCO C2 coronagraph. In four cases, other observations (magnetic clouds, geomagnetic storms, sigmoid-arcade evolution) are used as CME indicators. Prior to eruption, each active region shows a bright coronal sigmoidal loop and underlying H filament. The sigmoid activates, erupts and gets replaced by a cusp, or an arcade. In contrast, the H filament shows no significant changes in association with sigmoid eruption and CME. We explain these observations in a framework of the classical two-ribbon flare model.  相似文献   

First report of sablefish in spawning condition off the coast of Kamchatka and the Kuril Islands     

Orlov  Alexei M.; Biryukov  Igor A. 《ICES Journal of Marine Science》2005,62(5):1016-1020

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