Long transequatorial interconnecting loops of the new solar cycle     

FárnÍk  F.  Karlický  M.  Švestka  Z. 《Solar physics》1999,187(1):33-44

We study two long transequatorial loops connecting high-latitude regions of the new solar cycle. These loops (with lengths of 47 and 61 heliographic degrees) provide evidence that the upper length limit of 37° found by Chase et al. (1976) from Skylab data was determined simply by the typical distances between northern and southern active regions during the period of Skylab observations. We find strong support for the idea that these long interconnecting loops originate through reconnection of field lines extending from the two active regions towards and beyond the equator, and confirm the earlier finding by Canfield, Pevtsov, and McClymont (1996) that only field lines from active regions with the same chirality reconnect. As we are not aware of any longitudinal (E–W) loops of comparable lengths, we suggest that it is mainly the solar differential rotation which drives the reconnection of latitudinal (N–S) field lines.  相似文献   

Book reviews     

Wolf Tietze  Gerhard Kortum  W. R. Mead  T. K. Poiker  C. Paddick  George Kish  A. Njøs  H. Mensching  V. Haarmann  Uzo M. Igbozurike  M. M. Yoshino  Mushtaqur Rahman  Lage Wahlström  J. Connell  Kazimierz Dziewonski  Wayland R. Swain  J. Humlum  G. W. Lüttig  Haruko Kishimoto  Mai Britt E. Mørk 《GeoJournal》1982,6(3):270-280

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The solar abundance of thorium and lead     

Ø. Hauge  H. Sørli 《Solar physics》1973,30(2):301-308

Two new Th ii lines have been identified in the spectrum of the solar photosphere. The abundance derived from these lines together with the previously known Th ii line at 4019 Å, is log _Th = 0.85 ± 0.20 in the log _H = 12.00 scale. Analysis of three Pb i lines in the photospheric spectrum resulted in an abundance of log _pb = 1.90 ± 0.10. The solar Th/Pb ratio is: _Th/ _Pb = 0.09 _-0.005 ^0.09 .  相似文献   

Two types of extremely short lasting decimetric bursts and their possible relation to processes in solar magnetic traps     

Øystein Elgarøy  Ole P. Sveen 《Solar physics》1973,32(1):231-240

High resolution spectral observations between 500 MHz and 550 MHz on 1972 October 25, revealed an emission event of special interest. The main feature was bursts with a single frequency duration of about 0.09 s and with a bandwidth of the same order of magnitude as the band covered by the spectrograph. The bursts occurred in showers' which lasted for one or two minutes and which were separated by quiet intervals of roughly the same length. Frequently the activity assumed a periodic nature. Periods between 0.1 s and 0.3 s were found. The most remarkable feature of the records was a very large number of bursts with the same duration as the wide band bursts, but showing a bandwidth of a mere 1–2 MHz.The wide band bursts may be plasma waves excited by proton streams trapped in coronal magnetic fields and the narrow band bursts may possibly be explained as perpendicular electrostatic electron cyclotron waves.  相似文献   

Temperature variation at mesopause levels during winter solstice at 78°N     

H.K. Myrabø 《Planetary and Space Science》1984,32(2):249-255

Atmospheric temperatures from the polar mesopause are deduced from spectrophotometric measurements of hydroxyl bands and lines in the night airglow made at 78°N during December and January 1980/81 and 1982/83. An overall mean temperature of 220 K is found with a range from 172 to 257 K in the daily mean values. Several warm periods lasting 3–6 days may be due to heat dissipated by gravity waves. One week of consistently low temperatures was apparently connected to a stratospheric warming. Both datasets show a warmer mean temperature later in January than for early and mid-December. The polar OH airglow seems to peak at or just above the mesopause. The data also indicate that the mesopause is situated at approx. 90 km with an upper temperature gradient of 1 K km^?1 indicating a very shallow mesopause. A superposed epoch analysis of 19 consecutive 24-h periods reveals a semidiurnal variation in the temperature around winter solstice with an amplitude of 5 K. No diurnal variation of amplitude greater than 1 K is apparent. Average wind velocity deduced from the amplitude of the semidiurnal temperature variation is 9 m s^?1.  相似文献   

Chemical Mechanism Development: Laboratory Studies and Model Applications     

Harald Geiger  Ian Barnes  Karl H. Becker  Birger Bohn  Theo Brauers  Birgit Donner  Hans-Peter Dorn  Manfred Elend  Carlos M. Freitas Dinis  Dirk Grossmann  Heinz Hass  Holger Hein  Axel Hoffmann  Lars Hoppe  Frank Hülsemann  Dieter Kley  Björn Klotz  Hans G. Libuda  Tobias Maurer  Djuro Mihelcic  Geert K. Moortgat  Romeo Olariu  Peter Neeb  Dirk Poppe  Lars Ruppert  Claudia G. Sauer  Oleg Shestakov  Holger Somnitz  William R. Stockwell  Lars P. Thüner  Andreas Wahner  Peter Wiesen  Friedhelm Zabel  Reinhard Zellner  Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357

Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere.  相似文献   

Turning climate change information into economic and health impacts     

Kirsten Halsnæs  Jesper Kühl  Jørgen E. Olesen 《Climatic change》2007,81(1):145-162

The PRUDENCE project has generated a set of spatially and temporally high-resolution climate data, which provides new opportunities for assessing the impacts of climate variability and change on economic and human systems in Europe. In this context, we initiated the development of new approaches for linking climate change information and economic studies. We have considered a number of case studies that illustrate how linkages can be established between geographically detailed climate data and economic information. The case studies included wheat production in agriculture, where regional climate data has been linked to farm enterprise data in an integrated model of physical conditions, production inputs and outputs, and farm management practices. Similarly, temperature data were used to assess consequences of extreme heat and excess mortality in urban areas. We give an introduction of an analytical approach for assessing economic impacts of climate change and discuss how economic concepts and valuation paradigms can be applied to climate change impact evaluation. A number of methodological difficulties encountered in economic assessments of climate change impacts are described and a number of issues related to social and private aspects of costs are highlighted. It is argued that, in particular, detailed climate information matters in relation to understanding how private agents react to observed climate data.  相似文献   

Changes in size distribution of fresh water nanoscale colloidal matter and associated elements on mixing with seawater   总被引：1，自引：0，他引：1  

Björn Stolpe  Martin Hassellöv 《Geochimica et cosmochimica acta》2007,71(13):3292-3301

Changes in size distribution and elemental composition of 0.5-50 nm fresh water colloids during estuarine mixing have been studied by in-laboratory mixing of natural creek water and synthetic seawater, followed by size fractionation with Asymmetrical Flow Field-Flow Fractionation, and online elemental quantification by High-Resolution ICPMS. At least two types of colloids were present in the studied size region; 0.5-3 nm fluorescent dissolved organic matter (FDOM), and >3 nm colloids that were rich in Fe and colored dissolved organic matter (CDOM). Most trace elements were associated in different proportions to these two populations of colloids. Following mixing with synthetic seawater, the >3 nm Fe-rich colloids and CDOM were extensively removed from the studied size region by salt induced aggregation. The degree of removal with increasing salinity was greatest below 2.5‰ salinity, continued to a lesser degree between 2.5‰ and 15‰ salinity, above which only very small additional removal could be distinguished. At 25‰ salinity, the Fe concentration in the 0.5-50 size region had been reduced down to 15% of its original value in freshwater, while the amount of CDOM had been reduced to 55%. On the contrary, the concentration of the 0.5-3 nm FDOM was unchanged by the increased concentration of sea salt. Therefore, colloidally associated Al, P, Co, Cu, Zn, Ce, Lu and Pb were removed from the 0.5-50 nm size region according to their relative distributions between the FDOM and the Fe-rich colloids. Consequently, at 25‰ salinity, the 0.5-50 nm concentrations of Al, Mn, P and Pb, (mainly associated with the Fe-rich colloids) had been reduced down to 13-26 % of their values in freshwater, while the concentrations of Co and Cu (with higher preferences for FDOM) were less reduced, down to 46% and 57%, respectively. Changes in the elemental composition of the remaining colloidal matter were observed, the most pronounced were increased contents of P, Al and Pb in Fe-rich colloidal matter of medium size (∼3-15 nm) and increased Pb content in Fe-rich colloidal matter of larger size (∼5-50 nm).  相似文献   

A dinoflagellate cyst record of Holocene climate and hydrological changes along the southeastern Swedish Baltic coast     

Shi-Yong Yu  Björn E. Berglund 《Quaternary Research》2007,67(2):215-224

A high-resolution, well-dated dinoflagellate cyst record from a lagoon of the southeastern Swedish Baltic Sea reveals climate and hydrological changes during the Holocene. Marine dinoflagellate cysts occurred initially at about 8600 cal yr BP, indicating the onset of the Littorina transgression in the southeastern Swedish lowland associated with global sea level rise, and thus the opening of the Danish straits. Both the species diversity and the total accumulation rates of dinoflagellate cysts continued to increase by 7000 cal yr BP and then decreased progressively. This pattern reveals the first-order change in local sea level as a function of ice-volume-equivalent sea level rise versus isostatic land uplift. Superimposed upon this local sea level trend, well-defined fluctuations of the total accumulation rates of dinoflagellate cysts occurred on quasi-1000- and 500-yr frequency bands particularly between 7500 and 4000 cal yr BP, when the connection between the Baltic basin and the North Atlantic was broader. A close correlation of the total accumulation rates of dinoflagellate cysts with GISP2 ice core sea-salt ions suggests that fluctuations of Baltic surface conditions during the middle Holocene might have been regulated by quasi-periodic variations of the prevailing southwesterly winds, most likely through a system similar to the dipole oscillation of the modern North Atlantic atmosphere.  相似文献   

Is pure groundwater safe to drink?: natural "contamination' of groundwater in Norway   总被引：1，自引：0，他引：1  

David Banks  Aase Kjersti Midtgrd  Geir Morland  Clemens Reimann  Terje Strand  Kjell Bjorvatn  & Ulrich Siewers 《Geology Today》1998,14(3):104-113

The title of this article is designed to provoke. Naturally occurring parameters are, by definition, not contamination. Nevertheless, nature is not necessarily nice, and naturally occurring trace toxins can be every bit as undesirable as their counterparts derived from human pollution.  相似文献