Evidence for the Blake event in volcanic rocks from Lipari (Aeolian Archipelago)     

Elena Zanella  & Marinella A. Laurenzi 《Geophysical Journal International》1998,132(1):149-158

Palaeomagnetic and geochronological measurements have been carried out on the late Pleistocene basaltic–andesitic unit of Monte Chirica–Costa Rasa, on the island of Lipari (Aeolian Archipelago). The lava flow sequence is about 10  m thick and has been sampled in detail. Magnetic properties are rather uniform; Curie temperatures of 540° to 580 °C, and the saturation IRM reached at applied values of 0.1  T point to titanomagnetite as the main magnetization carrier. Thermal and AF demagnetization have shown the presence of secondary magnetization components. These were removed mostly at 450°–500 °C or 20–30  mT, indicating a highly stable ChRM with directions from transitional to reverse. Where a ChRM could not be isolated by application of the demagnetization techniques, the converging remagnetization circles method gave a mean ChRM value fully comparable with that obtained from other methods. ⁴⁰Ar/³⁹Ar determinations were performed on two lava flows, in the lower and upper parts of the sequence. The former shows a transitional ChRM direction and a whole-rock age of 157±12  ka, the latter a reverse direction, a whole-rock age of 143±17  ka and a ground-mass age of 128±23  ka. The radiometric data and the reconstructed stratigraphy, which indicate ages of 150±10  ka and 104±3.5  ka, respectively, for the volcanic units at the bottom and top of the Monte Chirica–Costa Rasa unit, suggest that the reverse directions recorded in Lipari are related to the Blake event.  相似文献   

Igneous zircon: trace element composition as an indicator of source rock type   总被引：225，自引：2，他引：225  

E. Belousova  W. Griffin  Suzanne Y. O'Reilly  N. Fisher 《Contributions to Mineralogy and Petrology》2002,143(5):602-622

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Of Time and Tide: Comments on Newby and Webb, 1994     

Dena F. Dincauze  Elena Decima 《Quaternary Research》1995,44(3)

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Hydrological response to radar rainfall maps through a distributed model     

Ignazio Becchi  Enrica Caporali  Elena Palmisano 《Natural Hazards》1994,9(1-2):95-108

Weather radars in investigating physical characteristics of precipitation are becoming essential instruments in the field of short term meteorological investigation and forecasting. To analyze the radar signal impact in hydrological forecasting, precipitation input fields, generated through a statistical mathematical model, are supplied to a distributed hydrological model. Such a model would allow the control of the basin response to precipitation measurements obtained by a meteorological radar and, in the meanwhile, to evaluate the influence of distributed input. The distributed model describes the basin hydrological behavior, subdividing it into distinct geometrical cells and increasing the physical significance by reproducing the distributed hydrographic basins characteristics, such as infiltration capacity, runoff concentration time, network propagation speed, soil moisture influence. Each basin cell is characterized by its geological, pedological and morphological status, and may be considered a unitary hydrological system, linked to the others by geomorphological and hydraulic relationships. To evaluate the dynamics of the flood event a synthetic representation of the channel network is introduced, where each stream branch is modeled as a linear reservoir. Finally, the discharge in the outlet section is derived, taking into account the hydraulic characteristics of the upstream branches.  相似文献   

SporadicE-layer ionization and sunspot cycle     

Mario Bossolasco  Antonio Elena 《Pure and Applied Geophysics》1963,56(1):142-149

Summary The correlation between the sunspot cycle and the sporadicE-layer ionization is investigated at middle latitudes. Higher mean values off ₀Es occur generally with higher sunspot numbers. Some evidence for a phase-shift between long term time-variation in sunspot numbers andf ₀Es is obtained. The solar cycle variation ofEs is somewhat larger over the Far East. Regarding the behaviour of the time-development ofEs events in diurnal variation, an interpretation is proposed.  相似文献   

On the lunar semidiurnal variation of theD andF2 layers     

M. Bossolasco  A. Elena 《Pure and Applied Geophysics》1960,46(1):167-172

Summary The lunar semidiurnal variation of ionospheric absorption at Freiburg and of thef ₀ F2 at, Genova, Freiburg and Léopoldville has been deduced. The results are compared with those obtained by other Authors. Magnetic dip, rather than geomagnetic latitude, is found to be a parameter controlling the morphology of the lunar semidiurnal variation of theF2 layer. Finally, a graphical representation of the amplitude of lunar semidiurnal variation off ₀ F2 as function of the magnetic dip is also given.

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Riassunto Viene determinata la variazione lunare semidiurna dell'assorbimento ionosferico per Friburgo e della frequenza critica dello stratoF2 per Genova, Friburgo, Léopoldville. I risultati sono confrontati con quelli ottenuti da altri Autori per varie stazioni situate in diverse parti del globo. In particolare si trova che la inclinazione magnetica, meglio della latitudine geomagnetica, è il parametro che regola la morfologia della variazione lunare inF2. Infine si dà una rappresentazione grafica dell'ampiezza della variazione lunare dellaf ₀ F2 come funzione dell'inclinazione magnetica.

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This research was supported by a grant from the Committee on Lunar Variation (IAGA). The paper has been presented at the XII-Assembly of the I.G.G.U. in Helsinki (July–August 1960).  相似文献   

The 27-Day Signal in Sunspot Number Series and the Solar Dynamo     

Jean-Louis Le Mouël  Mikhail G. Shnirman  Elena M. Blanter 《Solar physics》2007,246(2):295-307

We analyze the Wolf number daily series WN (1849 to present) as well as two other related series characterizing solar activity. Our analysis consists in computing the amplitude of a given Fourier component in a sliding time window and examining its long-term evolution. We start with the well-known 27.03- and 27.6-day periods and observe strong decadal variations of this amplitude as well as a sharp increase of the average value starting around 1905. We then consider a packet of 31 lines with periods from 25.743 to 28.453 days, which is shown to be a better representation of the synodic solar rotation. We first examine the temporal evolution of individual lines, then the energy of the packet. The energy of the packet increases sharply at the beginning of the 20th century, leading by more than two decades the well-known increase of the Wolf number. The nonaxisymmetry of sunspots increases before the total increase of activity and may be considered as a precursor. We discuss briefly and tentatively this observation in terms of solar dynamo theory.  相似文献   

Synthetic Spectra of the Fe VIII  – Fe XVI Emission Lines for Electron Non-Thermal Distributions     

Elena Dzifčáková  Danica Tóthová 《Solar physics》2007,240(2):211-226

A certain class of non-thermal electron distributions can exhibit more mono-energetic shape and a higher peak than the Maxwellian distribution. This type of electron distribution can be observed mainly in flaring plasmas. We have studied the influence of this kind of electron energy distribution on the excitation equilibrium of Fe VIII – Fe XVI in the solar corona. The changes in synthetic spectra of the emission lines belonging to these ions due to this non-thermal distribution are shown. The possibilities of finding the shape of the energy distribution function of electrons from the Fe line ratios are also discussed. The results can be used for diagnostics of coronal plasmas where the deviations of particle energy distributions from the Maxwellian one can be significant.  相似文献   

Geochronological and isotopic constraints on Palaeoproterozoic skarn base metal mineralisation in the central Gawler Craton, South Australia   总被引：1，自引：0，他引：1  

Anthony Reid  Richard Flint  Roland Maas  Katherine Howard  Elena Belousova 《Ore Geology Reviews》2009,36(4):350-362

The mineralisation potential of Palaeoproterozoic strata from the central Gawler Craton, South Australia, is poorly known. This study defines the timing of Zn-rich skarn formation within Palaeoproterozoic calcsilicate and highlights this as a new mineralisation style for the Gawler Craton. Sulphides within the garnet–diopside skarn in the No. 17 Bore Prospect are predominantly in the form of sphalerite, associated with galena, minor chalcopyrite, pyrrhotite and pyrite. Sulphide is present in disseminated form and as a coarse-grained sulphide within a sericite-rich cavity-fill. Mineralisation is inferred to have formed at 1710 ± 16 Ma through a Sm–Nd isochron from garnet and diopside aliquots. A weakly mineralised and altered granite immediately below the calcsilicate skarn crystallised at 1729 ± 13 Ma (LA-ICPMS U–Pb zircon), within error of the skarn mineralisation. The skarn is interpreted to have formed through the initiation of fluid circulation as a result of high-level granite emplacement within the Palaeoproterozoic strata. Exploration for skarn Zn–Pb deposits such as the No. 17 Bore Prospect is assisted by their geophysical properties.  相似文献   

First isotopic data on detrital zircons from the Engane-Pe Uplift (western Polar Urals): Implications for the primary tectonic position of the Pre-Uralides-Timanides     

N. B. Kuznetsov  L. M. Natapov  E. A. Belousova  W. L. Griffin  S. Y. O’Reilly 《Doklady Earth Sciences》2009,426(1):567-573

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