Macroscopic motions in prominences     

Marcos E. Machado  Hugo Grossi Gallegos 《Solar physics》1972,23(2):340-345

Macroscopic velocity fields have been studied in a solar prominence. The spectra and monochromatic images were analyzed, and the existence of a contracting motion, possibly due to a pinch effect, is discussed. A helical shape of the prominence is proposed.  相似文献   

An evidence of flare energy buildup and release related to magnetic shear and reconnection     

Marcos E. Machado 《Solar physics》1985,99(1-2):159-166

We study series of homologous flares, observed in the active region NOAA 2372 by the HXIS on the Solar Maximum Mission and ground based observatories. Changes in the flare homology, particularly those related to the location of the hard X-ray emission, show clear correlation with the development of magnetic shear within the active region. Following our early study (Machado et al., 1983) we propose that magnetic shear and reconnection are necessary for high power energy release, but the former may not be a sufficient condition in an isolated magnetic loop. These results are discussed within the context of a broader study, in order to explore their generality.  相似文献   

Secular variation of seismo-volcanic phenomena in the azores     

Frederico Machado 《Bulletin of Volcanology》1960,23(1):101-108

By studying the past behaviour of Azorean volcanoes, sunspot and Earth tide correlations have been discovered, and may certainly help in prediction. Some evidence has also been found that buckling of the thin roof of magma chambers may be the mechanism responsible for the eruptions, including the accompanying seismic swarms. If this is the case, geodetic control of the adjacent regions will probably be decisive in forecasting future activity.  相似文献   

Oceanic fissure eruptions,subvolcanic intrusions and volcanic magma Chambers     

F. Machado 《Bulletin of Volcanology》1969,33(4):1229-1236

Rifting along the mid-Atlantic ridge seems to have been accompanied by fissure eruptions which flooded the ocean bottom. Locally these plateau lavas rose above sea level and erosion revealed plutonic bodies emplaced within them. There is also some evidence of shallow magma chambers feeding surface volcanism. All these facts can be conveniently interpreted by assuming fractional melting of the upper mantle, at depths below about 50 km, and a pulsation of the pressure, produced by a varying gravitation, which seems capable of squeezing the molten fraction and of fracturing the solid crust above. Magma chambers can then be formed, probably by subterranean cauldron subsidence of Scottish type, they can leed surface volcanoes and will eventually solidify as plutonic bodies. Phase changes of eclogite, possibly present in the oceanic upper mantle, could also explain the uplift of island platforms.  相似文献   

Activity of the Atlantic volcanoes, 1947–1965     

F. Machado 《Bulletin of Volcanology》1967,30(1):29-34

A remarkable sequence of volcanic eruptions were observed in the Atlantic, during the last 20 years: Hckla in 1947, La Palma in 1949, Fogo in 1951, Fayal in 1957, Tristan da Cunha in 1961, Askja in 1961, Surtsey in 1963 (and possibly San Jorge in 1964). The long-period components of the Earth tide seem to influence the eruptive epochs, acting as trigger-forces.  相似文献   

Diurnal evolution of solar radiation at the surface in the city of São Paulo: seasonal variation and modeling     

A. P. de Oliveira  A. J. Machado  J. F. Escobedo  J. Soares 《Theoretical and Applied Climatology》2002,71(3-4):231-249

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Opening geometry of the Kurile Basin (Okhotsk Sea) as inferred from structural data   总被引：1，自引：0，他引：1  

Boris Baranov  How Kin Wong  Karina Dozorova  Boris Karp  Thomas Lüdmann  Viktor Karnaukh 《Island Arc》2002,11(3):206-219

Abstract   The Kurile Basin in the Okhotsk Sea, northwestern Pacific, is a back-arc basin located behind the Kurile Island Arc. It is underlain by oceanic crust and its origin has been attributed to back-arc spreading. Two models for the opening of the Kurile Basin exist, for which the spreading axis is oriented northeast–southwest and northwest–southeast, respectively. New data are presented here on the morphostructure of the slope of the northern Kurile Basin and of the central Kurile Basin which support a strike of the spreading axis in the latter direction. Bathymetric as well as single-channel and multichannel seismic reflection data demonstrate the existence of dominant northwest-striking normal faults on the northern slope of the Kurile Basin. In the central Kurile Basin a basement rise striking north-northwest–south-southeast (here named the Sakura Rise) was mapped. The rise morphology has the distinct imprint of a rift structure with symmetrical volcanic edifices on the rise axis and faulted blocks that tilt in opposite directions on the flanks. These data suggest that the Kurile Basin opened in a northeast–southwest direction. In the generally accepted plate tectonic reconstructions, northwest–southeast spreading associated with dextral strike–slip along the north–south-striking shear zone of Sakhalin and Hokkaido islands has been assumed. In the present model, spreading in the Kurile Basin was presumably connected with dextral displacement along a northeast-striking shear zone on the southern segment of the Okhotsk Sea.  相似文献   

Origin and depositional environment of the china clay deposits of south Kerala     

K Soman  Terry Machado 《Journal of Earth System Science》1986,95(2):285-292

Results of petrographic, mineralogic and granulometric studies of the sedimentary china clay deposits of Trivandrum district in south Kerala are discussed in terms of their origin and depositional environment. While mineralogic data indicate a khondalitic source for the kaolins as against the hitherto postulated leptynitic source, petrographic evidences suggest that most of the kaolinite were transported from the weathering crust and deposited. Granulometric data and SEM scanning of sand grains from the clays indicate their deposition in a fluvial/low energy littoral environment under conditions of subaqueous agitation.  相似文献   

Privatising public space in post-apartheid South African cities through neighbourhood enclosures     

Karina Landman 《GeoJournal》2006,66(1-2):133-146

In the past five years the numbers of enclosed neighbourhoods have significantly increased in South Africa. These are existing neighbourhoods that are closed off through gates and booms across the roads. Many of these neighbourhoods are fenced or walled off as well, with a limited number of controlled entrances/exits, manned by security guards in some cases. The roads within these neighbourhoods were previously, or still are public property and in most cases the local council is still responsible for public services to the community within the enclosed neighbourhoods. In this way public urban space is privatised, whether formally or informally. I will explore the distribution of enclosed neighbourhoods in South Africa on a national scale and within two metropolitan municipalities, viz., the cities of Johannesburg and Tshwane. Then I proceed to highlight the nature and impact of these neighbourhoods on the privatisation of public space and draw on a wide basis of empirical data obtained through a national survey and in-depth case studies. Finally I will conclude with examples of lessons learnt from South Africa and how these may relate to international experience and future research on gated communities.  相似文献   

Book reviews     

M. E. Machado  A. Duijveman  C. J. Schrijver 《Solar physics》1982,79(2):399-400

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