Out of the Lab and into the Frying Pan: The Need for Broader Conversations about Climatic Change     

Stewart J. Cohen 《Climatic change》1999,41(3-4):265-270

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Radio mapping of the heliospheric current sheet     

R. T. Stewart 《Solar physics》1971,109(1):139-147

Synoptic plots of solar radio noise storms in the interval 1973 to 1984 are described. The dividing line between opposite noise storm polarities appears to be a good representation of the heliospheric current sheet out to displacements in latitude of ± 50° from the solar equator. This result is surprising, because noise storms are closely associated with closed magnetic field regions near sunspots. The possibility that noise storm polarity is determined by mode coupling high in the corona, where field lines are open, can be ruled out by the available evidence. This leads us to conclude that it is the clustering in longitude of active region complexes which determines the sector structure of the interplanetary magnetic field.  相似文献   

The jet in M87     

P. Stewart 《Astrophysics and Space Science》1971,14(2):261-264

The jet is assumed to be ejected from the nucleus supersonically into a gas which is at rest; the knots that result are related to those which are observed and an estimate of the jet temperature follows. The magnetic field and particle density inside the jet are discussed and observations are suggested.  相似文献   

The detrital zone in the shorty crater cores     

J. Stewart Nagle 《Earth, Moon, and Planets》1978,18(4):499-517

The lower part of lunar cores 74002/1 contains pure fine-grained black soil grading upward to orange soil. The section, however, between 10 cm and the lunar surface contains a mixture of orange and dark soil with a clast-in-matrix texture and some agglutinates. Therefore, this upper section is interpreted as a detrital zone. Although Shorty Crater was formed approximately 30 m.y. ago, all indicators of soil age give a much shorter time for residence of the detrital zone. Both absolute agglutinate content and authigenic agglutinate content indicate a surface residence of less than 8 m.y. for the detrital portion of the core. Most calculated ages of the detrital zone cluster are around 3 m.y. Grain size distribution is characteristic of an immature soil and there is little evidence, indicated by lack of upward fining and decrease in coarsest grain sizes, ofin situ maturation of the section. Mixing with adjacent soils is very low, even though such soils lie only 0.5 M from the sampling site. Four of the five sub-strata in the upper 10 cm could have been produced by the impact event that produced the 20 M wide boulder field near the sampling site on the Shorty Crater rim. This event would distribute perched clasts over the sampling site. Thickness of the detrital part of the section is in keeping with its being ejecta from the boulder bed crater. The thickness of the agglutinate-rich zone, 1.5 cm, is reasonable for a less-than 4 m.y. residence time.  相似文献   

On the contraction of the Earth     

A. D. Stewart 《Earth, Moon, and Planets》1979,21(1):123-124

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Evolution of polar coronal holes and sunspots during cycles 21 and 22     

S. Bravo  G. Stewart 《Solar physics》1994,154(2):377-384

A very good correlation between the evolution of polar coronal hole size and sunspot number half a solar cycle later was found by Bravo and Otaola for solar cycle 21. In this paper we use a more complete set of data to reanalyse the relationship for solar cycle 21 and investigate the same relationship for solar cycle 22. We find that the complete set of data for cycle 21 yields a slightly different time shift for the best correlation between sunspots and holes and that the time shift for cycle 22 is different from that of cycle 21. However, because of limited availability of data of cycle 22, we consider it necessary to wait until the end of this cycle in order to decide if the difference is statistically significant or not. We also found that the time between successive peaks of smoothed polar hole area and smoothed sunspot number is the same in both cycles. This may provide a useful tool for the forecasting of future sunspot maxima. The constant of proportionality between polar coronal hole area and sunspot number can be seen to be different in both cycles. We discuss this difference and interpret it in terms of a different magnitude of the polar field strength in the two cycles.  相似文献   

Some newly discovered coronal emission lines from high altitude infrared observations of the 7 March, 1970, solar eclipse     

Kenneth H. Olsen  Charles R. Anderson  John N. Stewart 《Solar physics》1971,21(2):360-371

A survey of the infrared coronal spectrum between 1 and 3 was made from a high altitude aircraft during the 7 March, 1970, solar eclipse. The observations were made with a Fourier transform spectrometer and were confined to the outer chromosphere and inner corona. In addition to well known chromospheric lines of Hi and Hei, nine additional lines were seen. Evidence is presented for the tentative assignment of these lines to forbidden transitions in highly ionized atoms of magnesium, aluminum, silicon, sulphur, and chromium.  相似文献   

HIDEEP – an extragalactic blind survey for very low column-density neutral hydrogen     

R. F. Minchin  M. J. Disney  P. J. Boyce  W. J. G. de Blok  Q. A. Parker  G. D. Banks †  K. C. Freeman  D. A. Garcia  B. K. Gibson  M. Grossi  R. F. Haynes  P. M. Knezek  R. H. Lang  D. F. Malin  R. M. Price  I. M. Stewart  A. E. Wright 《Monthly notices of the Royal Astronomical Society》2003,346(3):787-802

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Radiative losses in a magnetostatic and intense electromagnetic field     

H. R. Standeven  P. Stewart 《Astrophysics and Space Science》1972,19(1):181-187

The average energy radiation rate is calculated exactly for the case of a charged particle injected with arbitrary momentum into an intense electromagnetic field which is propagating along a uniform magnetostatic field. The treatment is relativistic.  相似文献   

A laboratory simulation of pyroclastic flows down slopes     

Herbert E. Huppert  J.Stewart Turner  Steven N. Carey  R. Stephen  J. Sparks  Mark A. Hallworth 《Journal of Volcanology and Geothermal Research》1986,30(3-4)

Laboratory experiments are described which explore the dynamical consequences of buoyant convective upflow observed above hot pyroclastic flows. In nature, the convection is produced by the hot ash particles exchanging heat with air mixed into the front and top of the pyroclastic flow. This effect on the buoyancy due to the mixing of air and ash has been modelled in the laboratory using mixtures of methanol and ethylene glycol (MEG), which have a nonlinear density behaviour when mixed with water. Intermediate mixtures of these fluids can be denser than either initial component, and so the laboratory experiments were inverted models of the natural situation. We studied MEG flowing up under a sloping roof in a tank filled with water. The experiments were performed both in a narrow channel and on a laterally unconfined slope. The flow patterns were also compared with those of conventional gravity currents formed using fresh and salt water. The presence of the region of reversed buoyancy outside the layer flowing along the slope had two significant effects. First, it periodically protected the flow from direct mixing with the environment, resulting in pulses of relatively undiluted fluid moving out intermittently ahead of the main flow. Second, it produced a lateral inflow towards the axis of the current which kept the current confined to a narrow tongue, even on a wide slope.In pyroclastic flows the basal avalanche portion has a much larger density contrast with its surroundings than the laboratory flows. Calculations show that mixing of air into the dense part of a pyroclastic flow cannot generate a mixture that is buoyant in the atmosphere. However, the overlying dilute ash cloud can behave as a gravity current comparable in density contrast to the laboratory flows and can become buoyant, depending on the temperature and ash content. In the August 7th pyroclastic flow of Mount St. Helens, Hoblitt (1986) describes pulsations in the flow front, which are reminiscent of those observed in the experiments. As proposed by Hoblitt, the pulsations are caused by the ash cloud accelerating away from the front of the dense avalanche as a density current. The ash cloud then mixes with more air, becomes buoyant and lifts off the ground, allowing the avalanche to catch up with and move ahead of the cloud. The pulsing behaviour at the fronts of pyroclastic flows could account for the occurrence of cross-bedded layer 1 deposits which occur beneath layer 2 deposits in many sequences.  相似文献