Publisher's announcement     

Peter Martinez 《Astrophysics and Space Science》1989,155(2):iii-iii

Publisher's announcement  相似文献   

Electron acceleration in solar flares     

Wolfgang Dröge  Peter Meyer  Paul Evenson  Dan Moses 《Solar physics》1989,121(1-2):95-103

For the period September 1978 to December 1982 we have identified 55 solar flare particle events for which our instruments on board the ISEE-3 (ICE) spacecraft detected electrons above 10 MeV. Combining our data with those from the ULEWAT spectrometer (MPI Garching and University of Maryland) electron spectra in the range from 0.1 to 100 MeV were obtained. The observed spectral shapes can be divided into two classes. The spectra of the one class can be fit by a single power law in rigidity over the entire observed range. The spectra of the other class deviate from a power law, instead exhibiting a steepening at low rigidities and a flattening at high rigidities. Events with power-law spectra are associated with impulsive (<1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (<1 hr) soft X-ray emission. The characteristics of long-duration events are consistent with diffusive shock acceleration taking place high in the corona. Electron spectra of short-duration flares are well reproduced by the distribution functions derived from a model assuming simultaneous second-order Fermi acceleration and Coulomb losses operating in closed flare loops.  相似文献   

Stochastic models for the completeness of stratigraphic sections     

David Strauss  Peter M. Sadler 《Mathematical Geology》1989,21(1):37-59

Properties of stratigraphic completeness are determined here from a Brownian motion model of sediment accumulation. This avoids flaws inherent in application of a discrete-time random walk to the time span, rather than thickness, of sediment layers. Both discrete and continuous models show that the concept of stratigraphic completeness is meaningful only when the time scale is specified. From the discrete model, not surprisingly, completeness improves with increasing relative frequency and average thickness of depositional increments and the error of completeness estimation should decrease for longer sections. The continuous model shows that two dimensionless products determine the probability that a given time interval will be recorded by some preserved sediment. The first is the ratio of the age of the interval to its time span; the second is the product of the square root of the time span and ratio of the mean to the standard deviation of accumulation rate. Expected completeness is the average of these probabilities for all successive intervals of the given time span. For long sections, completeness may be estimated from the second dimensionless product alone. The two dimensionless products are sufficient to predict the relationship of accumulation rate to time span, the distribution of bed thickness, and the weak association of completeness and section thickness.  相似文献   

Fault plane solutions of earthquakes and active tectonics of the Tibetan Plateau and its margins   总被引：18，自引：0，他引：18  

Peter Molnar  Hélène Lyon-Caent 《Geophysical Journal International》1989,99(1):123-154

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Environmental atlas of the Potomac Estuary: A. J. Lippson,M. S. Haire,A. F. Holland,F. Jacobs,J. Jensen,R. L. Moran-Johnson,T. T. Polgar and W. A. RichkusJohns Hopkins University Press,Baltimore & London, 1981, 280 pp+9 Folio Maps, £20·00     

J.B. Wilson 《Estuarine, Coastal and Shelf Science》1983,17(5):592-593

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Bouguer gravity profiles across the highland-lowland escarpment on Mars     

Peter Janle 《Earth, Moon, and Planets》1983,28(1):55-67

Selected Bouguer gravity profiles crossing the highland-lowland boundary of Mars are calculated. Density-depth models are presented for two areas. All profiles show an isostatic behaviour of the ancient highlands and the adjacent lowlands. Especially isostasy must be implied for the area of the escarpment. It is found that the whole Elysium dome is also nearly in isostatic equilibrium. These geophysical results and additional geological investigations imply a combination of subcrustal and minor surface erosion associated with relatively small vertical isostatic movements of the crust (sinking) in former highland areas. These processes caused a retreat of the highland escarpment of at least several hundred kilometers.  相似文献   

Sequential sampling to contour an uncertain function     

Daniele Veneziano  Peter K. Kitanidis 《Mathematical Geology》1982,14(5):387-404

Sampling exploration of uncertain functions to locate critical contour levels is most effective if sampling decisions are made sequentially. A simple sequential exploration strategy, based on pseudo-Bayesian second-moment analysis, is proposed and compared with non-sequential systematic sampling. Repeated application to functions simulated pseudorandomly from stationary random processes on the line and on the plane indicates uniform superiority of the sequential strategy. The method is particularly advantageous when the function of interest,h(X), has an uncertain trend, and in general when the random process that quantifies prior uncertainty onh(X) is highly correlated.  相似文献   

3.3 Millimeter limb brightening measurements during the 30 June 1973 total solar eclipse     

F. I. Shimabukuro  W. J. Wilson  T. T. Mori  P. L. Smith 《Solar physics》1975,40(2):359-370

Solar limb brightening measurements at a wavelength of 3.3 mm were made during the 30 June 1973 total solar eclipse from a site at Lake Rudolf, Kenya. The results show that at this wavelength there is a limb brightening of about 20%, occurring within one half arc min of the limb.  相似文献   

Comment on “Special Feature on Women”     

Peter Jackson 《The Professional geographer》1982,34(4):440-440

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REPLY TO the preceding Discussion by R. A. Young of "Cambrian Stratigraphic Nomenclature and Ground-Water Prospecting Failures on the Hualapai Plateau, Arizona"     

Peter W. Huntoon 《Ground water》1978,16(4):289-291

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