The sources of large-scale heliospheric disturbances     

A. Hewish  S. Bravo 《Solar physics》1986,106(1):185-200

Observations on a grid of 900 radio sources have been used to map and to track large-scale structures in the solar wind at distances of 0.6–1.5 AU from the Sun. Most of the disturbances were shells of enhanced density followed by high-speed streams lasting for several days, although more stable corotating interaction regions were also observed. Ninety-six disturbances were mapped during August 1978–September 1979 and those of the erupting stream-type were usually accompanied by shocks and geomagnetic activity if they encountered the Earth. Back-projection to the Sun indicated sources that were always associated with coronal holes. Possible associations with solar flares and disappearing filaments occurred but on many occasions no flare or filament activity was evident anywhere on the disc within a suitable time interval. It is concluded that erupting streams are transients generated by coronal hole activity. Evidence is presented which further suggests that coronal mass ejections of the curved-front variety may be identified with these erupting streams.  相似文献   

A Nonlinear Model of Surf Beat     

Nicholas Dodd 《中国海洋工程》1995,(2)

A nonlinear short-wave-averaged (surf beat) model is presented. The model is based on that of Roelvink (1993), but the numerical techniques used in the solution are based on the so-called weighted-averaged flux (WAF) method (eg Watson et al., 1992), with time-operator splitting used for the treatment of some of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modelling breaking long waves. The short-wave (or primary-wave) energy equation is solved using a more traditional Lax-Wendroff technique. Results of validation indicate that the model performs satisfactorily in most respects.  相似文献   

Solar flare activity and the structure of the coronal neutral line     

G. A. Stewart  S. Bravo 《Solar physics》1995,160(2):331-341

In this study we analyse the positions of major flares from 1978 and 1979, with respect to the magnetic structure of the solar corona, as described by a potential field model. We find that major flares exhibit no strong association with the neutral line at the chromospheric level. However, when we calculate the neutral line's position at higher and higher altitudes in the corona, we find that major flares show an increasing tendency to be found close to these high-altitude coronal neutral lines. The correlation between flares and higher-altitude coronal neutral lines reaches a maximum at an altitude of 0.35R , and thereafter decreases as the neutral line is moved out to the source surface at an altitude of 1.50R . This indicates that major flares are strongly associated with coronal structure at the 0.35R level ( 250 000 km) - an altitude surprisingly high in the corona. This reinforces the idea that flares are associated with large-scale coronal magnetic fields and also indicates that the region of coronal magnetic topology important to solar flare processes may be larger than previously thought.  相似文献   

Nucleosynthesis in SNIa     

E. Bravo  J. Isern  R. Canal  J. Labay 《Astrophysics and Space Science》1990,169(1-2):19-24

The final products of a SNIa explosion critically depend on the degree of neutronization of the incinerated material and on the total amount of burned material. Here we study their dependence on the velocity of the burning front and on the density at which the thermonuclear runaway starts. The abundances of⁵⁴Cr,^{54, 58}Fe,^{58, 62}Ni provide some constraints to the possible values of model parameters.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

Particulate air pollution from wildfires in the Western US under climate change     

Jia Coco Liu  Loretta J. Mickley  Melissa P. Sulprizio  Francesca Dominici  Xu Yue  Keita Ebisu  Georgiana Brooke Anderson  Rafi F. A. Khan  Mercedes A. Bravo  Michelle L. Bell 《Climatic change》2016,135(3-4):655-668

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白云鄂博碳酸岩墙的稀土和微量元素地球化学及对其成因的启示   总被引：11，自引：1，他引：11  

王凯怡  范宏瑞等 《岩石学报》2002,18(3):340-348

根据矿物组成白云鄂博矿区的碳酸岩岩可墙可分为白云石型、白云石－方解石共存型和方解石型三种类型。REE和微量元素地球化学表明，这三类碳酸岩岩墙为碳酸岩浆演化不同阶段的产物，白云石型和白云石－方解石共存型对应于早期岩浆阶段，其（La/Nd)n、(La/Yb)n比值随稀土总量的增加而增大，方解石型则对应于碳酸岩浆演化的晚期热液阶段，其稀土总量明显富集，但其（La/Nd)n、(La/Y)n和（La/Yb)n比值随稀土总量的增加却有减小的趋势，热液阶段也是白云鄂博稀土矿化的主要阶段。  相似文献   

Glacier development and topographic context     

J. I. Lpez‐Moreno  D. Nogus‐Bravo  J. Chueca‐Cía  A. Julin‐Andrs 《地球表面变化过程与地形》2006,31(12):1585-1594

This paper analyses the topographic context of the remaining glaciated areas in the Maladeta Massif (Central Spanish Pyrenees). These ice‐covered surfaces have been incorporated into a geographic information system (GIS) in an attempt at correlating the presence of ice with a range of topographic variables obtained from a digital elevation model. The use of generalized additive models and binary regression tree models enabled us (i) to quantify the spatial variability in the distribution of glaciers attributable to characteristics of the local terrain, (ii) to investigate the interaction between the variables that account for the ice cover distribution and (iii) to map the probability of glacier development. Our results show that although the development of glaciers depends on regional climate conditions, the topographic context is of paramount importance in determining the location, extent, shape and recent evolution of each glacial body. Thus, the joint effect of altitude, exposure to incoming solar radiation, slope and mean curvature is able to explain more than 70 per cent of the observed variance. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The Varying Multipolar Structure of the Sun's Magnetic Field and the Evolution of the Solar Magnetosphere Through the Solar Cycle     

Bravo  S.  Stewart  G. A.  Blanco-Cano  X. 《Solar physics》1998,179(2):223-235

The Sun's magnetic field extends far from the photosphere, into the corona, defining a magnetically dominated region before being drawn out radially by the solar wind flow. This region, where the internal sources of the solar field dominate the plasma structures and the energetic particle movement, can be properly considered the solar magnetosphere. The magnetic field in this region can be approximately described by models that extrapolate photospheric magnetic field observations under some simplifying assumptions. In this paper we use a potential field model which describes the solar field up to a source surface at 3.25 R_s, where the field is constrained to become radial. We present the variation of the magnitude and inclination of the various multipolar components throughout the solar magnetic cycle that characterise the changes in the structure of the solar magnetosphere over a period of 22 years. We also present some 3-D images of the coronal magnetic structure to show the global evolution of the solar magnetosphere throughout the solar cycle and discuss the importance of taking this structure into account in order to relate interplanetary and solar features.  相似文献   

Signatures of interplanetary transients behind shocks and their associated near-surface solar activity     

S. Bravo  X. Blanco-Cano 《Annales Geophysicae》1998,16(4):359-369

Interplanetary transients with particular signatures different from the normal solar wind have been observed behind interplanetary shocks and also without shocks. In this paper we have selected four well-known transient interplanetary signatures, namely: magnetic clouds, helium enhancements and bidirectional electron and ion fluxes, found in the solar wind behind shocks, and undertaken a correlative study between them and the corresponding solar observations. We found that although commonly different signatures appear in a single interplanetary transient event, they are not necessarily simultaneous, that is, they may belong to different plasma regions within the ejecta, which suggests that they may be generated by complex processes involving the ejection of plasma from different solar regions. We also found that more than 90% of these signatures correspond to cases when an H flare and the eruption of a filament occurred near solar central meridian between 1 and 4 days before the observation of the disturbance at 1 AU, the highest association being with flares taking place between 2 and 3 days before. The majority of the H flares were also accompanied by soft X-ray events. We also studied the longitudinal distribution of the associated solar events and found that between 80% and 90% of the interplanetary ejecta were associated with solar events within a longitudinal band of ±30° from the solar central meridian. An east-west asymmetry in the associated solar events seems to exist for some of the signatures. We also look for coronal holes adjacent to the site of the explosive event and find that they were present almost in every case.  相似文献   

Internationaler Workshop aktiver Phytoplanktologen 21. bis 27. August 1978 in Kastanienbaum     

HR. Bürgi 《Aquatic Sciences - Research Across Boundaries》1978,40(2):306-309

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