The relativistic quasilinear theory of particle acceleration by hydromagnetic turbulence     

Russell M. Kulsrud  Attilio Ferrari 《Astrophysics and Space Science》1971,12(2):302-318

The quasilinear theory of acceleration of relativistic particles by hydromagnetic turbulence is treated in the adiabatic limit of small gyration radius. The theory is based on the relativistic Vlasov equation; however, a given pitch-angle scattering rate by microturbulence is postulated and is added to this equation. The resulting acceleration is found to be given by a diffusion coefficient in total momentum, which is proportional to the spectrum of turbulence with a rate coefficient . is a frequency that represents the efficiency of each wave component of the turbulence in producing acceleration. It is given as an integral over the solution of a differential equation in pitch angle. is evaluated in various limiting cases and is shown to lead to familiar forms of acceleration, such as Fermi acceleration and magnetic pumping. Thus, a comprehensive theory of these forms of heating is achieved.  相似文献   

Natural and artificial connections between atoll islets in the pacific,their process and environmental impact     

Russell Howorth 《中国海洋大学学报(英文版)》2003,2(2):195-200

Three types of natural connection between atoll islets are described. Causeway, as an artificial way of connecting islets, makes a connection to be completed in a few months. In this case shore adjustment becomes more vigorous than that in natural conditions, resulting in lagoon shore erosion. A causeway without short bridges or culverts should be built close to the lagoon shore to reduce lagoon shore erosion. A causeway-crossing channel assemblage is the worst type among all of the connection engineering constructions because the crossing channel traps sediment and further transports it out of the channel, resulting in long period coastal erosion. Reforming Nippon Causeway in Tarawa Atoll, Kiribati by simple means will stop sand loss, reduce shore erosion and greatly upgrade its stability.  相似文献   

Contaminant concentrations in sport fish from San Francisco Bay, 1997     

Davis JA  May MD  Greenfield BK  Fairey R  Roberts C  Ichikawa G  Stoelting MS  Becker JS  Tjeerdema RS 《Marine pollution bulletin》2002,44(10):1117-1129

In 1997, seven sport fish species were sampled from seven popular fishing areas in San Francisco Bay. Mercury exceeded a human health screening value in 44 of 84 (52%) samples. All collected samples of leopard shark and striped bass exceeded the mercury screening value of 0.23 microg/g wet weight. PCBs exceeded the screening value in 51 of 72 (71%) samples. DDT, chlordane, and dieldrin, had lower numbers of samples above screening values: 16 of 72 (22%) for DDT, 11 of 72 (15%) for chlordanes, and 27 of 72 (37%) for dieldrin. Concentrations of PCBs and other trace organics were highest in white croaker and shiner surfperch, the two species with the highest fat content in their muscle tissue. Fish from one location, Oakland Harbor, had significantly elevated wet weight concentrations of mercury, PCBs, DDTs, and chlordanes compared to other locations. Removal of skin from white croaker fillets reduced lipid concentrations by 27-49% and concentrations of trace organics by 33-40%.  相似文献   

Short-Period Waves That Heat the Corona Detected at the 1999 Eclipse     

Pasachoff  Jay M.  Babcock  Bryce A.  Russell  Kevin D.  Seaton  Daniel B. 《Solar physics》2002,207(2):241-257

As a part of a study of the cause of solar coronal heating, we searched for high-frequency (1 Hz) intensity oscillations in coronal loops in the [Fexiv] coronal green line. We summarize results from observations made at the 11 August 1999 total solar eclipse from Râmnicu-Vâlcea, Romania, through clear skies. We discuss the image reduction and analysis through two simultaneous series of coronal CCD images digitized at 10 Hz for a total time of about 140 s. One series of images was taken through a 3.6 Å filter isolating the 5303 Å[Fexiv] coronal green line and the other through a 100 Å filter in the nearby K-corona continuum. Previous observations, described in Pasachoff et al. (2000), showed no evidence for oscillations in the [Fexiv] green line at a level greater than 2% of coronal intensity. We describe several improvements made over the 1998 eclipse that led to increased image clarity and sensitivity. The corona was brighter in 1999 with the solar maximum, further improving the data. We use Fourier analysis to search in the [Fexiv] channel for intensity oscillations in loops at the base of the corona. Such oscillations in the 1-Hz range are predicted as a result of density fluctuations from the resonant absorption of MHD waves. The dissipation of a significant amount of mechanical energy from the photosphere into the corona through this mechanism could provide sufficient energy to heat the corona. A Monte Carlo model of the data suggests the presence of enhanced power, particularly in the 0.75–1.0 Hz range, and we conclude that MHD waves remain a viable method for coronal heating.  相似文献   

Spatial and temporal variability and drivers of net ecosystem metabolism in western Gulf of Mexico estuaries     

Marc J. Russell  Paul A. Montagna 《Estuaries and Coasts》2007,30(1):137-153

Net ecosystem metabolism (NEM) is becoming a commonly used ecological indicator of estuarine ecosystem metabolic rates. Estuarine ecosystem processes are spatially and temporally variable, but the corresponding variability in NEM has not been properly assessed. Spatial and temporal variability in NEM was assessed in four western Gulf of Mexico shallow water estuaries. NEM was calculated from high-frequency dissolved oxygen measurements. Interbay, intrabay, and water column spatial scales were assessed for NEM, gross primary production (GPP), and respiration (R) rate variability. Seasonal, monthly, and daily temporal scales in NEM, GPP, and R were also assessed. Environmental conditions were then compared to NEM to determine which factors were correlated with each temporal and spatial scale. There was significant NEM spatial variability on interbay, intrabay, and water column spatial scales. Significant spatial variability was ephemeral, so it was difficult to ascertain which environmental conditions were most influential at each spatial scale. Significant temporal variability in NEM on seasonal, monthly, and daily scales was found and it was correlated to temperature, salinity, and freshwater inflow, respectively. NEM correlated strongly with dissolved oxygen, temperature, and salinity, but the relationships where different in each bay. The dynamics of NEM on daily scales indicate that freshwater inflow events may be the main driver of NEM in the semiarid estuaries studied. The variable nature of NEM found here is further evidence that it is not valid to use single station monitoring deployments for assessment of whole estuarine ecosystem metabolic rates in large ecosystems. The relationship between NEM and temperature, salinity, and freshwater inflow events could drive predictive models assessing the potential influence of projected climate change and watershed development scenarios on estuarine metabolic rates.  相似文献   

Chemical ozone loss in the Arctic vortex in the winter 1995–96: HALOE measurements in conjunction with other observations     

R. Müller  J.-U. Grooß  D. S. McKenna  P. J. Crutzen  C. Brühl  J. M. Russell III  L. L. Gordley  J. P. Burrows  A. F. Tuck 《Annales Geophysicae》1998,17(1):101-114

Severe chemical ozone loss has been detected in the Arctic in the winter and spring of 1995–96 by a variety of methods. Extreme reductions in column ozone due to halogen catalysed chemistry were derived from measurements of the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite in the Arctic vortex. Here, we discuss further aspects of the HALOE observations in the Arctic over this period. Potential problems, both in the data themselves and in the methodology of the data analysis are considered and the reason for the differences between the Arctic ozone losses deduced from HALOE data version 17 and 18 is analysed. Moreover, it is shown that HALOE measurements in the Arctic in winter and spring 1995–96 compare well with observations by other ground-based and satellite instruments.  相似文献   

The ortho- to para- ratio of H₂ in the starburst of NGC 253     

Andrew Harrison  Phil Puxley  Adrian Russell  & Peter Brand 《Monthly notices of the Royal Astronomical Society》1998,297(2):624-632

We present measurements of several near-infrared emission lines from the nearby galaxy NGC 253. We have been able to measure four H₂ lines across the circumnuclear starburst, from which we estimate the ortho- to para- ratio of excited H₂ to be ∼2. This indicates that the bulk of the H₂ emission arises from photodissociation regions (PDRs), rather than from shocks. This is the case across the entire region of active star formation.
As the H₂ emission arises from PDRs, it is likely that the ratio of H₂ to Brγ (the bright hydrogen recombination line) is a measure of the relative geometry of O and B stars and PDRs. Towards the nucleus of NGC 253 the geometry is deduced to be tightly clustered O and B stars in a few giant H  II regions that are encompassed by PDRs. Away from the nuclear region, the geometry becomes that of PDRs bathed in a relatively diffuse ultraviolet radiation field.
The rotation curves of 1–0 S(1) and Brγ suggest that the ionized gas is tracing a kinetic system different from that of the molecular gas in NGC 253, particularly away from the nucleus.  相似文献   

Ca isotope fractionation on the Earth and other solar system materials   总被引：1，自引：0，他引：1  

W.A. Russell  D.A. Papanastassiou  T.A. Tombrello 《Geochimica et cosmochimica acta》1978,42(8):1075-1090

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The Martian magnetic field     

C.T. Russell 《Physics of the Earth and Planetary Interiors》1979,20(2-4):237-246

The magnetic field measurements of the Mars 2, 3 and 5 spacecraft have been interpreted by Dolginov and co-workers to be consistent with an intrinsic planetary magnetic moment of 2.5 × 10²² gauss cm³. They base this interpretation mainly on the apparent size of the obstacle responsible for deflecting the solar wind, the lack of dependence of the sign of the magnetic field in the wake region of the planet on the sign of the component of the interplanetary field radially out from the sun, and an apparent encounter of the Mars spacecraft with the planetary field. When examined in detail this evidence is very suspect. A detailed criticism of the arguments by Dolginov and co-workers for an intrinsic field has appeared elsewhere. Herein we summarize this criticism and present, in an appendix, a compendium of the Mars 3 and 5 magnetic field data transformed into a coordinate system in which the details of the interaction are more easily visualized. Many of these data have not been published in this form previously.  相似文献   

Use of clast shape in determining the sedimentary history of the late devonian keepit conglomerate,Australia     

Terry Russell 《Sedimentary Geology》1980,25(4):277-290

Clasts of the Late Devonian Keepit Conglomerate of northeastern New South Wales, Australia, are predominantly andesites of isotropic nature that lack any apparent initial shape controls. Given adequate time in a particular environment, these clasts could be reasonably expected to develop shapes characteristic of abrasion within that environment.Clasts from both fluvial and marine resedimented conglomerates of the Keepit Conglomerate possess shape characteristics indicative of shaping within a fluvial environment. Maximum projection sphericity, and a plot of sphericity against either the oblate-prolate index or the flatness parameter C/A, were the most useful in indicating fluvial shaping processes. In addition, the $\text{OP}$ Index and the dominant form classes of the Sneed and Folk Sphericity-Form diagram were in support of a fluvial history for the clasts.The occurrence of clasts exhibiting typical fluvial shapes in marine resedimented conglomerates indicates a lack of time and/or insufficient energy in a beach environment for reshaping of the clasts prior to resedimentation into deeper-water submarine-fan environments. This interpretation is consistent with and lends support to the interpretation, based on all other available data, for the Keepit Conglomerate of a history of rapid progradation of fluvial gravels into a relatively low-energy coastline environment, with periodic resedimentation of coarse sediment into deeper water.  相似文献