Solar Wind Statistics at 1 AU: Alfven Speed and Plasma Beta     

D. J. Mullan  C. W. Smith 《Solar physics》2006,234(2):325-338

The phenomenon of MHD wave refraction is useful in interpreting the properties of the magnetic fluctuations in certain parcels of solar wind. In the physics of MHD wave refraction, variations in the Alfvén speed V_Alf play a dominant role. Here, we compile statistics of the 1-min averages of V_Alf at the location of the ACE spacecraft during its first 5 years of operation. We find that monthly distributions of V_Alf are close to log-normal, with standard deviations σ_V as small as 0.11 in the logarithm. Variations in the monthly mean V_Alf are correlated significantly with sunspot number. We also compile monthly distributions of the plasma β parameter. The distributions of both V_Alf and β are significantly narrower than they would be if the various solar wind parameters were statistically independent. In the T_p–V_Alf plane, we find a zone of avoidance at low V_Alf: for V_Alf ≤10 – 15 km/s, there are no samples in the 1-min data that are cooler than T_p = 10 000 – 15 000 K. This feature can be understood in the context of MHD wave refraction, although other explanations are also possible.  相似文献   

The use of echelle gratings in single-pass spectrometers     

A. D. Petford  D. E. Blackwell  B. S. Collins  P. A. Ibbetson  E. A. Mallia  G. Smith  D. Emerson 《Solar physics》1971,19(1):264-269

Tests of the performance of replicas of the latest echelle gratings are reported.  相似文献   

Atmospheric thermodynamics; geophysics and astrophysics monographs: J. V. Iribarne and W. L. Godson: Volume 6. Reidel,Dordrecht, Holland, 1973. x + 222. Dfl. 65.00     

R.C. Smith 《Planetary and Space Science》1975,23(8):1237-1238

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Maximum temperatures for radiation from plasma waves     

D. F. Smith  P. A. Sturrock 《Astrophysics and Space Science》1971,12(2):411-414

We derive upper limits to the radiation temperaturesT ^t(k) for emission near the fundamental and second harmonic of the electron plasma frequency in terms of the effective temperature for plasma wavesT ^l(k). We findT ^t(k)(c/(3)^1/2 V _e)³ T ^l(k) for emission near the fundamental which differs from the result of Melrose (1970b) by the factor in parentheses. This factor can exceed 4×10⁴ in some plasmas. The conditions under which this limit could be reached are delinated. For emission near the second harmonicT ^t(k)T ^l(k) since the absorption coefficient in this case can only be positive.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Spring Discharge in Relation to Rapid Fissure Flow     

Edward John Smith 《Ground water》1979,17(4):346-350

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Solute transport through a deforming porous medium     

Glen P. Peters  David W. Smith 《国际地质力学数值与分析法杂志》2002,26(7):683-717

Solute transport through a porous medium is typically modelled assuming the porous medium is rigid. However, many applications exist where the porous medium is deforming, including, municipal landfill liners, mine tailings dams, and land subsidence. In this paper, mass balance laws are used to derive the flow and transport equations for a deforming porous medium. The equations are derived in both spatial and material co‐ordinate systems. Solute transport through an engineered landfill liner is used as an illustrative example to show the differences between the theory for a rigid porous medium, and small and large deformation analysis of a deforming porous medium. It is found that the large deformation model produces shorter solute breakthrough times, followed by the small deformation model, and then the rigid porous medium model. It is also found that it is important to include spatial and temporal void ratio variations in the large deformation analysis. It is shown that a non‐linear large deformation model may greatly reduce the solute breakthrough time, compared to a standard transport analysis typically employed by environmental engineers. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Rapid neutral–neutral reactions at low temperatures: a new network and first results for TMC-1     

Ian W. M. Smith  Eric Herbst  Qiang Chang 《Monthly notices of the Royal Astronomical Society》2004,350(1):323-330

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A material model for inelastic rock deformation with spatial variation of pore pressure     

M. B. Smith  P. D. Pattillo 《国际地质力学数值与分析法杂志》1983,7(4):457-468

This paper sets forth the theoretical background and basic numerical expressions for the incorporation of elastic-plastic constitutive equations for ductile rock into a finite element computer code. The derivation of an expression for the total strain rate is performed both for a total stress formulation and for a formulation that employs the concept of effective stress for inelastic behaviour. Specific expressions for the incremental strain rate are presented for the case of a porous material having a quadratic initial yield surface and observing the associated flow rule with a special hardening law for subsequent plastic deformation. A final section of the paper summarizes the expressions required to insert the quadratic yield surface model into a finite element code.  相似文献   

Evaluation of sulfate reduction at experimentally induced mixing interfaces using small-scale push–pull tests in an aquifer–wetland system     

Tara A. Kneeshaw  Jennifer T. McGuire  Erik W. Smith  Isabelle M. Cozzarelli 《Applied Geochemistry》2007,22(12):2618-2629

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Net primary productivity of forest stands in New Hampshire estimated from Landsat and MODIS satellite data     

Christopher Potter  Peggy Gross  Vanessa Genovese  Marie-Louise Smith 《Carbon balance and management》2007,2(1):1-11

Background

A simulation model that relies on satellite observations of vegetation cover from the Landsat 7 sensor and from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate net primary productivity (NPP) of forest stands at the Bartlett Experiment Forest (BEF) in the White Mountains of New Hampshire.

Results

Net primary production (NPP) predicted from the NASA-CASA model using 30-meter resolution Landsat inputs showed variations related to both vegetation cover type and elevational effects on mean air temperatures. Overall, the highest predicted NPP from the NASA-CASA model was for deciduous forest cover at low to mid-elevation locations over the landscape. Comparison of the model-predicted annual NPP to the plot-estimated values showed a significant correlation of R² = 0.5. Stepwise addition of 30-meter resolution elevation data values explained no more than 20% of the residual variation in measured NPP patterns at BEF. Both the Landsat 7 and the 250-meter resolution MODIS derived mean annual NPP predictions for the BEF plot locations were within ± 2.5% of the mean of plot estimates for annual NPP.

Conclusion

Although MODIS imagery cannot capture the spatial details of NPP across the network of closely spaced plot locations as well as Landsat, the MODIS satellite data as inputs to the NASA-CASA model does accurately predict the average annual productivity of a site like the BEF.  相似文献