Approximations to the plasma refractive index

For fifty years the quasi-longitudinal and quasi-transverse approximations to the refractive index formula for an ionised plasma have been used. Recent investigations have sought to generalise the traditional treatment in various ways. In the author's opinion, something further remains to be explained, and in the present paper various algebraic identities are examined between distinct forms of the refractive index, whereby a radical can sometimes be switched between numerator and denominator. Approximations to this radical are kept distinct algebraically from any subsequent expansions that may be made in the refractive index formula. The properties of this radical and its various approximations are examined in detail, both algebraically and numerically.     

Determination of the atmospheric refractive index structure parameter from refractivity measurements and amplitude scintillation measurements at 36 GHz

Results are presented of the determination of the atmospheric refractive index structure parameter C_n², deduced from amplitude scintillation measurements made on a 36 GHz radio link and also from the refractive index frequency spectrum computed from refractivity measurements using a radio refractometer. The two methods of measurement give acceptable agreement and provide further experimental evidence of the applicability of Tatarski's wave propagation theory in a turbulent medium to millimetre wavelengths.     

The influence of high speed plasma streams on the ionospheric plasma

As shown by statistical investigations, high speed plasma streams (HSPS) in the solar wind cause direct ionospheric effects in the D- and Es-layers at auroral and subauroral latitudes due to increasing precipitation of high energetic particles as well as indirect effects in the F2-region at high, middle and equatorial latitudes caused by auroral heating processes. The ionospheric effects increase with the strength of the HSPS and are most pronounced for HSPS during IMF pro sectors (sectors with negative B_z-component). Seasonal differences of the ionospheric response to solar velocity changes are caused by the IMF influence (maximum effect at equinoxes) as well as internal atmospheric reasons (enhanced variability during winter).     

The diffusion of the plasma column inclined at an angle to the magnetic field

Using a two-dimensional model a study is made of the dynamics of plasma irregularities, embedded in a weakly covered plasma, containing an electric field transverse to the magnetic field. The analysis shows that due to field aligned and Hall plasma drift, the irregularities are divided into two parts, one of which is stretched along the magnetic field.     

Application of refractive scintillation theory to radio transmission through the ionosphere and the solar wind,and to reflection from a rough ocean

The results of Booker and Majidiahi (1981) concerning refractive scattering by large-scale irregularities in a phase-changing screen are combined with the theory of diffractive scattering by small-scale irregularities in order to study three intensity scintillation phenomena. The first is the reflection of radio and optical waves from an ocean surface disturbed by a spectrum of water waves. The second is the scintillation of VHP, UHF and SHF radio waves traversing the ionospheric F-region. The third is the scintillation of VHF, UHF and SHF radio waves traversing the solar wind. In each case appropriate values are chosen for the mean square fluctuation of phase, for the outer scale, for the inner scale and for the spectral index. Spectral diagrams are drawn to show how the outer scale, the inner scale, the Fresnel scale, the focal scale, the lens scale and the peak scale vary with a relevant parameter (electromagnetic wave-frequency for the ocean, RMS fractional fluctuation of ionization density for the ionosphere, and distance of closest approach to the Sun for the solar wind). For the ionosphere and the solar wind, multiple refractive scattering by weak irregularities occurs in practice whereas it is strong single scattering that is assumed in the thin-screen theory ; potential consequences of this are discussed qualitatively.     

考古木材降解评价的物理指标

为寻找一种能较为科学、方便地反映木材降解程度的指标,共收集不同地方出土的13种木材,8个树种,对这些树种的考古木材与新鲜木材的含水率、干缩性、基本密度、气干密度、综纤维素等指标进行对比分析。实验表明,基本密度和最大含水率(饱水含水率)基本上能够反映古木的降解程度,可以作为反映古木降解程度的物理评价指标。     

Inequality and the return to structure in anthropology

The four books under review are all more or less explicitly critical of the impact of post-modernism on socio-cultural anthropology and archaeology. They all call for the building of anthropology by reconnecting to the earlier traditions of structural and comparative analysis. Although spanning both socio-cultural anthropology and archaeology, they set the focus clearly on the pervasive influence of inequality on social processes. The different authors demonstrate the explanatory power of concepts such as class, surplus, inequality, and structure for a multitude of contexts from prehistoric foragers to neo-liberal market ideologies.     

Non-relativistic and relativistic approaches to the problem of plasma wave propagation

When using the approximate expression for different wave refractive indices derived by Sazhin we outlined those values of plasma parameters and wave frequencies for which cold and non-relativistic plasma approximations are valid. For R and O waves the latter approximation is valid when the wave frequency is close to the electron gyrofrequency; for the X wave it is valid when the wave frequency is close to the doubled electron gyrofrequency.     

A comparison of plasma densities by EISCAT and the Dynasonde from auroral altitudes: evidence of intense structure

Under conditions of moderately-energetic particle precipitation typical of the equatorward side of the auroral oval, plasma densities obtained from routine analysis of EISCAT Common Program data are often a factor 2 to 5 smaller than those suggested by co-located digital ionograms. We consider the reasons for this disagreement, and in particular we reject the implications of diffractive and multiplyrefractive scatter as alternatives to the usual plasma-frequency interpretation of ionogram echoes. We examine the effects of the (5 min and shorter) temporal averaging applied to the EISCAT data and conclude that together with the evidently small size (perhaps as little as 20 km) and high velocity of these structures, this accounts for much, if not all, of the disagreement. We point out the significance of the higher plasma densities in the 100–150 km height range for estimates of Joule and particle heating.     

The Neronian and the historical structure of cultural shifts from Middle to Upper Palaeolithic in Mediterranean France

The end of the Middle Palaeolithic period can be considered a key moment in the history of humanity, characterized by profound changes in traditional Palaeolithic societies. Whatever the reasons for this historical change, it seems well established that it took place within a particularly dynamic phase of these societies, when Upper Palaeolithic technical processes were already emerging. The analysis of recent Mousterian industries in Mediterranean France highlights certain points of inflection, which presage new ways of life. The analysis of key sites demonstrates important transformations within the last Neanderthal societies, with a gradual rearticulation of Mousterian technical systems around the production of blades and points and with profound changes in the relationship of the craftsman with his tools. Even if they are typical of the late Mousterian more generally, these technically distinctive industries have such distinct chronological, territorial and cultural characteristics that they can be referred to by a specific name, the “Néronien” (Neronian). Stratigraphically speaking, this group of assemblages – at the crossroads of the Middle and Upper Palaeolithic – appears in some important regional sequences just before the appearance of the first “true” Upper Palaeolithic industries (the Protoaurignacian). However, this Neronian doesn't represent the end of the Middle Palaeolithic period in the Rhône valley. The final Moustérien of this region is actually marked by deep breakdowns of the traditional balances in the human groups. This second point of inflection could characterize a true destabilization of Mousterian societies. There is an interesting parallelism between the historical paths of the Castelperronian in the arch of the Massif Central and the Neronian in the Rhône valley. It also highlights the mosaic nature of the profound cultural changes that occurred at the end of the Middle Palaeolithic.     

Erratum to: Analyzing and dating the structure of the Phaistos Disk

This paper offers an analysis and dating of the structure of the “Phaistos Disk”, made from clay, imprinted with undeciphered symbols, grouped in roughly 30 boxes per disk side, and found in the ruins of the Phaistos Palace on the Greek Island of Crete by Luigi Pernier in 1908. The author suggests that the disk side A containing a petal in the center box shows astronomical eclipse information, which belong to a complete Saros cycle beginning −1377 and valid for the Phaistos Palace location only.     

A model of ionospheric image structure underneath a braking,cross-field plasma jet

A plasma jetting across the geomagnetic field above the ionosphere tends to brake by ohmic dissipation of Pedersen currents. The braking can affect the ionosphere underneath if the associated Pedersen drifts are intense and prolonged enough to cause cumulative image structuring. We examine such image structuring for the parameter regime of forthcoming CRRES releases, involving photo-ionization of kilograms of barium vapor moving at orbital velocity. The resultant structuring in the upper E-region offers possible diagnostic tell-tales of the braking process.     

试论团练大臣与双重统治格周

团练大臣是19世纪中期中国传统双重统治格局受到重大挑战和清廷调整统治结构、重建统治秩序过程中的产物.团练大臣在有清二百余年中只存在了十年左右,但其发端、定型、演变,以及最终被取消的过程,却反映了双重统治格局中上下层统治相互间的关联与斗争、力量对比的变化、发展的多元走向和必然趋势.本文通过对团练大臣和其时双重统治格局的研究探讨,为人们认识中国传统社会的运转方式、固有道路及发展趋势提供了一个不可多得的样板.     

Confessional cousins and the rest: The structure of Islamic toleration

This article is an expanded version of a paper given on 22 November 2003 in a session of the American Anthropological Association Annual Meetings in Chicago, organized by Vinson Sutlive in honour of George and Laura Appell, entitled 'Human rights and cultural preservation in the interest of peace'. I am grateful to the RAI for inviting me to represent it at the AAA meeting, to Jean La Fontaine for her comments on an earlier draft, and to a number of extremely helpful anonymous referees.

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  Another historical example may be the pagan Vikings who appeared on the Spanish and Moroccan coasts in the ninth century and were called Mājūs , that is Magians or Zoroastrians, not because they were thought to be Persians but because as a people recognized by law they did not have to be fought, and were eligible for a truce for the purposes of trade (Brunschvig 1986, Brett and Fentress 1996). However, this is disputed (Melvinger 1986).

       
  
  

The body mass index of blacks and whites in the United States during the nineteenth century

Body mass index (BMI) values reflect the net balance between nutrition, work effort, and calories consumed to fight disease. Nineteenth-century prison records in the United States demonstrate that the BMI values of blacks and whites were distributed symmetrically; neither underweight nor obese individuals were common among the working class. BMI values declined throughout the nineteenth century. By modern standards, however, nineteenth-century BMIs were in healthy weight ranges, though the biological living standards in rural areas exceeded those in urban areas. The increase in BMIs during the twentieth century did not have its origin in the nineteenth century.     

The influence of ionization and recombination processes on the dynamics of ionospheric plasma clouds

The dynamics of a one-dimensional ionospheric irregularity interacting with the magnetosphere is studied by numerical simulation. The polarization electric field produced by charge separation within the irregularity propagates along magnetic field lines with the Alfvén velocity V_A and drives polarizational and field-aligned currents in the magnetosphere. Their values and localization are controlled by motion and deformation of the irregularity resulting from its electrostatic coupling to the background ionosphere. The pattern of the field-aligned currents varies with time and depends primarily on gradients of the polarization electric field. The latter is controlled by the ambient electric field, diffusion, recombination process, intensity of the initial perturbation, etc. Feedback effect of the magnetospheric conductance on the development of the irregularity is examined.