Quasi-periodic particle precipitation and Trimpi activity at Halley,Antarctica

The relationship between quasi-periodic VLF emissions and micropulsations is briefly reviewed, and then discussed with reference to an event recorded at Halley, Antarctica, on day 257 in 1986. VLF emissions at 2 kHz with a quasi-period of 9 s were observed simultaneously with Pi1 and Pe1 micropulsations. Also observed was a quasi-periodic Trimpi event on the amplitudes and phases of the VLF transmitters NAA and NSS. It is deduced that the VLF emissions are modulated in the generation region by a hydromagnetic wave, giving rise to particle precipitation. The emissions are also modulated by the bounce period of the generating particles. The Trimpi effect is due to 120 keV electrons being precipitated into the lower ionosphere by the interaction with the VLF emissions. This event shows that the Trimpi effect can be used to detect particle precipitation occurring during the ULF/VLF interaction, and can give information which helps to define the mechanism reponsible for the interaction.     

The effect of Birkeland currents on the growth rate of VLF emissions

VLF emissions produced by a gyro-resonant interaction in the presence of a bi-Maxwellian plasma penetrated by a current have been studied. The results obtained show that field-aligned currents reduce the growth rate due to temperature anisotropy. This phenomenon is analysed theoretically to assess the effect of Birkeland currents on very low frequency (VLF) emissions occurring in the magnetosphere.     

Periodic and quasiperiodic VLF emissions

A review of periodic and quasiperiodic VLF emissions observed at ground-based stations and in the Earth's magnetosphere is presented. Emissions with periods below 10 s are divided into three main groups: periodic emissions, hisslers and pulsing hiss, while the quasiperiodic emissions with periods above 10 s are divided into two main groups: QP1, which are definitely related to geomagnetic pulsations, and QP2, which are not obviously related to them, based on ground observations. However, it is pointed out that all types of quasiperiodic emissions with periods over 10 s observed onboard satellites show some association with geomagnetic pulsations which suggests that both QP1 and QP2 can have similar mechanisms for their generation. Different approaches to the theoretical modelling of periodic and quasiperiodic emissions are discussed.     

Controlled electron beam experiments in space and supporting laboratory experiments: a review

The injection of energetic charged-particle beams in space represents an exciting area for controlled experiments in the Earth's ionosphere and magnetosphere. Under the influence of a multitude of controlling parameters, a mono-energetic charged-particle beam might follow a well-defined singleparticle trajectory or it might undergo collective beam-plasma effects that substantially modify its energy and density distributions. In the latter case, one finds a multitude of possibilities for unstable plasma modes. If on the other hand the beam maintains single-particle characteristics, it can be a useful diagnostic tool for such applications as geomagnetic conjugate mapping and measurement of magneticfield-aligned potentials. The evolution of these concepts, along with the developing technology of spaceborne charged-particle beam accelerators, has ushered in an area of basic plasma and geoplasma physics previously not available to the scientific community. Over the past five years this activity has brought about important improvements in our fundamental understanding of beams and beam plasma processes. This progress has been brought about not by space experiments alone, but by the synergistic efforts of computational physicists, and the exchange of ideas born from laboratory simulations of space plasma processes involving energetic particle beams. It is the aim of this review paper to develop a synoptic perspective on recent accomplishments, and to summarize plans and recommendations for future experiments which will contribute to continued growth in the field.     

Perspectives of present and future space weather forecasts

Two main targets of space weather forecasts are to, predict solar energetic particles (SEPs) produced by flares and coronal mass ejections CMEs), and the energetic particles or hot plasma injected into the inner magnetosphere during magnetic storms and substorms. For the purpose of constructing models to predict these particle popuplations, we critically review the problems in flares and CMEs, and the problems in magnetic and substorms For flares and CMEs, we point out the importance of distinguishing the effects of flares from the effects of CMEs, because it seems that many physical processes operate commonlyto both phenomena and produce similar effects. Recent studies on SEP events have shown that advanced measurements of SEPs can distinguish between these two acceleration sources. We propose a possible relationship between flare and CMEs based on an idea of dual magnetic field structures of different characteristic scales. It is expected that further progress can be accomplished by vector magnetographs, sold X-ray telescopes, and advanced measurements of solar wind composition as well as SEP composition. Far magnetic storms and substorms, it is found that analysis by the linear filtering technique can give results which are very consistent with theoretical understanding. Therefore, it is strongly recognized that the next step should be fully theoretical studies, or simulations.     

国内外城中村研究进展及展望

从国内和国外两条线回顾城中村相关研究进展。在国内研究综述方面,分别从对城中村现象的认识、城中村形成机制、城中村改造及发展建议三个方面概括各阶段学术界对城中村问题的研究成果;而在国外研究综述方面,按照自助型居住区研究、城中村流动人口居住研究、及城中村土地利用研究三个主题进行文献综述。通过回顾现有研究成果,指出基于城市地理学理论的城中村研究,在理论支撑方面需建立明确和多样的理论体系,在研究内容方面应选择更深层次的议题,在研究方法方面应加强定量研究方法的应用。     

Middle atmosphere tides

Recent progress in the study of middle atmosphere tides is reviewed. Specific areas where recent progress has occurred include: development of more realistic thermal excitation and numerical simulation models; the role of tides in accelerating and heating the mean flow at the base of the thermosphere; observational efforts which delineate average seasonal, latitudinal and vertical structures of tides, and shorterterm variations of tides about these values; theoretical and observational studies concerning the importance of non-migrating tidal components; the effects of tides on minor constituent concentrations in the upper mesosphere and lower thermosphere. The review concludes with a summary of key problems to be addressed in the future.     

Children's Understanding of Aerial Photographs

As aerial photographs are widely used in geography education, it is important to know how children's understanding of these representations develops through the school years. We review research that has addressed children's understanding of the content of aerial photographs, and we describe a series of studies in which children used information from aerial photographs to carry out spatial tasks in a large space. We demonstrate that using an aerial photograph can be an aid to subsequently using a map, and we discuss the educational applications of the research with aerial photographs.     

MISREPRESENTING MARX: A LESSON IN HISTORICAL METHOD

In this book Jonathan Sperber deploys his extensive knowledge of nineteenth‐century European social and political history, and his diligent research into sources that have become readily available only recently, to produce a substantial biography of Karl Marx. We find, however, that Sperber is mistaken in his treatment of Marx's ideas and of the intellectual contexts within which Marx worked. In fact, we suggest that he is systematically mistaken in this regard. We locate a root source of the error in his reductive approach to theoretical ideas. In section I we focus on the claim, taken for granted in the book, that Marx's ideas are instantiations of “materialism.” By detailed reference to the record of Marx's writings, we show that there is no justification for describing Marx as a “materialist” in the usually accepted senses of that term. In section II we review how Soviet and other interpreters of Marx, taking their lead from the later Engels, insisted that “materialism” was fundamental to Marxism. We suggest that Sperber's presentation of Marx's thinking as “materialist and atheist” aligns far better with such interpretations than it does with what Marx actually wrote. In sections III and IV we criticize Sperber's “contextualist” approach to dealing with ideas in history. His approach may seem reminiscent of Quentin Skinner’ s, but where Skinner deploys the discursive conventions prevailing in a past time to illuminate theoretical ideas, Sperber reduces theoretical ideas to context. We name Sperber's approach “theoretical nominalism,” a term that we use to denote the view that theoretical ideas are nothing but interventions into particular situations. We end by suggesting that greater attentiveness to philosophy and theory would have enriched Sperber's efforts in this book.     

Introduction to the special issue on numerical modeling of hydrothermal fluids

This special issue on the numerical modeling of hydrothermal fluids is an outgrowth of a thematic session convened at the 2007 Geological Society of America meeting in Denver. Here we briefly review some of the previous research into numerical modeling of hydrothermal fluids and summarize the contributions in this special issue. We find that despite decades of progress, there is still great untapped potential for providing insights into the behavior of hydrothermal fluids by numerical modeling.     

Radio noise of auroral origin: 1968–1988

There have been various reports of radio noise from the aurora dating back to 1946. Here we review radio waves in the frequency range 0.1–200 MHz; not included is the extensive literature on auroral hiss, which typically occurs at lower frequencies, and on auroral kilometric radiation, which is not observable from the ground. A previous review appeared in 1969 and covered the period 1946–1967; in this review we concentrate on the observations between 1968 and 1988. In addition to ground-based observations, relevant in situ observations and theoretical advances are discussed. More experimental work is needed to determine whether all of the observations represent auroral phenomena, to identify and classify the observed emissions, and to estimate the extent to which the various existing observations represent the same phenomena. On the theoretical side, a number of mechanisms have been proposed which show some promise to explain the observed emissions, but many uncertainties remain.     

On the effect of a beam of energetic electrons on the whistler-mode growth rate due to gyroresonant interactions

The dispersion relation for whistler-mode waves in the presence of an idealised beam of energetic electrons that is moving either parallel or antiparallel to the gyroresonant electrons is analysed. The dependence of the real part of the dispersion relation on the velocity of the beam is shown to be responsible for an additional growth rate, for the beam antiparallel to the gyroresonant electrons, or for a reduced growth rate for the parallel condition. The effect could be important in explaining some features of VLF emissions such as hiss which propagate through the magnetosphere in the opposite direction to the gyroresonant electrons.     

Unintentional man-made modification effects in the magnetosphere

Evidence continues to accumulate that even very small input signals, such as power-line harmonic radiation (PLHR), can give rise to wave-particle interactions in the magnetosphere by stimulation of emission at VLF and contribute to the formation of the electron slot (2<L<3). Over North America and its geomagnetic conjugate, the satellite data indicate a permanent zone of VLF emission which appears to originate in the industrial areas of northeastern U.S.A. and southern Canada. The more intense stimulated emission in the summer (northern hemisphere) occurs poleward of the electron slot at 3<L<5. The resultant increased electron precipitation may explain the increase in thunderstorms at L>4 in the period 1935–1970 relative to 1900–1935. There is probably an intensity threshold at which PLHR becomes important. This is consistent with ground-based data from longitudinally separated stations near L = 4 (Siple, Halley, Yakutsk). The discovery that certain industrial plants (e.g. cement works) give rise to relatively much more intense PLHR requires further investigation. Also, geomagnetically induced currents in long power lines at high geomagnetic latitudes in Canada and Alaska can result in transformer saturation and possible damage, as well as greatly increased PLHR.Powerful VLF transmitters in the range 15–25 kHz can produce peaks in the spectra of energetic electrons observed on low altitude satellites. Morphological studies of the NAA wavefield intensity above the ionosphere show strong amplification immediately to the east of the South Atlantic Anomaly.     

On reductionism and emergence in geomorphology

Much geomorphological enquiry has been devoted to the understanding of landscapes via the construction of models based on the relationships between process and form. This paper examines the philosophical, theoretical and practical problems involved in bridging the gap between studies of geomorphological processes and explanations of landscape development. It argues that process geomorphology is essentially reductionist and discusses the practical and logical limitations of such an approach to science. It suggests that landscapes are emergent phenomena and, by drawing from the philosophical and practical lessons derived from the physics of non-linear systems, demonstrates that they are not amenable to reductionist explanations.     

L’impossible Incarnation D’une Monarchie Une Crise de la Régence du Dernier Habsbourg d’Espagne (1668–1669)

Through the crisis of the regency of the last Habsburg, which triggered a “conflict of legitimation”, this article analyses the notion of legitimacy from the viewpoint of the action and from the viewpoint of the ideas that underlie the action. Our investigation shows the interactionist nature of the practices of legitimation and emphasises the limit of an explanation based on rhetoric. In a conflict that cannot be equated to the mere physics of confrontations, the key question is that of the incarnation of the sociopolitical body.     

Albert Einstein,Physicist (1879–1955)

Abstract

Einstein's ideas changed man's thoughts about the totality of physics. These ideas were so fundamental for human thought that Einstein belongs to all the sciences and to all cultures. If ever there was a scientist whose centenary ought to be commemorated in an interdisciplinary journal, Einstein would be that one. This is because of the all-pervading influence of the revolution in physics in which Einstein played so paramount a part. Here we look back to what one man was able to contribute to transforming everyman's thought about the physical world. For the most part the lasting consequences are evident and well-known. Nevertheless, we have to observe that in some respect – not necessarily those emphasized by Einstein – the implications are still scarcely apprehended.     

Dayside high latitude magnetic impulsive events: their characteristics and relationship to sudden impulses

On 17 December 1990 a series magnetic impulsive events (MIEs) were observed at high latitudes near local noon. EISCAT, situated some 5 hours of MLT away from the noon sector, detected simultaneous impulsive electron density enhancements at heights between 90 and 120 km. The MIEs at noon were also associated with riometer absorption spikes. The correlated EISCAT and riometer observations indicate that there was an elongated electron precipitation region some 3000 km wide stretching from local noon to morning. In close association with the impulsive electron precipitation, VLF emissions were observed by groundbased stations in the morning side. We interpret the large scale electron precipitation and VLF emissions as signatures of a global compression of the Earth's magnetosphere. This is confirmed by the specific type of magnetic variations simultaneously recorded at the worldwide network of magnetometers. We conclude that the small scale MIEs with their drifting ionospheric current vortex structures can (but do not necessarily have to) occur in conjunction with large scale SIs. Moreover, MIEs and SIs have a common origin: the interaction of solar wind inhomogeneities with the Earth's magnetosphere. They do, however, represent different effects of the same primary agent.     

Subsoil Interventions Effect on Structural Seismic Response. Part I: Validation of Numerical Simulations

Subsoil interventions to enhance the static soil resistance and reduce deformations may alter significantly the seismic response of the complex soil-foundation-structure system. The aim of this article is to have an insight in the physics of the problems encountered and to validate an adequate numerical modeling procedure to study these effects of the intervention in the global response of the system. Validation concerns wave propagation, site effects, and dynamic soil-structure-interaction issues including the intervention beneath the foundation. Theoretical models-expressions and experimental results from centrifuge tests have been used. The proposed numerical model is proven very efficient to describe the complex dynamic phenomenon and anticipate the seismic response after the employment of subsoil interventions.     

国外人文地理学关于记忆研究的进展与启示

记忆是当前西方人文社会科学的一个重要概念。记忆是与时间和空间密不可分的,空间是承载记忆的容器。二战以来,西方社会文化史家从时间的角度对记忆进行了大量研究。21世纪以来,关于记忆的研究也日益成为西方人文地理学者关注的领域。本文是对国外(主要是欧美)人文地理学者关于记忆研究的文献回顾,文章首先对记忆的相关概念进行阐释,然后从研究方法和研究主题的角度探讨了国外记忆地理的研究进展,探讨了国外人文地理学者关于记忆的研究内容以及对国内研究的借鉴与启示。总体来看,地理学的记忆研究还未形成固定的范式,研究的内容和方法体系都有待进一步完善。     

Wind(ow) of Change: A Systematic Review of Policy Entrepreneurship Characteristics and Strategies

What lessons can we learn from 40 years of policy entrepreneurship scholarship on policy entrepreneurs’ strategies and defining characteristics? While scholars have offered important insights, many questions remain open. This article systematically reviews 229 articles that were published between 1984 and 2017. Our findings provide (i) an analysis of policy entrepreneurship characteristics by sector, policy domain, individual/group, government layer, and geographical spread, (ii) an empirically based identification and classification of policy entrepreneurship strategies, and (iii) a statistical analysis of the relationship between policy entrepreneurs’ characteristics and strategies. We conclude with an agenda for future studies that will continue to examine new theoretical approaches that advance our understanding of the role that individuals and small groups play in the policy process.