The phase relationships of the ionospheric signatures of Pc1 geomagnetic pulsations

In this study we consider the phase relationships between the oscillations of various ionospheric signatures associated with Pcl geomagnetic pulsations. Investigations using a simple analytical method and a numerical model, which has proved successful when applied to longer period pulsations, both suggest that Doppler velocity oscillations should be predominantly in anti-phase with oscillations of the rates of change of group range and echo amplitude. However, observations indicate that the Doppler velocity oscillations are in quadrature with the other two types of oscillations. Possible causes for this discrepancy are suggested.     

A study of wave packets and phase jumps in low latitude Pc3 geomagnetic pulsation

An array of four low latitude induction coil magnetometer stations has been used to study the spatial and temporal characteristics of Pc3 pulsations over a longitudinal range of 17° at L = 1.8 to 2.7 in southeast Australia. A preliminary study of individual Pc3 wave packet structure at the azimuthal stations has established the existence of phase jumps between wave packets at low latitudes, similar to those observed at synchronous orbit and at higher latitude ground stations. However, there did not appear to be any obvious pattern in phase jump occurrences between stations or signal components.     

Temporal and spatial distribution of the spectral components of foF2

A spectral analysis of almost all available monthly median of the maximum plasmafrequency in the F-region (foF2) was performed. Some evidence for a significant tidal influence on the diurnal and semidiurnal variation has been found. The declination effect (Eyfrig, 1963) appears in our spectral presentation as a dependence of the degree of the seasonal variation and of the phase of the 24 hour period on the magnetic declination. The most peculiar phenomenon is the different variation of the annual component in North America and Eurasia with the sunspot number. There are several indications that the variation of (foF2) is also influenced by the variation of the gravitational potential. Some other results are presented which are believed to be related to dynamic processes in the F-region.     

The spatial extent of agglomeration economies across the wage earnings distribution

We investigate the spatial extent of agglomeration economies across the wage earnings distribution using economic mass (total employment) in four distance bands around each individual’s establishment in a quantile regression framework. We control for observable and unobservable individual and establishment characteristics. Remaining endogeneity in the model is assessed with a set of instrumental variables. Results indicate a positive effect of economic mass on wage earnings up to 25 km away from the establishment. The spatial extent of agglomeration economies is similar across the wage earnings distribution. However, increases in economic mass shift the wage earnings distribution in a nonsymmetric way.     

A study of pearl pulsations in the equatorial region of India

Pearl pulsations in the equatorial region, despite their relative paucity, are known to exhibit definite features in their diurnal, seasonal and annual occurrence patterns. In the present study, attempts are made to examine and bring out in detail some more aspects of these pulsations recorded at Choutuppal (Geomagnetic latitude: 7°28′N) over a period of nine years during 1967–1975. The mid-period (t) of pearls is found to bear a linear relation to the pearl repetition period (T) and is of the form T = 70t + 11.2. The periods of pearls are seen to be influenced by the average magnetic activity level prevailing during the preceding few days rather than that existing on the day of pearl occurrence. There is an increase in the mid-frequency of pearls that occurred succeeding a magnetic disturbance particularly when the disturbance persisted over some days. The amplitude ratio (H_x/H_y) averaged for each two-hourly interval is seen to attain a value of unity around local midnight and decrease towards the dawn and morning hours. From these results, namely the dependence of mid-frequency of pearls on the average magnetic activity (represented by (Σ Kp >) during the preceding few days and the occurrence of shorter period pearls even after a few days following a magnetic storm, it is suggested that the plasmapause takes much longer time to re-establish to the quiet time position. In the alternative, it may be visualized that possible presence of localized regions of high plasma density gradients inside the plasmasphere after the cessation of a storm might provide favourable conditions for the generation of shorter period pearls.     

A study of the thermospheric forces at a high latitude site on two days of differing geomagnetic activity

Data from the Fabry-Perot Interferometer and Dynasonde at Halley (75.5°S, 26.6°W, L ∼ 4.2), Antarctica, have been used to calculate the forces acting on the high latitude thermosphere. Two case studies of the forces have been undertaken to study why the thermospheric zonal wind speeds are typically so different on nights with different geomagnetic activity. One case study analyses the forces on a geomagnetically active night and the other analyses them on a geomagnetically quiet night. Even on the geomagnetically active night, it is found that the ion drag force is not necessarily the largest force at any one time. Simple comparison of the magnitudes of the forces does not make it very clear which ones dominate in controlling the motion of the thermosphere. This can be seen more clearly by rewriting the momentum equation so that the neutral velocity is expressed in terms of the ion velocity, and the other forces normalized by the ion density. It then becomes clear that, in the evening, the differences in the neutral velocity are due to increases in both ion density and ion velocity, while in the morning, only changes in ion density are important. Thus, although the ion drag force is often not the largest force, it appears that changes in it can account for the variations in neutral velocity between the two nights that were studied.It has also been shown as part of the analysis that whether or not the viscosity needs to be considered when calculating the ion drag force at an altitude of 240 km depends on the ion density profile. If the profile has a single peak then it is only necessary to consider the ion density at 240 km. It is, however, possible that just considering the ion density at this altitude may lead to an underestimate of the effective ion drag force if more than one peak is present.     

Integration and ethnic spatial concentration: the changing distribution of the Anglo-Jewish community

"This paper identifies the changing locational patterns of the Jewish community in Britain during the past century. Two major trends are identified. At the national level there has been movement out of many small provincial communities to the large urban centres, particularly Greater London and Manchester. Within the city, there has been movement out of the traditional inner city ghettos to the suburbs, thus reflecting the upward socio-economic mobility and integration of what was an immigrant group. Both these trends closely mirror the general patterns of population movement in Britain during the twentieth century." The lack of reliable data for the Jewish population is noted, and a methodology is suggested for identifying the changing locational patterns and intensity of Jewish community life. The method is applied to the case of Greater London.     

Numerical modelling of 3D fluid flow and oxygen isotope exchange in fractured media: spatial distribution of isotope patterns

An understanding of fluid flow, mass transport and isotopic exchange in fractured rock is required to understand the origin of several geological processes including hydrothermal mineral deposits. The numerical model HydroGeoSphere simulates 3D advection, molecular diffusion, mechanical dispersion and isotopic exchange in a discretely fractured porous media, and can be used to better understand the processes of mass transport and isotopic exchange in fractured rocks. Study of ¹⁸O isopleth patterns for different types of fractures and fracture networks with a range of structural complexity and hydraulic properties shows that fracture properties and geometry control mass transport and isotopic exchange. The hydraulic properties, as well as the density, spacing, and connectivity of fractures determine the isotopic patterns. Asymmetries in the geometry of oxygen isotope patterns could be used to determine the direction of hydrothermal fluid flow.     

Detecting hidden violence: The spatial distribution of excess mortality in Rwanda

Existing sub-national studies on the geography of armed conflict mainly focus on observed battle events. Other dimensions of the conflict cycle, including battle events that remain undetected in news reports, one-sided violence against civilians and the indirect death toll, have gone largely unstudied due to lack of systematic data. This article demonstrates how these different dimensions of a conflict cycle can be detected and how their relative importance can be assessed. The basic tools include population census data, principal component analysis and spatial analysis. When applied to the Rwandan case, the method reveals high excess mortality from the civil war, genocide, (counter)insurgency and the refugee crisis. Hidden violence is detected by presenting the first quantitative evidence to date of high excess mortality in Gisenyi, the northwestern province which was the location of (counter)insurgency and served as a corridor for more than a million refugees. The spatial regression analysis indicates that both the refugee crisis and (counter)insurgency contributed to a high death toll in Gisenyi. This latter finding is important because it provides empirical weight in support of contentious qualitative reports by various human rights groups.     

The spatial distribution of population in Spain: An anomaly in European perspective

We exploit the GEOSTAT 2011 population grid with a very high 1 km² resolution to document that Spain presents the lowest density of settlements among European countries. Only a small fraction of the Spanish territory is inhabited, particularly in its southern half, which goes hand in hand with a high degree of population concentration. We uncover through standard regression analysis and spatial regression discontinuity that this anomaly cannot be accounted for by adverse geographic and climatic conditions. The second part of the paper takes a historical perspective on Spain's settlement patterns by showing that the spatial distribution of the population has been very persistent in the last two centuries, and that the abnormally low density of settlements with respect to European neighbors was already visible in the 19th century, which indicates that this phenomenon has not emerged recently as a consequence of the transformations associated with industrialization and tertiarization. Using data on ancient sites, we find that Spain did not feature scarcity of settlements in comparison to other countries in premedieval times, suggesting that its current anomalous settlement pattern has not always existed and is, therefore, not intrinsic to its geography.     

Role of the plasmapause and ionosphere in the generation and propagation of pearl pulsations

The source of Pc 1 (pearl) pulsations observed in the course of the local morning hours on 7 December 1977 has been determined by the amplitude and group delay methods. The frequency of pulsations exhibit the typical diurnal variation with the maximum frequency during dawn hours. The source location of pearls during every 1-h interval is compared with the position of the plasmapause inferred from the GEOS I measurements and from previous statistical analysis. It is shown that the source of high-frequency pulsations (f > 1 Hz) is well inside the plasmapause whereas low-frequency pulsations (f < 1 Hz) occur near the plasmapause. The source of pulsations is displaced to higher L-values in the course of the local morning hours and this displacement is associated with the decrease of the frequency of pulsations. The source displacement is much more pronounced than the simultaneous movement of the plasmapause position. These observations imply that the model of the Pc1 generation which locates the source only at the plasmapause has serious shortcomings. A model is discussed which takes into account the generation of Pc1 pulsations also well inside the plasmapause and the properties of the waveguide propagation of waves in the ionspheric duct.     

Analysis of the connections between solar wind parameters and day-side geomagnetic pulsations based on data from the observatories Nagycenk (Hungary) and Uzur (U.S.S.R.)

A comparison is made of results obtained at two widely separated observatories, Nagycenk in Hungary and Uzur in Soviet Siberia (both at geomagnetic latitude 48°) and the connection is studied between pulsation parameters and parameters of the interplanetary medium. It is concluded that, in spite of differences in recording and processing, the results are similar and confirm earlier suppositions about these connections. Hypotheses about the location of the excitation clearly favour the pre-shock interplanetary medium with reflected protons counterstreaming to the solar wind. Propagation through the shock wave and the magnetopause, as well as infra-magnetospheric propagation, may later alter certain parameters of the pulsations.     

Analysis of the spatial distribution of geochemical signatures for the identification of prehistoric settlement patterns in ADE and TMA sites in the lower Amazon Basin

The Archeological Dark Earth (ADE) and Terra Mulata (TMA) anthrosols found at Juruti, on the lower Amazon River, extend over a wide area located within the local ferralsol domain. The ADE soils are dark in color and contain large quantities of fragmented ceramics, while the TMA soils are also relatively dark, but lack ceramics. Multi-element chemical analyses of soil samples of ADE and TMA from the A2 horizon (depths of 10–20 cm) indicated that the ADE soils are characterized by higher concentrations of P₂O₅, CaO, K₂O, MgO, Cu, Mn, and Zn, while the TMAs have median levels of these compounds, and the ferralsols have much lower concentrations. These chemical elements make up the geochemical signature of these anthrosols, whereas Al₂O₃, Fe₂O₃, TiO₂, Cr, Sr, La, Li, Ni, Pb, V, Y, and Zr characterize the geochemical signature of the ferralsols, which was identified partially in the ADEs and TMAs. The isoline maps of these two geochemical associations permitted the delimitation of the different areas and the identification of the ADEs as sites of long-term human occupancy, and the TMA as an area of temporary occupation associated with agricultural activities. Seven villages were delimited within the study area, and were separated by corridors of ferralsols. These settlements were established on the riverbank, with the more temporary cultivated areas behind them, running almost parallel to the river. The identification of functional patterns based on geochemical associations, the abundance of ceramic material, and concentrations of organic matter, indicated that an area of more than 350 ha was occupied.     

The components of the annual line in geomagnetic field elements

The annual cycle of the strength of the geomagnetic horizontal field shows a local time dependence. Recent explanations for this invoke a ring current or magnetospheric source for the night-time, and an ionospheric source for the daytime annual waves, but the relative importance of each source has been uncertain. Harmonic dials of the annual waves in H from harmonic analysis at several local times and observatories are presented. Comparison with corresponding analyses of observed ionospheric winds supports the two source model. It is shown that both the magnetospheric and ionospheric components in H are 180° out of phase across the equator. But because of differing amplitudes of the two components across the equator, the net annual waves are about 160° out of phase across the equator.     

The vernal-autumnal asymmetry in the seasonal variation of geomagnetic activity

In intervals in which the polarity of the main solar dipole field is stabilized, a 12 month wave occurs in geomagnetic activity (indices aa, Ap, Dst) with its maximum in one of the equinoctial periods. Whether the vernal or the autumnal maximum is greater depends on the polarity of the main solar dipole; the existence of the wave may be explained by the north-south asymmetry in the main solar dipole field. The results favour the southward component of the interplanetary magnetic field as the decisive factor for geomagnetic activity.     

The effect of the spatial distribution of state-owned enterprises on the location of private-owned enterprise births

The impact of the incumbent state-owned enterprises (SOEs) on the births of new private-owned enterprises (POEs) in China is a central concern for the government and society. In this paper, we apply agglomeration theories to distinguish the linkages between SOEs and POEs. Using China's 2008 economic census, the 2007 Input-Output Table, and the 2005 population census, we measure the formation of new POEs at the city-industry level, and the agglomeration forces of distance proximity to inputs, outputs, labor, and technology. More explicitly, we measure the extent to which local SOEs provide relevant inputs, consume outputs, employ similar workers, and use similar technology. Our findings indicate that overall, incumbent SOEs hinder the formation of new POEs. For manufacturing, the entry of new POEs is significantly lower in places where more upstream SOEs are concentrated. For services, the entry of new POEs is significantly lower in places where more upstream and downstream SOEs are concentrated. However, the agglomeration effects from the incumbent POEs are either insignificant or significantly positive.     

Effects of commune-internal migration in Finland on the spatial distribution of population and on dwelling house utilization

"The article is based on a programme of research which has been pursued for some years with the purpose of describing the extent and spatial orientation of commune-internal migration [in Finland], a topic about which very little has previously been known, relating this form of migration to total population movement and to dwelling house requirements and utilization. The analysis yields information on the dynamics of population changes occurring in areas on the margins of permanent settlement, while at the same time taking into consideration the effects of regional and in particular housing policy decisions upon the spatial distribution of population."     

Morphology of low-frequency waves in the solar wind and their relation to ground pulsations

Three classes of low frequency waves (period range 20–80 s) were identified using data from the UCLA fluxgate magnetometer experiment on board the ISEE 2 spacecraft. These are continuous pulsations similar in type to Pc 3, band-limited oscillations distinguished by mixed period fluctuations, and relatively isolated wave bundles. The waves were preferentially observed when the interplanetary magnetic field (IMF) direction was sunward and were most common when the cone angle, i.e. the angle between IMF and the Sun-Earth line (θ_xb) was often between 15° and 45°. Their frequency is proportional to the IMF magnitude.Comparison between the waves observed on board the ISEE 2 spacecraft and the Pc 3–4 recorded simultaneously at a mid-latitude ground station, Oulu (L = 4.5), showed that similarity of spectra of the waves in the spacecraft and on the ground was very rare and that correspondence between the events in space and on the ground was extremely low.     

两种不同环境控制下砂岩类文物岩石材料剥落特征及形成机制差异性的研究

为了研究不同环境对砂岩类文物岩石材料劣化的影响和控制,本工作以北京西黄寺和柬埔寨吴哥遗址周萨神庙两种砂岩类文物岩石材料为研究对象,从砂岩表层剥落形态、物理性质、化学矿物成分及微观结构变异四个方面对剥落特征进行了系统论述,并从岩石特性和环境因素两方面对剥落形成机制进行了分析.研究结论认为周萨神庙砂岩表层剥落比西黄寺砂岩更严重,这是由于其材料本身特性略差、大气降雨作用和生物活动更频繁造成的.本工作的测试方法及剥落形成的机制可为类似研究提供参考.