Comparison of plasma densities in the daytime polar F-region measured by the AEROS-B and S3-1 satellites

A comparative study of ionospheric measurements obtained by different sensors on two satellites has shown excellent agreement between the principal techniques used to measure the plasma density and ion composition. Results from an ion mass spectrometer on the S3-1 satellite and from an impedance probe and a retarding potential analyzer on the AEROS-B satellite have been compared for five cases that represent the closest coincidence of measurements that occurred during the satellite lifetimes. The crossings occurred at high polar latitudes and the studies have indicated that invariant latitude is more important than altitude, geodetic latitude, or geomagnetic latitude in systematizing the data. The ratios of the mass spectrometer ion densities to the impedance probe electron densities resulted in an average value of 1.00 with a standard deviation of 6%. The composition percentage for the molecular and atomic ions from the retarding potential analyzer agreed generally within about 20% of the mass spectrometer measurements.     

High-latitude plasma densities and their relation to riometer absorption

A large number of D- and E-region electron density profiles from high latitudes have been analysed. These were derived from rocket-borne wave propagation experiments and—after careful screening—arranged according to riometer absorption. Statistical profiles for various degrees of absorption, including 0 dB, were established both for day and night. Furthermore, the height region predominantly contributing to the absorption has been identified. Finally a mean variation of the density of negative ions has been derived.     

Seasonal and tidal variations of neutral temperatures and densities in the high latitude lower thermosphere measured by EISCAT

Measurements of ion temperature, ion-neutral collision frequency and ion drift in the E-region from the period December 1984 to November 1985 are used to derive neutral temperatures, densities and meridional winds in the altitude intervals 92–120 km, 92–105 km and 92–120 km, respectively. Altitude profiles of temperature and density and their seasonal variations are compared with the CIRA 1972 and MSIS 1983 models and the effects of geomagnetic activity are demonstrated. Semi-diurnal tidal variations in all three parameters are derived and the comparison with lower latitude measurements is discussed.     

Comparisons of EISCAT and dynasonde ionospheric measurements: simple to moderately structured plasma densities

Plasma densities obtained from EISCAT's UHF incoherent scatter system are compared with profiles inverted from the digital ionograms of a co-located dynasonde. Excellent agreement is found for the bottomside ionosphere when conditions of horizontal stratification and classical photochemical equilibrium prevail. However, departures from such conditions are frequent and intense at Tromsø. Compensating errors of EISCAT calibration and long pulse convolution are resolved by analysis of power profile data. Good agreement is recovered for tilted and more complex ionospheric structure, provided that accurate echo location data are used to confirm a common volume. Monotonic inversion of the ionograms is inadequate. Dynasonde recordings are analysed to show characteristic structure in vertical and horizontal planes as a context for EISCAT measurements along a fixed (magnetic field) direction. Incoherent scatter and modern total reflection sounding, used together and coordinated in one consistent data reduction system, could produce a far more powerful ionospheric diagnostic program than either technique seems capable of providing alone.     

Winds,wind-shears and plasma densities during the initial phase of a magnetic storm from equatorial latitudes

Results of a sodium vapour release experiment carried out from SHAR (India), an equatorial rocket launching station, immediately after (⩽ 2 h) a storm sudden commencement (SSC) during the initial phase of a magnetic storm, followed by electron density measurements are presented. Many of the relevant atmospheric parameters, namely, neutral winds and their altitude variation, the magnitude of the shears in them, the neutral temperature with altitude by spectroscopic methods, diffusion measurements on the released trail, clues on the turbopause level and the electron densities including the structures (irregularities) in them were obtained. The results of the temperature measurements carried out independently on the sodium trail by means of a ground-based Fabry-Perot spectrometer, operating on the sodium D 1 line, resonantly scattered by the trail have already been reported by us (Ranjan Guptaet al., 1986). In this paper the effects of the excess temperature reported earlier and the rest of the measured parameters on the electron density profiles are evaluated using models and compared with the measurements.The formation of sharp layers of ionization have been explained on the basis of the electro-dynamical processes associated with the wind shears at a location, close to the edge of the equatorial electrojet belt. The significance of the changes in the neutral composition due to the enhanced neutral temperature and the low turbopause level, in increasing the base-level plasma densities by a factor of 3–5 are demonstrated and the possible role of plasma dynamics discussed.     

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.     

Model tuning and its impact on modelled climate change response: Hudson Bay sea ice, a case study

The impact of climate model parameterization is examined using Hudson Bay sea ice as a case study. The implicit diffusion of an upstream scheme used in a three dimensional ocean general circulation model is locally determined by using a one dimension proxy model of Hudson Bay with atmospheric, cryospheric and oceanic components. Using this proxy model, distinct pairs of values for the thermal conductivity of sea ice and thermal diffusivity of sea water are found that reproduce the current climatology of sea ice thickness in Hudson Bay. These pairs of values are subsequently used in a 3°C warming scenario. The resulting ice thicknesses are shown to be highly dependent on the choice of these pairs of values as well as the seasonal distribution of the warming.     

Solar activity effects on equatorial plasma bubble zonal velocity and its latitude gradient as measured by airglow scanning photometers

Using a new mode of scanning 630-nm photometer operation the zonal velocities of ionospheric plasma depletions were measured over Cachoeira Paulista in Brasil in two east-west planes tilted 30°N and 30° S with respect to zenith. The measurements cover a time period of approximately 2 years, from January 1988 to January 1990, a period marked by significant increase in solar activity of the ongoing cycle. The results have permitted a rather detailed evaluation of the local time and latitude variations in the zonal plasma bubble velocity as a function of solar activity. Although the mean trend in the velocity local time variation is a decrease from early evening to post-midnight hours, a strong tendency for velocity peaks is observed near 21 LT and midnight. The velocities as well as their height (latitude) gradients show perceivable increases with solar activity represented as sunspot numbers. The present results are compared with the ambient plasma velocities measured using the Jicamarca radar by Fejer el al. (1985), J. Geophys. Res. 90, 12249, with that measured on board the DE 2 satellite on the equatorial latitudes by Coley and Heelis (1989), J. geophys. Res. 94, 6751, and with various theoretical calculations, in an attempt to bring out the salient features of the plasma dynamics of the equatorial ionosphere.     

近代城市贫民阶层及其救济探析——以天津为例

With the development of industry and commerce after Tianjin’s opening as a treaty port, the urban poor were in an unfavorable situation in controlling the social resources. Facing a large number of urban poor, the state represented by government officials of various levels and the civil society represented by local gentry-merchants have clearly recognized the widened gap and increased opposition in all social strata and communities while the disintegration was close to cross the bottom line. It will affect the social harmony and cause unrests. Therefore, under their advocacy and support, all kinds of relief and charity institutes come into being and play a positive role in balancing the social wealth, helping the lower class, improving the social justice and maintaining the stability of social order. Translated by Luo Hui from Shilin 史林 (Historical Review), 2006, (2): 77–84     

东南亚华侨华人、港澳同胞与侨乡建设 --梅州市个案研究

本文论述和评价了东南亚华侨华人、港澳同胞在梅州投资办企业、捐资办学的实绩及其对梅州社会经济发展的作用、意义,从一个侧面展示了梅州侨乡社会经济发展的轨迹.     

Assessing the effects of geomorphological processes on archaeological densities: a GIS case study on Zakynthos Island,Greece

While geomorphological processes are considered key factors in the distribution of archaeological surface finds, few studies have attempted to quantify the relationship between artefact dispersal and erosional/depositional patterns. This paper compares Unit Stream Power Erosion Deposition model (USPED) and Revised Universal Soil Loss Equation (RUSLE) and integrates the results in the archaeological finds’ density map of Zakynthos Archaeological Project. The study area (Palaiokastro), with artefacts dated from middle Paleolithic to medieval times, includes a steep terrain with a surrounding plain area, where the downslope erosion has considerably modified the distribution of archaeological remains. Through this study, it is possible to identify relationships between high artefact densities and stable/non-eroded surfaces, and on the other hand, low densities and eroded surfaces. However, the results indicate a degree of spatial variability, which modifies the predicted relationship. The consideration of the effects of these temporal and spatial patterns is crucial for developing effective sampling methods and accurately interpreting the archaeological record.     

Calibration of electron densities for the EISCAT UHF radar

The accuracy of electron densities in routinely analysed EISCAT data is discussed and comparisons are made between the EISCAT measurements and those determined by rockets and an ionosonde.     

A comparison of ionization densities determined from spacecraft and incoherent scatter radar data

By comparing direct measurements taken from onboard Atmosphere Explorer spacecraft (AE), in eccentric orbit, with incoherent scatter radar (ISR) measurements taken from the ground, we illustrate both the merits and the difficulties involved in such comparisons. Five altitude profiles of ionization determined from AE, in near coincidence with ground stations making ISR measurements, compared favorably with the ISR data so long as the AE measurements were properly analyzed for the effects of variations in latitude and solar zenith angle along the spacecraft orbit.     

The ionospheric plasma flow and current patterns of travelling convection vortices: a case study

Following a short duration density enhancement in the solar wind, observed by the AMPTE/IRM spacecraft, transient disturbances appeared in the polar ionosphere in the prenoon local time sector which were identified as Travelling Convection Vortices (TCV). This event has been studied intensively by combining radar and magnetometer observations. EISCAT radar was operated in the special programme U.K.-POLAR which provides F-region plasma parameters from invariant latitudes around 72° at a rate of one sample per 15 s. The combined data set provides a detailed picture of the drift pattern of the plasma and the three-dimensional current distribution. There are two Hall current eddies drifting westward at a speed of 0.15° s⁻¹. The leading one circulating clockwise is associated with a downward field-aligned current and the oppositely circulating eddy with an upward current. The ionospheric conductivity seems to be enhanced in the leading vortex compared to the trailing, although the latter is connected to an upward field-aligned current. Still unexplained is the mechanism generating the electric field which drives the vortices. The direction of the electric field observed in the ionosphere is opposite to that expected if the source were a compression of the magnetosphere.     

Regionalization and the rescaling of agro-food governance: Case study evidence from two English regions

Some researchers detected a new-found subsidiarity in rural policy after England’s 2001 Foot and Mouth Disease epidemic, with regional and sub-regional institutions working together to implement an economic recovery strategy. While such research began to link debates on the new regionalism and the rescaling of agro-food governance, its conception of the latter focused too narrowly on the ‘turn to quality’, thereby overlooking other important aspects of food relocalisation. Based on interviews conducted in England’s South West and West Midlands regions, this paper examines whether the attitudes of key actors from regional and sub-regional governance institutions provided a sound basis for partnership working on the food relocalisation policies recommended in the Government’s Strategy for Sustainable Farming and Food. It finds different attitudes on the part of regional and sub-regional actors, with the former favouring regional foods and the latter local foods. Despite scepticism from both groups about the ability of the England Rural Development Programme (2000–2006) to promote food relocalisation, grants were awarded to both regional and local food entrepreneurs, suggesting that the programme contributed more to food relocalisation than previously thought.     

Experimental studies of daytime LF radio propagation and their implications for D-region electron densities

Measurements are presented of interference phenomena in amplitude and phase of VLF and LF signals along propagation paths from central England to the Norwegian Sea. The data are interpreted by means of the ‘wave-hop’ propagation theory, incorporating full wave evaluation of ionospheric reflection coefficients with realistic D-region models. No published electron density profiles are found which completely satisfy the experimental data, but modified profiles are presented which provide a better fit to the observations.     

Evaluation of electron and ion densities in the middle atmosphere from rocket-borne blunt probes

Detailed consideration has been given to the determination of electron number densities from conductivity data gathered by rocket-borne blunt probes in the middle atmosphere, and the intercomparison of these electron densities with those derived from other diagnostics. A definition of the difficulty of electron density determination from rocket-borne probes is presented. Also, the procedures for the determination of ion densities from blunt probe data in the middle atmosphere are critically evaluated. General aspects of particle collection by supersonic probes are compared with those of subsonic probes. It is noted that strong (× 10) compression regions will form in front of supersonic probes at altitudes up to 100 km, and the altered electron attachment rates could significantly affect indicated electron and negative ion concentrations. A summary of new analysis for determining electron densities from negative conductivities taken with a subsonic blunt probe is presented and the analysis is applied to data on several days where intercomparisons are possible. Blunt probe data from 31 January 1972 and 5 December 1972 (WI),² and 2 October 1975 and 29 September 1977 (WSMR)³ are reduced to predict electron density profiles. In the region of intercomparison, there is general agreement in the electron density predictions. The indications of electron density at altitudes below 70 km are new, and predict a region of moderately enhanced densities down to 45 km.     

A comparison of low- and mid-latitude D region electron densities derived from ground-based radio data

Electron density profiles, 70–110 km, for almost identical solar zenith angles over Central Europe and over Ahmedabad (India) are compared, avoiding seasonal ‘anomalies’. Low- and mid-latitude profiles agree very well in their structural features, the maximum deviation in magnitude being by a factor of 2 (around 90 km).     

Bone mineral densities in the prehistoric,Viking‐Age and medieval populations of Norway

Osteoporosis is a prevalent condition in Norway, as evidenced by the fact that this country has the highest reported incidences of hip and distal forearm fractures. Because recent studies suggest a higher bone density in rural populations compared with urban ones, increased physical activity is believed to be an important factor in reducing fracture incidence. In the present investigation, 185 femoral necks from the Schreiner Collection in Oslo were measured by means of a bone‐mass scanner. The bones, anthropological specimens ranging from the Stone Age to the Middle Ages, were separated into three groups: prehistoric (n = 36), Viking Age (n = 38) and medieval (n = 111). The medieval group was further separated into urban, rural and monastic populations. The examination showed that: (a) there was no significant difference at a 5% level in average bone mineral density (BMD) between the male and female material; (b) there was no significant difference in average BMD among the prehistoric, Viking Age, and medieval periods (P = 0.151); (c) there was no significant difference in average BMD between the rural and urban medieval material; (d) there was a significant difference in average BMD only between the monastic and the rural medieval material; (e) only the medieval material showed a significantly higher average BMD than that of today (P = 0.001). These findings may indicate that factors in addition to physical activity are important for normal BMD maintenance. Copyright © 2006 John Wiley & Sons, Ltd.