Night-time electron density of the lower ionosphere in the South Atlantic Geomagnetic Anomaly region obtained with a LF/VLF oblique ionosonde

Studies of the reflectivity of the night-time lower ionosphere in the region of the South Atlantic Geomagnetic Anomaly have been carried out for the period August 1980 to July 1981, using data collected by an oblique ionosonde at low/very low frequency, in the southern part of Brazil, near the centre of the Anomaly. From these studies monthly average behaviour of heights and reflection coefficients of the lower ionosphere between 15 and 60 kHz have been deduced. Assuming an exponential model of the electron density distribution in the lower ionosphere the appropriate numerical parameters were calculated using a trial-and-error approach with ‘full wave’ calculations and iterative computational techniques. For the period considered three sets of parameters could satisfactorily represent the lower ionosphere in the anomalous region and in the period analysed: one valid from August to November 1980, one valid from December 1980 to March 1981 and the other valid from May to July 1981. April 1981 seemed to present anomalous behaviour.     

EISCAT observations of a sequential Es layer

An experiment was carried out during the summer of 1982, using the EISCAT incoherent scatter radar, to investigate sequential Es: layers of enhanced electron density in the ionospheric E-region. Results are presented for an event occurring on 30 July, and the observations compared in a simple way with those expected from the wind-shear theory. Comparisons are made with data available from ionograms from Tromsø, Kiruna and Sodankylä, at which sites Es layers are also seen, though with differences that may be due to differences of wind direction.     

F-region neutral winds from ionosonde measurements of hmF2 at low latitude magnetic conjugate regions

The behavior of the F2-peak height difference Δh_mF2, between low latitude magnetic conjugate points, is known to be governed by thermospheric winds blowing along the magnetic meridian. Ground based ionosonde measurements of h_mF2, at two pairs of magnetic conjugate stations, have been analysed in conjunction with the results of a realistic dynamic computer model of the tropical ionospheric F-region, to determine thermospheric wind velocities. The behavior of monthly average values of the sum, at conjugate points, of the thermospheric horizontal wind velocity component in the magnetic meridian, at low latitudes, has been inferred for months of solstice and equinox, as well as for periods of low and high solar activity.     

Some features of h-type Es at Uppsala

The partial reflection technique was used to study h-type Es over Uppsala for three months in 1973. This showed that the phenomenon was most common just after 0600 and before 1800. A statistical study of the occurrence of Es over Uppsala for the solar minimum and solar maximum years 1963 and 1968 confirms this result and shows that this type of Es occurs about twice as often in solar minimum years than in solar maximum years. There is a strong maximum in summer months. The downward movements of Es-h decreases as the height decreases, consistent with the hypothesis that this type of Es is generated by internal gravity waves.     

Insect and clitellate annelid traces in mesofossil assemblages from the Cretaceous of Australasia

Mesofossil assemblages from several Cretaceous and Cenozoic units across Australia and New Zealand provide new evidence of insect and annelid behaviour. The earliest scale insects (Diaspididae, Coccoidea) from Australasia are described and represented by three scale morphotypes. The mesofossil assemblages also reveal clitellate annelid cocoon morphotypes, three morphotypes of arthropod coprolites and several insect piercement structures on gymnosperm leaf or stem fragments, possibly related to feeding or more likely oviposition. This research offers a new avenue for detecting cryptic terrestrial invertebrate groups and their interactions, particularly with plants, in the fossil record. The fossils demonstrate that insect/invertebrate activity can be preserved and identified in mesofossil suites, that such traces and exoskeleton fragments are relatively common in acid-extracted mesofossil suites, and that recognizable categories occur on multiple landmasses and at various ages.     

Estimation of the true ionospheric height profile,with a continuous gradient,from oblique sounding data

A technique to calculate the true height ionospheric profile from multifrequency oblique soundings is proposed. In the classic isotropic statement of the problem, it avoids a discontinuity in the gradient of electron density with height at nodal points and. as shown in test examples, it considerably increases the accuracy of the reconstructed profile as compared with well known, currently employed methods. The influence of the geomagnetic field is taken into account in the technique by constructing the equivalent isotropic ionogram. Both numerical and experimental results are presented and discussed.     

Electron density profiles over the Southern Ocean from oblique incidence ionograms

This paper presents a first attempt to use oblique incidence ionograms over the 4500 km path from Sanae, Antarctica, to Grahamstown, South Africa, to deduce information about the ionosphere in the intervening regions. It is shown that existing methods for the reduction of oblique incidence ionograms to N(h) profiles give reasonable results even over the two-hop path involved. By comparison with vertical incidence ionograms made from a research ship below the reflection regions it is shown that the maximum observed frequency is normally limited by conditions at the southernmost reflection point, though this may be modified by ionospheric tilts, sunrise and sunset.     

Three solar cycles of day-time southern hemisphere Es activity

The hourly values of the ionosonde parameters f_oE_s and f_bE_s for times near mid-day have been examined over three solar cycles 1947–82. The daily parameters were studied for two southern hemisphere stations: Christchurch (temperate zone) (−43°.6′ geographic, −48°.1′ geomagnetic) and Rarotonga (subtropical) (−21°.2′ geographic, −20°.7′ geomagnetic). The data represent the longest such analyzed sporadi-E record in the literature. The seasonal variations of per cent occurrence of f₀E_s ⩾ 5 MHz and f_bE_s ⩾ 4 MHz for both stations show no sunspot dependence, strong activity in local summer and, in the case of Christchurch, minor enhancements in local winter. Long-term f_bE_s occurrence is closely associated with Zurich sunspot number R_z (correlation coefficients 0.93 for Christchurch and 0.76 for Rarotonga) with all seasons, showing the same in-phase R_z control for both stations. Long-term f_oE_s occurrence for both stations and for all seasons exhibits no dependence on R_z. There is evidence of a 6 year period in seasonal f_oE_s activity for Rarotonga. The data show a large and unexplained systematic decrease in f_oE_s occurrence for both stations and for all seasons by a factor of about 3 from 1947 to 1982.     

Structure in the seasonal variations of Es at southern latitudes

The diurnal variations of the seasonal characteristics of sporadic-E occurrence have been studied by analyzing a large data set of ionosonde parameters for two southern hemisphere stations. The seasonal patterns are found to display anomalous short-term variations apparently not associated with solar control or the effects of dynamic meteorology.     

Synthesis of oblique ionograms from vertical ionograms using quasi-parabolic segment models of the ionosphere

This paper describes a method of synthesizing oblique ionograms from vertical ionograms based on representing the ionosphere by multiple quasi-parabolic segments (QPS). The advantage of this approach is that it allows analytical solutions to be obtained for several ray parameters when the Earth's magnetic field is neglected and the ionosphere is spherically stratified. The no-field results are representative of the ordinary mode. In addition, results for the extraordinary mode can be obtained by introducing a perturbation to the effective frequency and modifying the no-field results. The method is illustrated by comparing synthesized oblique ionograms with observed ionograms and with results obtained for the ordinary mode using the classical method.     

Roman traces in Germania magna: New thermoluminescence and pIRIR290 data from a lime kiln at Bergisch Gladbach,Germany

The applicability of a post‐infrared infrared stimulated luminescence (pIRIR₂₉₀) protocol and two different thermoluminescence (TL) protocols—a single aliquot regeneration (SAR) and a multiple aliquot additive dose (MAAD)—was tested on six polymineral fine‐grain (4–11 μm) samples extracted from the wall remains of a Roman lime kiln and a Roman roof tile. These remains had been excavated close to Bergisch Gladbach, which was at that time part of Germania magna. For the pIRIR₂₉₀ measurements, no dependence of D_e on first‐stimulation temperature was detectable, and the standard first stimulation temperature at 50°C was adopted. Fading tests and dose‐recovery tests were made for all samples. Background subtracted glow curves were recorded up to 480°C for TL after a preheat of 220°C for 120 s. A‐values were determined for all TL and pIRIR measurements. The results for all three protocols were fairly consistent, and TL and pIRIR₂₉₀ protocols are shown to be suitable to estimate reliable equivalent doses for the fired kiln walls. The resulting ages are in agreement with the expected time range—Roman Iron Age—and with independent age control provided by radiocarbon ages of animal bones and charcoal from the firing chamber.     

New insights into the neolithisation process in southwest Europe according to spatial density analysis from calibrated radiocarbon dates

The agricultural way of life spreads throughout Europe via two main routes: the Danube corridor and the Mediterranean basin. Current archaeological literature describes the arrival to the Western Mediterranean as a rapid process which involves both demic and cultural models, and in this regard, the dispersal movement has been investigated using mathematical models, where the key factors are time and space. In this work, we have created a compilation of all available radiocarbon dates for the whole of Iberia, in order to draw a chronological series of maps to illustrate temporal and spatial patterns in the neolithisation process. The maps were prepared by calculating the calibrated 14C date probability density curves, as a proxy to show the spatial dynamics of the last hunter-gatherers and first farmers. Several scholars have pointed out problems linked with the variability of samples, such as the overrepresentation of some sites, the degree of regional research, the nature of the dated samples and above all the archaeological context, but we are confident that the selected dates, after applying some filters and statistical protocols, constitute a good way to approach settlement spatial patterns in Iberia at the time of the neolithisation process.     

Using the combined resources of amateur radio observations and ionosonde data in the study of temperate zone sporadic-E

This paper discusses how key characteristics of temperate zone sporadic-E can be determined by making use of the combined experiences of amateur radio observations and ionosonde data. There are advantages to using this unified approach in the study of the phenomenon, and to understand and draw conclusions from the data. A brief history of amateur radio involvement in the phenomenon is provided along with actual radio observations in the 50 MHz band. Long term ionosonde data collected at Boulder, Colorado were examined using the benefit of radio experience in order to find what correlations may exist with other phenomena. Some significant conclusions regarding characteristics of temperate zone sporadic-E can be drawn through this approach.     

Structure in the seasonal variations of ionospheric Es occurrence in the South Pacific

A survey is presented of the occurrence of strong ionospheric sporadic-E for South Pacific ionosonde stations covering a period of many years. The seasonal characteristics indicate the presence of strong non-solar effects with, for example, subtropical data showing strong afternoon enhancements of E_s activity in the autumn.     

The technology of Copper Age funerary pottery from Central Italy: An integrated study of compositional analyses and manufacturing traces

The paper focuses on ceramic vessels unearthed from Copper Age necropolises located in the area of the modern city of Rome and commonly attributed to the Rinaldone culture. The peculiar vessels' shapes, mainly associated with the consumption of beverages, their accuracy of manufacture and the very low impact of these ceramic morphologies in the coeval household assemblages lead to the study of such an apparently selected production through a multidisciplinary research. Petrographic analysis, X-ray fluorescence (XRF) and X-ray diffraction (XRD) integrated with the analysis of manufacturing traces and X-ray investigation suggest the transmission of technological choices, which remained unchanged over almost two millennia.