Ion-cyclotron noise excitation in the topside ionosphere according to observations at the Intercosmos-14 satellite

A band-limited ELF emission having very distinct upper as well as lower cutoff frequencies, most probably determined by local parameters of the plasma, were discovered by the VLF experiment on board the Intercosmos-14 satellite (apogee height 1707 km, perigee 345 km; inclination 74°). This type of noise was observed in the day-time, at middle and low latitudes, at altitudes 600 km< h < 1400 km. The very clear case observed on March 5, 1976 is discussed in detail and arguments are listed that this ELF emission is locally generated ion-cyclotron noise. Calculations of the growth of the proton cyclotron resonance instability show that the growth may be positive if the loss cone angle of the energetic protons is sufficiently great. This condition is fulfilled at low altitudes near the mirror points. Depending on the width of the distribution function of energetic protons the growth of the Instability may be positive in the whole frequency band of the proton branch of ion-cyclotron waves or only in certain parts of that frequency band.     

Solar cycle variation of the total electron content around equatorial anomaly crest region in east asia

The monthly mean hourly values of total electron content data obtained at Lunping Observatory (geographic coordinates 25.00°N, 121.17°E; geomagnetic coordinates 14.3°N, 191.3°E) by using the ETS2 satellite beacon signal during the period from March 1977 to December 1990 have been used to analyze the solar cycle variations of total electron content (TEC) around equatorial anomaly crest region in East Asia. Positive, correlations were found between the 12 month running average of monthly mean TECs and sunspot numbers. By using the linear regression analysis method, the contour charts for real diurnal and seasonal variations of TEC at certain sunspot numbers were constructed and described. The diurnal variation of TEC was represented by the sum of its diurnal mean and first three harmonic components. The solar cycle variations of these components have also been discussed.     

An improved model of the variation of electron concentration with height in the ionosphere

An empirical model of the variation of electron concentration with height is described which overcomes some limitations found in practice with a previous widely used model (Bradley and Dudeney, 1973). In particular, the new model will generate more realistic variations of electron concentration with real height and virtual height, both including and excluding an F1-ledge. The model has no gradient discontinuities and will reproduce cases in which the F1-ledge does not have a true turning point. The model should prove very valuable for a wide range of propagation problems and for certain aeronomical applications.     

Fishing settlements in the Pskov region in the 16th century (according to archaeological data and written sources)

Numerous written sources report that an extensive system of special fishing villages called isads existed in the Pskov region in the 16th century. These villages were inhabited by professional fishermen and their fishing grounds were strictly delineated. Due to the analysis of scribes books, cartographic material analysis and exploratory excavations in the area, 314 sites were exposed. More than 60% of the fishing sites mentioned in the scribes books were mapped and the location of 20% more was determined by indirect information. Some of the isads which were located are partially studied by prompt or archaeological excavations. During the excavations of beach debris, some fishing gear dated to the late Medieval–Modern time periods were found. The combination of information obtained from the study of lake coastline changes, hydrological regime of waterways and water bodies of the Pskov region, and data on the economy and economics of the whole area under study give impetus to research into a number of problems related to natural environmental characteristics of the Pskov region for the period of study.     

Annual variations in the electron content and height of the F layer in the northern and southern hemispheres,related to neutral composition

Total electron content (TEC) data is presented for similar sites at ±35° latitude, and conjugate sites at ±20°, for several years near solar maximum. Comparison with the MSIS atmospheric model shows that the large seasonal anomaly at 35°N (an increase of 80% in TEC from October to April) is fully explained by changes in neutral composition. The small seasonal anomaly at 35°S also agrees with the MSIS model. Composition changes fail to account for the generally higher TEC in the northern hemisphere; this suggests the presence of an overall south-to-north atmospheric wind. Eastern declinations also contribute to enhanced TEC in the northern hemisphere, in the Pacific zone. The MSIS model predicts a semiannual variation of about ±25% in TEC at all sites, while observed changes are only about ±8%; thus we require some enhanced loss process near the equinoxes, particularly in September and October.Peak height calculations assuming a constant pressure level give a large semiannual variation in the F2 region: this is replaced by an annual variation when h_m F2 is calculated from diffusion theory. Heights calculated from the MSIS model are similar to observed values at ±35° latitude on summer days. A decrease of about 20km in observed heights on winter days is attributed to a poleward neutral wind; this wind also reduces the observed TEC. At night the height changes correspond to an equatorial wind, which is largest in summer and equinox. Observed day time TEC is greater at 20°N than at 20°S at all times of year, suggesting a northward transequatorial wind which is strongest near January and gives increased TEC and decreased peak height at 20°N.     

Semi-theoretical global models of the eddy diffusion coefficient based on satellite data

Long periodic density variations of the thermospheric constituents can be described by combined variations of two parameters: exospheric temperature and turbopause height. Two global models of thermospheric composition relying on exospheric temperature and turbopause height variations were presented by the authors in a previous paper. In this paper the turbopause height changes and their interpretation in terms of the eddy diffusion coefficient are discussed. The determination of the eddy diffusion coefficient is not unique as some assumptions have to be made with respect to the shape of the height profile of the eddy diffusion coefficient. Two models are presented: one for a height independent and one for a height dependent profile of the eddy diffusion coefficient. The models are discussed and compared with other results.     

Role of chemical effects in the formation of electron concentration depletions during HF heating of the ionosphere

A chemical mechanism which reduces the electron concentration in the upper ionosphere during HF heating is presented. It is based on the excitation of nitrogen vibrational levels by fast electrons which have appeared as a result of absorption of a radio wave. The vibrational excitation of nitrogen leads to an increase in ion-molecular exchange, followed by a depletion of the electron concentration because the positive molecular ions are very effective in electron -ion recombination. Two different models arc discussed. In the equilibrium model, the vibrational temperature has been established in the region disturbed by the radio wave. In the nonequilibrium model, the fast electrons are moving inside a thin duct where the time of vibrational-vibrational relaxation is greater than the time required by the excited molecules to leave the channel due to diffusion, so that the vibrational temperature cannot be established.     

On mechanisms for the formation of atmospheric irregularities in the solar terminator region

The mechanisms of formation of atmospheric irregularities (AI) by the solar terminator (ST) have been considered. All of these mechanisms are divided into two classes, linear or nonlinear, according to the mechanism of AI generation. All mechanisms determined by a moving step of some atmospheric parameter (pressure, temperature, and so on) belong to linear mechanisms for wave excitation. Mechanisms determined by instabilities in the atmosphere inside the ST region are nonlinear mechanisms. Examples are the gradient-radiatioe instability (GRI), which arises from the vertically inhomogeneous absorption of solar radiation, turbulence arising in the ST region, and the plasma instability in the evening hours caused by the increase of the electron pressure gradient inside the ST region.     

The mid-latitude trough in the electron concentration of the ionospheric F-layer: a review of observations and modelling

Experimental observations and theoretical modelling of the terrestrial mid-latitude trough are reviewed. The mid-latitude trough is considered as an F-layer phenomenon, and its relationships to the lightion trough in the topside ionosphere and to the plasmapause are discussed. The observed morphology of the mid-latitude trough is summarised. Recent evidence on plasma temperatures in the trough is examined. The physical processes that may be important in the trough region are listed. Large-scale computational models that include some of those processes are described and the results compared with observations. Deficiencies in the models and possible future developments are mentioned.     

The height of electron content changes in the ionosphere from ATS6 beacon data

A technique is described which uses relative changes in Faraday rotation and modulation phase of satellite radio signals to determine the median height of the enhancement (or depletion) in the electron density of the ionosphere. During the post sunrise formation of the F mlayer the incremental layers have a median height of around 210 km (±40) and in the afternoon the decremental median is above the peak at 340 km (±40) on a winter day. A winter night-time enhancement just after midnight appears as a thick layer extending upwards from the peak, with a median height at about 730 km. The method applies to large scale irregularities but not to small, dense, scintillation-causing irregularities for which Faraday and modulation phases do not represent the total electron content.     

纳税单位“真实”的一面——以徽州府土地数据考释为中心

本文拟以土地数据考释为中心，把有关徽州地区历史赋税资料与现代统计资料数据结合起来进行研究，从而就载籍时间断面数据的考查、纳税单位与耕地数据的区分、耕地面积“峰值期”的确定等几方面来探讨徽州特定时期的纳税单位能够反映“真实”的耕地面积，并以此为基点对嘉道时期的耕地面积进行再估计。     

Response of the equatorial thermosphere to magnetic activity analysed with accelerometer total density data. Asymmetrical structure

A great deal of accurate total density data from the CACTUS accelerometer experiment has been collected in equatorial regions during the last minimum of the solar cycle. Using these data, an analysis of the magnetically disturbed thermosphere has been performed with an improved resolution. Time delay of the response, latitudinal and longitudinal variations for solstice, day-time and night-time conditions have been studied. An attempt is made to interpret the behaviour of the thermosphere in the light of existing theories. An asymmetrical heating in latitude and a heating depending on longitude are needed in order to interpret the results.     

A quantitative assessment of intraspecific morphological variation in Gahagan bifaces from the southern Caddo area and central Texas

ABSTRACT

This investigation aggregates intact or reconstructed Gahagan bifaces from the southern Caddo area and central Texas to test the hypothesis that Gahagan biface morphology differs between the regions. The Gahagan bifaces (n=102) were scanned, then analyzed using a novel landmarking protocol and the tools of geometric morphometrics. Results provide a preview of the significant differences in Gahagan biface morphology expressed between the southern Caddo area and central Texas regions. The size discrepancy represents an inversion of current theoretical constructs that posit a decrease in tool size thought to articulate with an increase in distance from the raw material source. It is posited that the contrasting morphologies represent two discrete communities of practice; one (emergent Caddo horticulturalists) where Gahagan bifaces were enlisted primarily for burial and ritualistic activities, and the other (central Texas hunter-gatherers) where Gahagan bifaces were utilized over a longer time span in more practical and utilitarian contexts.     

"The moon" and "the blood": two emblematic symbols in headache and epilepsy according to scientific traditions of the Salerno Medical school and popular medicine in southern Italy

Before describing the state of knowledge on headache and epilepsy at the Salerno Medical School (SMS), we will briefly summarize in the first part its history through the centuries until the "golden period" of the 12th century when it reached its peak by outshining all others in teaching, studies and research. In the second part we will refer to Saint Donato, healer of epileptics in the south of Italy, whose worship is still alive today. The finding of common symbols in conceptions of headache and epilepsy, both in the scientific tradition of the School and in popular medicine, represents a link which is explicable by the wide dissemination of the school's doctrines.     

New discoveries in the Piramide Naranjada in Cahuachi (Peru) using satellite,Ground Probing Radar and magnetic investigations

The detection of buried earthen structures by using remote sensing techniques is still an open issue and a strategic challenge as crucial as it is complex. It is crucial because earthen archaeological remains are widely present thoughtout the world (in South America, Asia, Africa) and it is complex due to the subtle physical contrast between earthen remains and the surrounding subsoil.     

The use of wind direction data to predict pollution dispersal around the Port Kembla industrial area,New South Wales

Wind direction data were used to calculate the percentage time during which winds blew over the principal sources of air pollution at Port Kembla into each of the surrounding residential suburbs for each month of 1980. The percentage wind frequencies (PWFs) correlated well with measured concentrations of airborne metals in the suburbs and with measured rates of metal deposition in moss bags located in suburbs adjoining the air pollution sources. PWFs for all suburbs exhibited winter minima and spring-summer maxima, with the highest PWFs being calculated for suburbs south to south-west of the industrial area and the lowest for suburbs lying to the west. Where experimental data are not available, PWFs could provide an indication of air quality for land-use planning and zoning.     

何家村窖藏所见唐代金银器制作工艺述略

何家村窖藏出土金银器的制作工艺涉及金银器制作流程中的各个环节,能够系统反映唐代金银冶炼和金银器成形、修整、连接、装饰等全部工艺流程,包括冶炼环节的“灰吹法”工艺,成形环节的范铸、捶揲、锻打、闪打工艺,修整环节的切削、镟活、打磨工艺,连接环节的焊接、贴焊、卡合工艺,装饰环节的捶揲、錾刻、线刻、镂空、鎏金、花丝、编结、金珠焊缀、金筐宝钿、金镶玛瑙、金包玉工艺等,是唐代金银器制作工艺的全面体现。