Seasonal and latitudinal variations of the lower thermospheric tidal winds from meteor radar measurements in the U.S.S.R.

Meteor wind results obtained at 93–95 km altitude at seven sites, six in the Soviet Union and one in Antarctica, between 1965 and 1985 are reported. Attention is focussed on the amplitudes and phases of the semi-diurnal tide, showing a 22-yr oscillation, and of the generally weaker diurnal tide. The measurement results are compared with the results of theoretical models.     

On the relation between diffusion coefficients and height from radar meteor echoes

Diffusion coefficients derived from radar meteor echoes and corrected for atmospheric wind shears have been used to investigate a linear relation between diffusion and height in the atmosphere. The results of a least square fit and of a method in which both variables are considered subject to errors are presented and discussed. The present results seem to indicate that the relation between diffusion coefficient and height is not as simple as supposed. Scale height values derived from these data are not consistent with accepted values in the atmosphere.     

Response of high frequency radar to meteor backscatter

The response of a High Frequency (HF) Radar System to echoes backscattered from underdense meteor trails is calculated. Three propagation modes are identified according to whether the echo is received along the direct (line-of-slight) path, or along two possible paths from beyond the horizon involving ionospheric reflection. The system response contours in terms of meteor radiant position on the sky are presented in the altitude-azimuth and celestial ecliptic coordinate systems. Diurnal echo rate curves are deduced for point radiants, which correspond to meteor showers and for a density distribution of radiants which is appropriate to sporadic meteors.The calculations are compared with observations of integrated meteor echo power from sporadic meteors made with an experimental radar system at frequencies throughout the HF band. Satisfactory agreement is reached between predictions and observations as functions of time of day, radar frequency and range. The extension of observations to include ionospherically propagated echoes permits meteor echo rates to be simultaneously monitored over an area of the Earth's surface of the order of 10⁶ km² with a single radar system.A greater than normally accepted echo rate is required to explain our observations. However, we believe that this enhanced rate is consistent with the true echo height distribution and the attenuating effects of trail initial radius and diffusion, which are particularly severe at the radar frequencies normally used for meteor detection near and beyond the top of the HF band. Our echo rate is consistent with the meteoroid cumulative mass distribution which may be inferred from a simple interpolation between satellite and visual measurements.     

The British Isles and Great Moravia in the early middle ages

The work of the Irish or Iro-Scottish missioneries on the continent of Europe in the sixth to eighth centuries is well known. An attempt is made here to show how the characteristic design of early Celtic churches found its way partly via Bavaria, where for example the Irishman Virgil became bishop of Salzburg in the mid-eight century, into Moravia, along with other Iro-Scottish cultural influences, a century or so before the well-known Christianizing mission launched into that area from Byzantium by the two brothers SS Cyril and Methodius, in 863.     

The British Isles and Great Moravia in the early middle ages

The work of the Irish or Iro-Scottish missioneries on the continent of Europe in the sixth to eighth centuries is well known. An attempt is made here to show how the characteristic design of early Celtic churches found its way partly via Bavaria, where for example the Irishman Virgil became bishop of Salzburg in the mid-eight century, into Moravia, along with other Iro-Scottish cultural influences, a century or so before the well-known Christianizing mission launched into that area from Byzantium by the two brothers SS Cyril and Methodius, in 863.     

Specimens of Modern Mascots and Ancient Amulets of the British Isles

Folklore in the English and Scottish Ballads. By Lowry Charles Wimberly. Illinois: Univ. of Chicago Press (Cambridge Univ. Press), 1928. 9" x 5 7/8". Pp. xiii + 466. 25s.     

Reconceptualizing Resistance in the Historical Archaeology of the British Isles: An Editorial

The present resonates with the harmonics of past events. Our archaeologies, because they deal with the everyday materiality of life, should not neglect to concern themselves with the domination of past people, since many similar forms of oppression persist. Moreover, we should consider the resistance to such domination. Rather than seeing resistance as simply reactive a problem which has generated much criticism—we can reconceptualize it to encompass a more nuanced understanding of the volition and agency of people in inferior positions of power. This lends new strength to the role of archaeologists in representing historical narratives of resistance.     

One full-day radar measurement of lower stratospheric winds over Jicamarca

The lower stratospheric wind field is measured simultaneously at several altitudes for 24 h on 23–24 May 1974 using the Jicamarca radar in Peru. Maximum entropy spectral analysis is used to estimate echo power spectra from the measured autocorrelation functions which are truncated beyond the maximum time lag of 6.65 s. The fluctuating wind velocity is resolved into steady and tidal components. A vertical shear of 2–3 m s⁻¹ km⁻¹ is observed throughout the time of observation in the zonal wind. The mean zonal wind is in good agreement with the Lima-Callao radiosonde data obtained in the same month. A very large diurnal component, of amplitude 1–5 m s⁻¹ is observed in the zonal wind in the lower stratosphere. However it appears that a semidiurnal oscillation below the tropopause is predominant.     

Seasonal variation in mesospheric semi-diurnal tides. Comparison of meteor radar observations and results from an excitation source model

The seasonal variation of the semi-diurnal tide is well established in the upper mesosphere from meteor radar observations, such as those made at Garchy (France). A classical propagation model, using a realistic excitation source from ozone and water vapour solar heating, can account for most of the seasonal variation characteristics, and in particular the strong difference between summer and winter features.     

The Mineralogy of Bronze Age Copper Ores from the British Isles: Implications for the Composition of Early Metalwork

Numerous analytical studies during the latter half of this century have contributed to the compilation of a large compositional database of Early to Middle Bronze Age copper-based artefacts revealing distinctive impurity patterns which appear to change over time. However, attempts to relate these data to copper ore sources proved problematic in the absence of firm evidence for the location of prehistoric copper mines. Over the last fifteen years this situation has changed dramatically with the discovery of numerous Early and Middle Bronze Age copper mines in England and Wales. This study is the first attempt at a comprehensive mineralogical survey of the principal mines investigated to date in order to define the likely composition of the copper ores as mined in antiquity for comparison with the artefact database. The study suggests that the majority of these mines can only have produced essentially pure copper. Only one mine, Ross Island, is likely to have produced copper with a significant level of impurities. The relative purity of the known ore sources is contrasted with significant levels of various metallic impurities among the analysed artefacts, leading to the conclusion that metal circulation and mixing may have been more extensive than previously thought even during the earliest part of the Bronze Age.     

Long period wind oscillations observed by the Kyoto meteor radar and comparison of the quasi-2-day wave with Adelaide HF radar observations

We have detected wind oscillations with periods ranging from 1.4 to 20 days at 80–110 km altitude using Kyoto meteor radar observations made in 1983–1985. Among these oscillations, the quasi-2-day wave is repeatedly enhanced in summer and autumn. We found that the period of the quasi-2-day wave ranges from 52 to 55 h in summer, and becomes as short as 46 to 48 h in autumn in 1983 and 1984. The change in the wave period seems to coincide with a decrease in the amplitude of the zonal mean wind. A quasi-2-day wave event was simultaneously observed in January 1984 at Kyoto (35° N, 136°E) and Adelaide (35° S, 138° E), which are located at conjugate points relative to the geographic equator. Amplitudes of the meridional component at Adelaide are approximately four times larger than those observed at Kyoto. Comparison observations clearly show that the meridional component is in phase and the zonal component is out of phase, respectively, implying antisymmetry of the quasi-2-day wave between the northern and southern hemispheres. Relative phase progressions with height are similar between the Kyoto and Adelaide results for both meridional and zonal components, and indicate the presence of an upward energy propagating wave with a vertical wavelength of about 100 km.