On tidal variability and the existence of planetary wave-like oscillations in the upper thermosphere—I. Observations of tidal variability

The evidence for the existence of tidal variability as observed in the meridional thermospheric wind (approx. 300 km height) is presented for a set of eight ionosonde locations (three in the northern hemisphere and five in the southern hemisphere). The data set corresponds to a full year (1984) of hourly values. The detected variability can be seen in the tidal components of the meridional wind. The diurnal and semidiurnal components are spectrally analysed. The quarterly spectra show that the tidal amplitudes oscillate with periods between 2 and 60 days. The more important oscillations have periods from 15 to 3 days. No direct link between solar and magnetic activity indices was detected. Possible reasons for the observed tidal variability are discussed in the light of the current theory developed for the mesosphere and lower thermosphere.     

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere regions—II. The semidiurnal tide

The semidiurnal tidal dynamics of the Antarctic and Arctic mesopause regions (95 ± 15 km) are investigated through comparative analyses of monthly mean tidal wind fields determined from radar measurements at the Scott Base (78°S), Molodezhnaya (68°S), and Mawson (67°S) stations in the Antarctic, and the near-conjugate stations of Heiss I. (81°N) and Poker Flat (65°) in the Arctic region. The main feature common to all stations is the fall equinoctial maximum in amplitude (10–20 m s⁻¹), which is also reproduced by the most recent numerical tidal model. However, the wintertime amplitude growth with height and the shorter vertical wavelengths characterizing the model are features not reflected in the data. There is also a spring equinoctial maximum in the Antarctic data which the model does not reproduce.Examination of interannual variability reveals characteristics similar to those noted in Part I for the mean zonal wind; namely, some degree of year-to-year variability superimposed on apparent long-term decreases of order 0.3–0.5 m s⁻¹ yr⁻¹ (depending on month) in the Southern Hemisphere semidiurnal tidal amplitudes. Numerical simulations presented herein indicate that changes of this magnitude cannot even be induced (via mode coupling) by a change in the mean zonal wind field of order 30%, and are more plausibly explained by a secular change in the tidal forcing by ozone insolation absorption. However, contrary to Part I, the annual mean tidal amplitude is not characterized by any significant secular trend, remaining within the 10.0 ± 2.5 m s⁻¹ range throughout the 1970–1986 period. Analyses of other data sets are required to ascertain confidence in the apparent trend reported here.     

On the role of the 9.6 μm O3 band in the energetics of the mesosphere and lower thermosphere

Radiative cooling and heating in the 9.6 μm O₃ band has been calculated for the 50–105 km region. The NLTE effects due to the excitation of the ozone ν₃ vibrations by atmospheric and solar radiation and by the release of chemical energy into vibrations upon recombination of O + O₂ into O₃ have been taken into account. It is shown that the LTE approximation is good for altitudes below 70 km where fundamental transitions comprise the main contribution to the cooling rate. Above 70 km, the contribution of the hot transitions to radiative cooling may exceed the contribution of the fundamental ones. In the presence of chemical excitation, part of the chemical energy radiates in the hot transitions, resulting in an additional cooling rate of about 0.5 K/day at 90 km. A method of parameterizing radiative heating which is based on the separation of the effects of fundamental and hot transitions in the 9.6 μm O₃ band is proposed.     

Meteorological effects in the variations of ionospheric parameters—I. The lower thermosphere

The influence of the troposphere and stratosphere on variations of ionospheric D-region parameters are discussed. It is found that variations of the minimum observable ionosonde frequency (f_min) and horizontal winds are closely related to temperature and pressure fields in the lower atmosphere. Experimental data for the Central Asian and East Siberian U.S.S.R. regions have been used.     

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere regions—I. The prevailing wind

The dynamics of the Antarctic and Arctic mesopause regions (ca. 95 ±15 km) are investigated through comparative analyses of winds measured by radars at the Scott Base (78°S), Molodezhnaya (68°S), and Mawson (67°S) stations in the Antarctic, and the near-conjugate stations of Heiss I. (81°N) and Poker Flat (65°N) in the Arctic region. The data were analyzed specifically to delineate hemispheric differences in mean monthly prevailing wind climatologies, and show the circulation systems in the Arctic and Antarctic mesosphere and lower thermospheres to exhibit significant asymmetries. These asymmetries may be attributable to hemispheric differences in dynamical forcing due to one or more of the following: insolation absorption by ozone, other mesospheric heat sources such as exothermic chemical reactions, tropospheric forcing of vertically or obliquely propagating gravity waves which engage in mesospheric mean-flow interactions, and dissipation of planetary waves which find ducting channels through the middle atmosphere.Interannual variability is also examined in the Molodezhnaya and Heiss I. data, which cover the periods 1967–1986 and 1968–1985, respectively. Accompanying significant year-to-year variability, eastward winds at 95 km over the Antarctic (Molodezhnaya station) exhibit a trend of decreasing amplitude from 1968 to 1977 that is not reflected in the Arctic data (Heiss I.); for instance, the annual mean wind decreases in a monotonie sense from 20–25 to 5 m s⁻¹ during this period. It cannot be unambiguously established whether this trend represents a decrease in intensity accompanying secular changes in thermal forcing, or a latitudinal contraction or shifting of the mesospheric jet system. The annual mean winds at Molodezhnaya remain at the 4–8 m s⁻¹ level from 1977 to 1986.In addition, existing empirical models are evaluated against the data, and are shown to be deficient in reproducing some salient characteristics of the high-latitude circulation systems. This latter result especially questions the common practice of deriving winds based on the geostrophic approximation in this altitude/latitude regime.     

Neutral density cells in the high latitude thermosphere—1. Solar maximum cell morphology and data analysis

A new high latitude thermospheric neutral density structure has been revealed in NCAR-TIGCM simulations at 120–350 km altitude. The structure consists of density cells above 50° latitude with radii of approximately 1000 km. There are between two to four cells present depending on the altitude and magnetic activity. For example, at 200 km under magnetically active conditions, the density structure consists of four cells: low density cells are located near dawn and dusk and high density cells are located near noon and midnight. Density variations among the cells range from 5 to 50% for magnetically quiet and active conditions respectively. The cells are present at all seasons, for a wide range of magnetic activity levels, and at solar minimum and solar maximum. The density cell morphology is established for equinox solar maximum as a function of altitude and magnetic activity. Departures of the cell structure from this morphology due to seasonal and solar cycles are discussed. The cell morphology provides a new framework in which to interpret lower thermospheric density data. Data to test and confirm the model predictions were provided by the SETA-1 satellite.     

Performing the global through the local—globalisation and individualisation in the spatial practices of young East Germans

This paper aims to show how young people in former East Germany respond to the globalising processes that are part of the transformation of their society from a state-socialist to a capitalist one. It focuses particularly on the differential ways in which young people perform their identities as global/local subjects through the uses that they make of urban space. While emphasising the agency of young people, the paper seeks to examine the dialectic between globalising forces that are largely beyond their control and the negotiation of these forces in everyday practices of identity-formation. Conceptually, the paper draws particularly on the work of Beck (2000) Beck, U. 2000. “What is Globalization?”. Cambridge and Oxford: Polity Press.  [Google Scholar], Beck and Gernsheim (2002) Beck, U. and Beck-Gernsheim, E. 2002. Individualization. Institutionalized Individualism and its Social and Political Consequences, London: Sage.  [Google Scholar] and Giddens (1994) Giddens, A. 1994. Modernity and Self-Identity. Self and Society in the Late Modern Age, Cambridge: Polity Press.  [Google Scholar] in order to conceptualise the connections between globalisation and individualisation, as well as on feminist and recent geographical work on performativity (Butler, 1990 Butler, J. 1990. Gender Trouble. Feminism and the Subversion of Identity, London and New York: Routledge.  [Google Scholar], 1993 Butler, J. 1993. Bodies that Matter. On the Discursive Limits of ‘Sex’, London and New York: Routledge.  [Google Scholar]; Rose, 1996 Rose, G. 1996. “As if the mirrors had bled: masculine dwelling, masculine theory and feminist masquerades”. In BodySpace: Destabilising Geographies of Gender and Sexuality, Edited by: Duncan, N. 56–74. London and New York: Routledge.  [Google Scholar]; Gregson and Rose, 2000 Gregson, N. and Rose, G. 2000. ‘Taking Butler elsewhere: performativities, spatialities and subjectivities’. Environment and Planning D: Society and Space, 18(4): 433–452. [Crossref], [Web of Science ®] [Google Scholar]; Thrift, 1996 Thrift, N. 1996. Spatial Formations, London: Sage.  [Google Scholar]; Dewsbury, 2000 Dewsbury, J.-D. 2000. ‘Performativity and the event: enacting a philosophy of difference’. Environment and Planning D: Society and Space, 18(4): 473–496. [Crossref], [Web of Science ®] [Google Scholar]; Dewsbury and Naylor, 2002 Dewsbury, J.-D. and Naylor, S. 2002. Practicing geographical knowledge: fields, bodies and dissemination. Area, 34(3): 253–260.  [Google Scholar]) in order to gain an embodied understanding of the ways in which individuals construct themselves as global/local subjects.     

A numerical study of the lunar tide in the mid-latitude F2-region of the ionosphere—II. Oscillations of the ion and neutral gas velocities

The drift due to the lunar electric field which is communicated from the ionospheric E-region causes a re-distribution of the electron density and a neutral air motion in the F2-region. The lunar tide in the electron density of the F2-region due to the lunar electric field has been obtained and discussed in Part I. The lunar tides in the ion and neutral velocities which are obtained in the same way are dealt with in this paper. It is found that the lunar tidal oscillations in the drifts and neutral winds markedly depend on the solar time, and that the amplitude and phase in the x-component of the drift averaged over the solar times are 10.1 m s⁻¹ and 2.6 h and those in the x-component of the neutral wind are 4.6 m s⁻¹ and 4.3 h, respectively, at 45.0° dip.     

Electric fields and currents in the equatorial electrojet deduced from VHF radar observations—II. Characteristics of electric fields on quiet and disturbed days

Using the Doppler spectra of VHF radar signals, the height profiles of the phase velocity (V_p) of 2.7 m irregularities in the equatorial electrojet (EEJ) over Thumba (dip: 56′S) are obtained. The day-time east-west electric fields (E_y) are deduced by matching experimentally observed V_p profiles with theoretically deduced ones for a number of quiet and disturbed days. The experimental E_y values show: (i) a large day-to-day variability; (ii) a large decrease in the afternoon hours on some days (quiet and disturbed); (iii) the frequent presence of short period fluctuations with amplitudes of 30–50% of the background value and with typical time scales of 30–60 min, on moderately disturbed days (9 ⩽ A_p ⩽ 30); (iv) a significant decrease of the average E_y on disturbed days compared to that on quiet days during 0900–1200 h L.T.     

Lidar observation of sudden increase of aerosols in the stratosphere caused by volcanic injections—II. Sierra Negra event

A striking disturbance in stratospheric aerosols over Fukuoka was observed by Nd-YAG laser radar in December 1979. It began with the appearance of a thin layer of enhanced scattering at an altitude of about 17 km and revealed remarkable variations of the layer in time and height. Measurements at two wavelengths suggest that the aerosols changed in size distribution, and the disturbance is inferred to be due to the Sierra Negra eruption. The integrated aerosol backscattering above the tropopause reached about 8 × 10⁻⁵sr⁻¹; i.e. some six times that of the Soufrière event when converted to the ruby wavelength. The mean meridional transport speeds of the dust clouds were much larger than ever observed previously and this may be due to the activation of meridional transport associated with the Canadian sudden stratospheric warming in November-December 1979     

The investigation of electromagnetic interactions between regions surrounding the Earth—1. Initial equations,the boundary conditions,the distribution of external currents and the methods of numerical solution

A numerical model is presented suitable for the study of the penetration of the global atmospheric electric field from the troposphere into the ionosphere. Equations are obtained in the plane-stratified approximation which permit us to use the same mathematical techniques in the atmosphere, the ionosphere and the magnetospheres. We take into account the anisotropy in the general case, the variation of conductivity of the medium and the temporal changes of the fields. The relationship between the electric and magnetic modes is taken into account by means of Ohm's law in anisotropc media, using the electrical conductivity sensor. The feasibility of the plane-stratified approximation is analysed by means of the analogous equations taking into account the spherical symmetry of the global electric field. Models of the external current distribution are discussed. The boundary conditions take into account the field attenuation into the conducting Earth and the field propagation into the magnetosphere as Alfven and magneto-acoustic waves. The methods of numerical solution of the equations obtained and their accuracy are described in brief.     

Communications,Qajar Irredentism and the Strategies of British India: The Makran Coast Telegraph and British Policy of Containing Persia in the East (Baluchistan)—Part II

Persian territorial designs in Baluchistan clashed with British interest to construct an Indo-European telegraph line through the Makran Coast, where Britain had close local allies in dispute with Persia. The British prime interest being the speedy construction of the line, they decided on bypassing these disputed territories by connecting Bushehr, through submarine cable, with Gwadar—which they believed, contrary to the Persians, to be non-Persian. The Persian government protested against the British infringement of her sovereign rights, adopting both diplomatic and military approaches. This forced the British government to check the legality of the Persian claims. But the arbitrary was neither neutral nor fair, with Britain opposing the suzerainty of Persia over the chiefs of western Makran, while acknowledging the right of conquest by others elsewhere on the coast. This was in line with British policy of favoring governments bordering British India over Persia. Although unable to change the arbitrary, the Persian government still managed, in spite of her military weakness, to drag the British government into a hard bargain and tough negotiations.     

Saxon T. Bisbee: Engines of Rebellion—Confederate Ironclads and Steam Engineering in the American Civil War

Journal of Maritime Archaeology -