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.     

A numerical model of the ionospheric dynamo—I. Formulation and numerical technique

A new method of numerically solving a suitably formulated ionospheric wind dynamo equation for electrostatic potential and field is developed. Unlike in many other dynamo models, the upper boundary does not exist and the formulation asymptotically approaches the equatorial boundary condition. Therefore, it naturally incorporates the symmetric, asymmetric E- and F-region dynamo actions in any given ionosphere and any given global or local wind field. It also enables the equation to be posed as an initial value problem and solved numerically using an efficient, accurate, stable and fast integration method of ordinary differential equations. The numerical technique can be extended to compute three dimensional dynamo-generated electric currents in the ionosphere.     

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.     

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.     

A numerical study of the lunar tide in the mid-latitude F2-region of the ionosphere—I. Oscillations of the electron density

The continuity equations for four ion species and the momentum equations for the ion, electron and neutral gases are solved numerically. The momentum equations for ions and electrons include the effects of the electric field, and that for the neutral gas includes the effects of the collision between ions and neutrals, Coriolis force, the viscosity and the horizontal pressure force. It is found that the calculated semi-monthly tidal oscillations in NmF2 during the day and night-time are almost out of phase to each other, while the phase of the oscillations in hmF2 is weakly dependent on the solar time. The amplitude and phase of the calculated semi-diurnal lunar tide averaged over the solar times are 1.7% and 9.1 h (in NmF2) and 4.6 km and 8.1'h (in hmF2) respectively, at 45.0° dip. The height distribution of the semi-monthly lunar tide in the electron density is also obtained. The results show that the phase is 2 h for the lower region (below 200 km) and shifts to 9 h above about 250 km in the daytime, whereas it is nearly constant with height in the night-time. The calculated results are in good agreement with observations except for the phase at night. Thus it may be concluded that the major features of the observed lunar tidal variations in the mid-latitude F2-region can be explained by the electromagnetic drifts due to the solar and lunar electric fields.     

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.     

The winter anomaly in the ionospheric D-region—some numerical calculations

This paper reports on results of numerical calculations for conditions under which the anomalously high absorption of radio waves appears and disappears at middle atmosphere heights, having characteristic time constants of about 24 h. In the calculations we have solved a system of equations which are self-consistent in a one-dimensional approximation and govern the temperature and neutral and ion composition behaviour in the height range 40–150 km. The values of the turbulent transfer coefficient and turbulent energy dissipation rate were calculated for the case of the anomalous absorption commencement, using experimental data pertaining to the vertical structure of the wind and temperature field. The results derived from numerical calculations involving evidence of turbulent processes were used to interpret some characteristic properties of neutral and charged particles, temperature and densities for day-time conditions with anomalously high absorption. The lack of experimental data on winds and temperature throughout the height range under study for the dates with normal absorption forced us to use indirect measurements in making assumptions about the vertical profile of the turbulent transfer coefficient and the values of the turbulent dissipation rate. The results thus obtained agree with measurements of electron density, temperature and hydroxyl emission intensity (the hydrogen content decreases as the conditions change from anomalous to normal). There are, however, discrepancies between calculated and measured atomic oxygen densities.     

The arts as an instrument? Notes on the controversy surrounding the value of art

In the last decade of the twentieth century a shift occurred in the way western governments defended their cultural policies. New, instrumental arguments were put forward. This collided with the way the arts had learned to see themselves in the twentieth century: autonomous, with a value of their own. This article elaborates this confrontation of the arts and policy in two ways. First, it is shown that the distinction between an instrumental and an intrinsic value of the arts originates in a misperception of recent history. It was the political constellation of the Cold War that made governments in the second half of the twentieth century support the arts to be free and independent. Next, an attempt is made to anchor the value of art in a unique kind of instrumentality. With the help of philosophers and historians of culture, it is argued that the arts should be considered instruments of experience.     

The breakdown of the educational system of the G.D.R. in 1989—Problems of restructuring public education

The disappearance of an apparently well-established European state within one year—sudden, unexpected, and self-imposed—probably presents an event without parallels in European history. In educational history, too, there may be few examples of bringing together the structures of two very different educational systems after four decades of separate development.     

One world? Many worlds? The place of regions in the study of international society

This article is a revised version of the 2006 Martin Wight Memorial Lecture and examines the placeof regional states‐systems or regional international societies within understandings of contemporary international society as whole. It addresses the relationship between the one world and the many worlds‐on one side, the one world of globalizing capitalism, of global security dynamics, of a global political system that, for many, revolves a single hegemonic power, of global institutions and global governance, and of the drive to develop and embed a global cosmopolitan ethic; and, on the other side, the extent to which regions and the regional level of practice and of analysis havebecome more firmly established as important elements of the architecture of world politics; and the extent to which a multiregional system of international relations may be emerging. The first section considers explanations of the place of regionalism in contemporary international society and the various ways in which the one world aff ects the many. The second section deals with how regionalism might best be studied. The final section analyses four ways in which regionalism may contribute to international order and global governance.     

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.     

The amplitude of auroral backscatter—I. Model estimates of the dependence on electron density

A model of the auroral backscatter amplitude, in the form discussed by Uspensky and Oksman et al., has been derived for the radar geometry appropriate to joint observations by the PGI auroral radars at Karmaselga and Essoyla and the EISCAT incoherent scatter radar. The model shows how refraction effects cause a strongly non-linear dependence of backscatter amplitude on electron density in the E-region. It also explains why the macro aspect sensitivity for auroral radar operating at a frequency of about 45 MHz is only 1–2 dB per degree for aspect angles greater than 5°.