Inter-relations between current and electron density profiles in the equatorial electrojet and effects of neutral density changes

A simple model of the equatorial electrojet is used to try to reproduce observed current density profiles and it is found that an increase in neutral density is required. The effects of neutral density changes of various kinds are investigated. Changes in the electron density profile due to the j × B force are found to be fairly small and, in the cases studied here, are decreases at all heights.     

Lunar and planetary influences upon the peak electron density of the ionosphere

Observable effects of semidiurnal tidal character caused by the Sun (radiation and gravity) and Moon (gravity only) seem to be influenced by the planet Jupiter and, during approach, by Venus. These effects can be identified during summer for suitably selected planetary configurations. The importance of the lunar effect is found to depend on the solar hour, season and planetary constellation.     

Power spectra of VHF intensity scintillations from F2- and E-region ionospheric irregularities

An experiment is described for the routine study of scintillations and ionospheric irregularities at high-latitudes using NNSS satellites with additional coordinated observations by means of the EISCAT ionospheric radar facility. Early results, obtained during the development phase of the experiment, are presented of the power spectra of intensity fluctuations at 150 MHz observed at the equatorwards edge of the high-latitude irregularity zone. The spectra of 165 samples of night-time scintillation recorded during October 1982 to May 1983 show a spectral index with a mean value of −3.58 and a steepening of the spectral slope with increasing S₄. Some examples of scintillation arising from irregularities at E-layer height show spectral indices of magnitude generally smaller than for F-region cases. A few spectra have been found with a clear break in spectral slope at around 10 Hz, suggesting two regimes for irregularities of different scale sizes.     

Diurnal variations in F2 peak density and ionization flux above Tahiti

The effects of composition and ionization fluxes on the diurnal variation of NmF2 at an equatorial anomaly zone station (Tahiti) are separated. The calculated diurnal variation of the fluxes agrees well with what would be expected from published equatorial E × B drift observations and global neutral wind models. A correlation analysis shows that lower hmF2 is often accompanied by larger NmF2, in spite of a much larger recombination rate. This illustrates the dominance of the fountain effect and neutral wind induced interhemispheric transport at this station.     

Observations of ion layer motions during the AIDA campaign

The AIDA-89 campaign has yielded the most comprehensive set of low-latitude incoherent scatter radar power profiles and derived electron concentration results ever made. These results have been used to study the time-height trajectories of 80–150 km ion layers and serve to gauge both the periodicity and variability of ion layer structure throughout the campaign. Features of the AIDA ion layer trajectories point to a dynamics ‘zoo’ of processes ranging from multiday-period waves, tides and acoustic-gravity waves (AGWs) to geomagnetic storm effects and evidence of coupled neutral sodium and ion layer/plasma processes. The semidiurnal and diurnal tides are evidenced in the almost always present layers, the Tidal Ion Layers (TILs), which are identified by their regular and periodic trajectories that also display regions of variable mixing or confluence of the various tides. The TILs are contrasted with the truly sporadic layers that include sporadic E and sporadic intermediate layers. The sporadic layers may be formed due to interaction of the tidal wind system with AGWs. The formation process may involve horizontal as well as vertical ion convergence mechanisms and/or various non-linear effects. Limits to the study derive from volume undersampling due to use of the single radar beam.     

A comparison of the height of the maximum electron density of the F2-layer from real height analysis and estimates based on M(3000)F2

Estimates of the height of the F-layer peak based on formulations using the ionospheric transmission factor M(3000)F2 are compared with hmF2 derived from the real height analysis of digital ionograms acquired at a mid-latitude station. Based on the analysis of 27 hours of quiet data, our result shows that the M(3000)F2 methods are highly accurate and that the formulation developed by Bradley P. A. and Dudeney J. R., (1973, J. atmos. terr. Phys. 35, 2131) is most accurate.     

Magnetic field of the magnetospheric ring current and its dynamics during magnetic storms

This review examines models existing in the literature which describe the magnetic field produced by the ring current (DR) at the Earth's surface based on the energy balance equation. The parameters of this equation, the injection function F and decay parameter τ are considered to depend on parameters of the interplanetary medium and the DR intensity. The existing models are shown to be able to describe the DR variations with sufficient accuracy (r.m.s. deviation δ between the experimental and modelled values of DR for 170 magnetic storms is 5 < δ < 15 nT and the correlation coefficient between the two is 0.85 <r<1). The models describe that part of the geomagnetic field variation at low latitudes during a magnetic storm that is controlled by the geoeffective characteristics of the interplanetary medium and which thus responds immediately to its variations (the driven part).The values of τ are significantly less during the main phase of a magnetic storm than during the recovery phase. This reflects the difference in the main mechanisms of ion loss from the ring current during the two phases of the storm. These are the interaction of ions with hydromagnetic waves during the main phase of the storm with its intervals of intense plasma injection into the inner magnetosphere and charge exchange with the cold hydrogen geocorona during the recovery phase.     

Aircraft measurements of the geomagnetic latitude effect on air-earth current density

Recent investigations of the electrode effect and the phenomenon of bubble electrification processes at the air-sea interface throw doubt on the applicability of using surface atmospheric electric observations made at sea by the Carnegie for proving the latitude effect in the columnar resistance of the atmosphere. Conduction current measurements were taken on flights during a period of decades by two instrumented aircraft in oceanic areas remote from sources of pollution. A composite of these measurements is given and confirms the notion that there is a latitude variation in air-Earth current. With the reasonable assumptions of an equal ionospheric potential and either low concentrations of Aitken nuclei or at least suitably small variations in their density with respect to latitude, the observed variation is apparently the integrated result of the Earth's magnetic field acting on cosmic ray activity throughout the troposphere.     

Anthropocene and the dawn of a planetary civilization

This exploratory article invites anthropologists to renew their curiosity about the human condition and creatively decode today's contemporary myth-making practices. After a decade of active academic engagement with the Anthropocene, we would do well to turn our endless curiosity about the world and its diversity to the Promethean stories ecomodernists are spreading with accelerated ease within the public sphere. To burst out of our media-saturated environment, the author asks: what patterns of deglobalization and reglobalization will emerge from the stories we tell each other about the Covid-19 pandemic and the health of the planet? In what ways do these stories inform us about the society we want to create, inhabit and pass on? The author shows how redeploying our skills as storytelling analysts and ethnographers of embodied and collective experiences helps us to renew questions about place and mobility. As we enter a new era of symbolic manipulation, remembering the importance of myths may help us contribute to the emergence of a planetary civilization that the earth appears to be calling for.     

Vertical neutral wind in the equatorial F-region deduced from electric field and ion density measurements

DC electric field and ion density measurements near density depletion regions (that is, equatorial plasma bubbles) are used to estimate the vertical neutral wind speed. The measured zonal electric field in a series of density depletions crossed by the San Marco D satellite at 01.47-01.52 UT on 25 October 1988, can be explained if a downward neutral wind of 15–30 m s⁻¹ exists. Simultaneously, the F-region plasma was moving downward at a speed of 30–50 m s⁻¹ These events appear in the local time sector of 23.002&#x0304;23.15 in which strong downward neutral winds may occur. Indeed, airglow measurements suggest that downward neutral velocities of 25–50 m s⁻¹ are possible at times near midnight in the equatorial F-region.     

Incoherent scatter radar measurements of electron density and ion velocity during an isolated substorm

A study of the average pattern of F-region plasma densities and velocities measured by the Chatanika incoherent scatter radar has previously suggested that the main ionospheric F-region trough is formed in the evening sector by the westward transport of plasma under the influence of convective electric fields. This paper examines the role of convective electric fields on the electron density profile and the formation of the F-region density trough for a particular night. Incoherent scatter radar data from Chatanika are presented.On 25 May 1972 an isolated substorm occurred near 0900 UT after a long period of magnetic quiet. The substorm was manifested at Chatanika, in the evening sector, by a small positive bay and a concurrent onset of westward motion of plasma associated with a rapid decrease in the F-layer electron density in the region of the moving plasma. Analysis of plasma densities and velocities during this event indicates that

• 1.(1) temporal changes of plasma motion are associated with changes in the convective electric field pattern in response to substorm activity
• 2.(2) the electric field pattern created a north-south gradient in the F-layer electron density which is interpreted as the formation of the ionospheric trough near its equatorward edge, and
• 3.(3) large scale electron density fluctuations were observed in the evening sector resulting from westward travelling density variations originating in the midnight sector.

The study emphasizes the complexity, and difficulty in interpretation, of single station auroral zone measurements of the F-region ionosphere.     

The relationship between school ground design and intensity of physical activity

In this study, we investigated the relationship between school ground design and children's physical activity levels. In particular, we were interested in understanding the contribution of ‘green’ school ground design to physical activity levels. Data for this study were collected at an elementary school in Australia and in Canada. At each school, scans of Target Areas were completed to record the students' location and intensity of physical activity, based on the System for Observing Play and Leisure Activity in Youth (SOPLAY) (Australia: 23 scans, 6 Target Areas; Canada: 18 scans, 7 Target Areas). At both schools, the highest percentage of children present was engaged in vigorous physical activity on the manufactured equipment (42% of children/scan). Similarly, at both schools, the green area encouraged the highest percentage of children present to be engaged in moderate physical activity (47% of Australian children/scan, 51% of Canadian children/scan). The patterns of sedentary behavior differed slightly between countries. At the Australian school, the paved sporting courts (57%) and the paved canteen courtyard (50.5%) promoted the highest degree of sedentary play. At the Canadian school, the treed grassy berm (42%) and the treed concrete steps (43%) encouraged the highest percentage of sedentary behavior, followed by the open asphalt (34%). These results are also discussed in light of gender distribution. We conclude with a discussion of the design and cultural factors that influence children's physical activity on school grounds. We argue that if school grounds are to realize their potential to promote physical activity, they should include a greater diversity of design features and ‘green’ elements that engage children of varying interests and abilities in active play.     

Parachute measurements of positive ion density of the middle atmosphere over the dip equator by spherical probe

A parachute-borne gridded spherical probe has been used to measure the total positive ion density. Two launches were made, using Soviet M-100 rockets, on 22 and 29 April 1987, at 1200 UT, from an equatorial station, Thumba (8°N, 76°E) India. Data were obtained for the altitude region 10 to 80 km. A broad maximum around 15 km and a broad minimum around 60 km have been noticed in the ion current profiles obtained in both flights. The theory of the operation of the probe has been given. A detailed discussion of the results obtained has also been included.     

Field-aligned and field-perpendicular velocities in the ionospheric F2-layer

Incoherent scatter observations have shown that there is sometimes a detailed anticorrelation or ‘mirroring’ between V_∥ and V_⊥, the components of F2-layer plasma velocity parallel to and perpendicular to the geomagnetic field. In this paper we develop a simple theoretical model of the F2-layer and compute its response to applied perturbations of V_⊥, both steplike and oscillatory; in particular we investigate the phase and amplitude relationships between V_∥ and V_⊥ resulting from ion-drag and plasma diffusion. For periods of a few hours, the oscillations of V_∥ lag behind exact anticorrelation with V_⊥ by 0.1–0.2 cycle, but the time lags corresponding to these phase differences are only a fraction of 1 h and seem broadly compatible with observations previously reported from Arecibo and Malvern. We do not study the question of what causes the velocities to fluctuate in the first place.     

SO2F2用于熏蒸经书字画的探讨

对于书画纸张害虫的防治,国内外普遍应用的方法有化学杀虫法(胃毒、接触、熏蒸)和物理杀虫法(高温与低温、γ射线辐射、气调)。由于物理杀虫法需要一定的仪器设备使之创造苛刻的局部环境,致使广泛应用受到了应有的限制。我国目前在图书档案、古籍字画害虫的除治中,化学杀虫法使用率最