Upper atmosphere semidiurnal tides at Christchurch (44°S) and Scott Base (78°S)

Lunar and solar semidiurnal tides have been determined from winds measurements in the 82 to 100 km height range at Christchurch and Scott Base made during 1983–1984. At Christchurch, the solar tide has maximum amplitudes in April and December, while at Scott Base, only the December maximum is present at all heights. Phases at Scott base mostly agree with those measured earlier at Mawson, but vertical wavelengths are always long. The lunar tide was difficult to isolate at Christchurch, but the winter to summer phase reversal was clear. This was also seen at Scott Base.     

Observations of the quasi 2-day wave near 90 km altitude at Adelaide (35°S)

A quasi 2-day oscillation in the meridional winds near 90 km altitude has been observed at Adelaide (35°S) during late summer of the years 1966–1975. The mean amplitude in mid-January is 48 m s⁻¹, and the phase variation with height is indicative of a wave with downward phase propagation and a vertical wavelength greater than 100 km.     

Total electron content of the ionosphere at 31°S, 1967–1974

The total electron content (TEC) of the ionosphere at 31°S (geographic) has been calculated on the basis of Faraday rotation measurements made between September 1967 and January 1975 using geostationary satellites. The day-to-day, diurnal, seasonal and solar cycle variations of TEC are illustrated and discussed in relation to the maximum electron density of the F-layer, NMAX. A regression analysis is used to derive curves corresponding to fixed high and low levels of activity. The variations of slab thickness S = TEC/NMAX are also illustrated and discussed. The results overlap the observation periods of other published results and general agreement is found with these other results.     

OI 630 nm imaging observations of equatorial plasma depletions at 16° S dip latitude

Equatorial ionospheric irregularities in the F-layer have been the subject of intensive experimental and theoretical investigations during recent years. The class or irregularities which continues to receive much attention is characterized by large scale plasma depletions, generally referred to as ionospheric plumes and bubbles. The OI 630.0 nm F-region night-glow emissions arising from recombination processes can be used to observe the dynamics of transequatorial ionospheric plasma bubbles and smaller scale plasma irregularities. In a collaborative project between the Center for Space Physics of Boston University and Brazil's National Institute for Space Research (INPE), an all-sky imaging system was operated at Cachoeira Paulista (22.7° S, 45.0° W, dip latitude 15.8° S), between March 1987 and October 1991. In addition to the imager, photometer and VHP polarimeter observations were conducted at Cachoeira Paulista, with ionospheric soundings carried out at both C. Paulista and Fortaleza, the latter at 3.9° S, 38.4° W, 3.7° S dip latitude. For this longitude, the observed seasonal variation of the airglow depletions shows a maximum from October through March and a very low occurrence of airglow depletions from April through September. This long series of OI 630.0 nm imaging observations has permitted us to determine that when there are extended plumes, the altitudes affected over the magnetic equator often exceed 1500 km and probably exceed 2500 km at times, the maximum projection that can be seen from Cachoeira Paulista. This holds true even during years of low solar flux.     

Initial EISCAT observations of plasma convection at invariant latitudes 70°–77°

The potential of the EISCAT radar system for observing plasma convection patterns at high latitudes has been explored in a preliminary experiment on 27 November 1982. Using a beamswinging technique, plasma velocity was measured at slant ranges of 645–1170 km, enabling velocity vectors to be derived for invariant latitudes 70°–77°. Although operational problems limited the experiment to 80 min, some interesting observations of high-latitude flows were made. Typical afternoon westward flows of about 1 km s⁻¹ were recorded over much of the interval, but important temporal and spatial variations were also seen as a result of the good time and space resolution of the experiment (5 min and 75 km, respectively). In particular, the westward flow was interrupted for about 10 min by a surge of poleward flow, possibly related to dynamic coupling occurring at the dayside magnetopause, such as a flux transfer event.     

Excavations at Stobi, 1973–1974

Abstract

Stobi is an ancient city ca. 150 km. north of Thessalonica in what is now Yugoslavian Macedonia. It lies in the juncture of two important rivers, the Erigon and the Axius, which are known today as the Crna and the Vardar. Excavations since 1970 by the joint American-Yugoslav Stobi Excavation Project have contributed significantly to our understanding of living conditions, social organization, arts, crafts, and religion in Stobi. The excavations have also increased our knowledge of the physical environment, of the external political, commercial, military, and religious relations, and generally of the history of Stobi from the 3rd century B.C. to the late 6th century A.C. Its growth can now be traced from a relatively small but strategic Paeonian and later Macedonian community during the Hellenistic era, to a large and prosperous municipium during the early centuries of the Roman Empire and finally to a provincial capital and episcopal see of the later Empire.     

Simultaneous meteor radar observations at Monpazier (France, 44°N) and Punta Borinquen (Puerto Rico, 18°N). II—Mean zonal wind and long period waves

Meteor radar wind observations have been simultaneously conducted by the CNET/CRPE meteor radar group at Monpazier (France, 44°N) and at Punta Borinquen (Puerto Rico, 18°N) in 1977–1978. The Puerto Rico results yielded some characteristics of the mean zonal wind and long period motions at low latitudes which have been compared with the characteristics of the same components observed at middle latitudes. Some differences (both time and altitude shift) are seen for the winter and spring circulation between low and mid-latitudes and even high latitudes (Kiruna, 68°N) where a CNET radar was established in 1974–1975.More energy was observed at low latitudes in the long period wave range and with the systematic existence of peaks at periods 2.5 days and between 3 and 10 days. The long period motions can be generally considered as ‘evanescent’ waves at low and middle latitudes, except during the July–August campaign in Puerto Rico.The existence of two components of 6-day and 60 h periods at both stations in March 1978 allowed us to assume that these waves were planetary waves and to study their longitudinal and latitudinal structure.     

Atmospheric X-rays at 11°S geomagnetic latitude

X-ray measurements at balloon altitudes were made at São José dos Campos, Brasil (23°12′S, 45°51′W geographic coordinates, ~11°S geomagnetic latitude) on 18 December 1981, using an omnidirectional NaI(T1) scintillation detector. Atmospheric X-rays, namely secondary X-radiation from cosmic rays, were measured for the energy interval 30–155 keV and up to an atmospheric depth of 5.5 g cm⁻². A comparison of the flux measured at the Pfotzer maximum during these measurements with those obtained previously by several research groups at other latitudes and with a similar technique has also been made. Finally, a comparison of the atmospheric component with that attributed to the diffuse component is also presented and it is concluded that both components are of about the same magnitude at ~ 5 g cm⁻² and at ~ 11°S geomagnetic latitude.     

Winds and waves in the middle atmosphere at Saskatoon (52°N, 107°W), Collm (52°N, 15°E) and Badary (52°N, 105°E)

Winds data from three radar systems in the U.S.S.R. G.D.R. and Canada, which are well-spaced along the 52°N latitude circle, are used to illustrate longitudinal/regional variations in the dynamics of the upper middle atmosphere 80–97 km. Responses to the stratospheric warming of 1982/3 are noted at all three locations, but the zonal wind does not reverse at Badary, consistent with the flow there being eastward during all months of the year. Planetary wave period oscillations (2–30 days) are observed at all locations, and highly significant cross-spectral coherences exist between the three stations.     

The characteristics of the mesospheric two-day wave as observed at Grahamstown (33.3°S, 26.5°E)

The characteristics of the quasi two-day wave, as observed in meteor wind data recorded at Grahamstown (33°19′S, 26°30′E) between April 1986 and April 1989, are described and discussed in the context of existing knowledge. As is typical, the wave amplitude has been largest during the summer months December–February with a maximum in late January, but this amplitude has differed markedly from year-to-year. The period and phase are found to be variable and, where possible, have been obtained as functions of date. January 1987 and 1989 were both characterised by clear drifts toward longer periods, with corresponding drifts in phase. At each of the summer maxima observed the period was found to be close to 48 h, with the phase of the meridional component within 3 h of local midnight. Direct comparison of local data for January 1987 with published data obtained simultaneously in Australia and Antarctica confirms the well-established westward propagation of the wave, but with an apparent zonal wavenumber somewhat smaller than the expected value of 3. It is shown that the discrepancy could arise from a combination of observational effects and a northward tilt to the wave velocity. The best result of an attempt to detect a horizontal phase gradient from local data alone is, however, more consistent with a southward tilt. There is theoretical support for both conclusions, but the matter cannot be resolved with the data presently available. It is also concluded that the background circulation at meteor heights has little influence on the wave parameters, and that indications of wave activity outside the summer season are of doubtful significance.     

Thermospheric and mesospheric temperatures during geomagnetic storms at 23°S

Night-time thermospheric temperatures, T63o, and mesospheric rotational temperatures, T(OH) and T(O₂), have been measured at Cachoeira Paulista (23°S, 45°W, 16°S dip latitude), located in both the equatorial ionospheric anomaly and the South Atlantic Geomagnetic Anomaly, with a Fabry-Perot interferometer and a multi-channel tilting filter-type photometer, respectively. The thermospheric temperatures are obtained from the Doppler line broadening of the OI 630.0 nm emission and the mesospheric rotational temperatures from the OH(9,4) and O₂A(0,1) band emissions. Measurements made during three geomagnetic storms showed that the nocturnal mean values of T₆₃₀ during the recovery phase of the storms were lower than those observed during quiet time and from model predictions. Also, the nocturnal mean value of the T₆₃₀ soon after the SSC event on 27 June 1992 was higher than the quiet time and model predictions. The observed mesospheric nocturnal mean rotational temperatures, T(O₂) and T(O₂), were unaffected by the storms. A comparison of the night-time observed temperatures T₆₃₀, T(OH) and T(O₂) with those calculated using the MSIS-86 model is also presented.     

Justified at Last? Kissinger's Cyprus Legacy, 1974–1976

This article focuses on the Cyprus talks between 1974 and 1976. It presents the beneficial role the former US secretary of state, Henry A. Kissinger, played in bringing the Greek and Turkish sides around the negotiating table and commit to the efforts for a mutually acceptable settlement following the 1974 Cyprus crisis. Kissinger acted as the honest broker between Ankara, Athens and Nicosia moderating each side's demands and communicating their respective positions when direct contacts were insufficient. All parties for different reasons welcomed his involvement and considered his presence a necessity necessary. Since the public in Greece and Cyprus remained hostile to him, the US secretary remained on the side-lines. Kissinger offered innovative solutions on controversial questions that prevented progress. Thanks to his contribution intense negotiations between the two Cypriot communities with the support of Greece and Turkey took place during the Ford administration. His intervention could not and did not suffice to overcome domestic conflicts and political considerations that prevailed over the efforts for a reconciliatory and mutually acceptable agreement. Nonetheless, he succeeded in paving the way for reducing tensions in the Eastern Mediterranean.     

Winds oscillations (∼ 6h–6days) in the upper middle atmosphere at Monpazier (France, 45°N, 1°E) and Saskatoon (Canada, 52°N, 107°W) in 1979–1980

The medium frequency radar (∼ 2.2 MHz) at Saskatoon has been run continuously since 1978 and the Meteor Radar at Monpazier ran continuously for ∼ 10 day intervals in most months of 1979/1980. The radars are separated by ∼ 8000 km. Because of the excellent quality of the data, spectral and harmonic analyses have been completed from ∼ 70 to 100km and oscillations with periods of ∼ 6h–6days studied.There are substantial similarities in the mean zonal winds, both with regard to magnitudes and times of seasonal reversals; also in annual and semi-annual oscillations. In general, the semi-diurnal tide has similar amplitudes, phases and vertical wavelengths : there are consistent summer (long λ) and winter (short λ) characteristics, with rapid transitions between them. Differences between the timing of these transitions and in some of the mid-season tides are discussed. The diurnal tide is less regular and of smaller amplitude at both locations, often being too small to reliably characterize at Monpazier. However, seasonal variations between summer and winter months may be discerned.In addition to the 24 and 12 h tidal oscillations, which traditionally are studied in most detail, there is clear evidence for additional osculations near 6,8, ∼ 10 and ∼ 16 h and longer periods of ∼ 2 and ∼ 5 days. The amplitudes of these are often comparable or larger than the ‘dominant’ 24 and 12 h tides. The monthly and seasonal variations of these additional oscillations are studied, as a function of height, at the two locations. There is evidence for large scale (global) and small scale (local) disturbances in the wind field.     

Long period wind oscillations in the meteor region over Trivandrum (8°N, 77°E)

The spectra of long period wind oscillations in the meteor zone over Trivandrum are presented. The spectral amplitudes were found to be much larger during June 1984 when the QBO in the stratospheric zonal wind was in a strong easterly phase compared with June 1987 when the zonal winds at the altitude of maximum QBO were weak westerlies. Zonal wind amplitudes for periods of 15 and 5 days were found to be most significant during these two June months. The amplitudes of these two oscillations in meridional wind were found to be as large as the amplitudes in the zonal wind. The vertical wavelength in both zonal wind and meridional winds of the 15-day oscillation is very large whereas for the 5-day oscillation the vertical wavelengths were 80 and 65 km during June 1984 and June 1987, respectively. The results are discussed.     

Variations of mean winds and tides in the upper middle atmosphere over a solar cycle,Saskatoon, Canada, 52°N, 107°W

Saskatoon (52 N, 107 W) medium frequency (MF) radar data from 1979 to 1990 have been analyzed to investigate the solar activity effects on upper middle atmospheric winds and tidal amplitudes. The period of study covers two solar maxima and a solar minimum; the continuous data allow a systematic analysis of solar cycle dependence on mean winds and tides. The height region of 79–97 km sampled in the study shows an apparent but very weak dependence of mean winds and tidal amplitudes on solar activity variation. The observed features are fairly consistent with the early results reported by Sprenger and Schmindkr [(1969) J. atmos. terr. Phy. 31, 217). The mean zonal wind and the semidiurnal tidal amplitudes appear to exhibit positive and negative correlations with the solar activity, respectively; the statistical significances of these correlations are generally low. There is a biennial periodicity evident in the zonal wind oscillations but this docs not have a consistent phase relationship with the equatorial stratospheric wind oscillations (QBO). The meridional winds and the tidal amplitudes are characterized with different and quite irregular periods of oscillations (2–5 yr). The diurnal tidal variations over the solar cycle are small and irregular, although amplitudes are slightly larger during the solar minimum years.     

Observations of gravity waves from multispectral mesospheric nightglow emissions observed at 23°S

Simultaneous measurements of the 015 57.7 nm, O₂ atmospheric (0,1) band, NaD and OH (9,4) band emissions obtained during the period October November 1989 at Cachoeira Paulista (23°S, 45°W), Brazil, have been analysed to study gravity waves in the mesospheric region at a low-latitude station in the southern hemisphere. It was found that, when these emissions showed large temporal intensity variations, there were also short period quasi-coherent temporal variations superposed on them, suggesting a possible passage of internal gravity waves in the emission layers. Cross-correlation analysis indicates that the time lag between the different emissions is smaller for short period variations compared with the long period variations. The wave parameters, namely a vertical wavelength of 12 km, a horizontal derived wavelength of 200 km with a period of 80 min, estimated from one of the observed short-period coherent oscillations, are typical of the internal gravity waves at the airglow emission height.     

Quasi-biennial oscillation in ionospheric parameters measured at Juliusruh (55°N, 13°E)

When seasonal variations were eliminated by evaluating 12-month running means, the ionospheric parameters foE, foF2 and hmF2 at Juliusruh (54.6°N, 13.4°E) showed large solar cycle variations. However, when further 3-yr running averages were evaluated and subtracted, QBO (Quasi-biennial oscillations) were noticed in all these parameters. Sunspot series did not reveal a QBO, but geomagnetic Ap did show a QBO. The peaks of the ionospheric QBO and QBO of Ap could be roughly compared, with lags or leads of a few months. Also, these compared roughly with the well-known QBO peaks of tropical stratospheric (50 mb) zonal winds. Similar analyses at other locations are warranted.     

Optical interferometer measurements of thermospheric temperature at Kavalur (12.5°N, 78.5°E), India

First results on the behaviour of thermospheric temperature over Kavalur (12.5°N, 78.5°E geographic; 2.8°N geomagnetic latitude) located close to the geomagnetic equator in the Indian zone are presented. The results are based on measurements of the Doppler width of O(¹D) night airglow emission at 630 nm made with a pressure-scanned Fabry-Perot interferometer (FPI) on 16 nights during March April 1992. The average nighttime (2130-0430 IST) thermospheric temperature is found to be consistently higher than the MSIS-86 predictions on all but one of the nights. The mean difference between the observed nightly temperatures and model values is 269 K with a standard error of 91 K. On one of the nights (9/10 April 1992, Ap = 6) the temperature is found to increase by ~250 K around 2330 IST and is accompanied by a ‘midnight collapse’ of the F-region over Ahmedabad (23°N, 72°E, dip 26.3°N). This relationship between the temperature increase at Kavalur and F-region height decrease at Ahmedabad is also seen in the average behaviour of the two parameters. The temperature enhancement at Kavalur is interpreted as the signature of the equatorial midnight temperature maximum (MTM) and the descent of the F-region over Ahmedabad as the effect of the poleward neutral winds associated with the MTM.     

Semidiurnal tidal winds at Collm (52°N, 15°E) and Saskatoon (52°N, 107°W) over the decade 1978–1988

Mean winds and tides have been measured by the LF and MF radar systems at Collm and Saskatoon respectively. Semidiurnal tide amplitudes and phases near 90 km evidence very similar monthly variations. A detailed comparison of mean wind and tidal profiles (85–110 km) in the Septembers of 4 years shows some differences however, which are consistent with regional (Europe-Canada) differences in the mean background winds.