Characteristics of field-aligned E-region irregularities over lioka (36°N), Japan—I

Measurements with a 25 MHz radar over Iioka, Japan show that field-aligned E-region irregularities occur mainly at night in association with E_s-layers at an altitude range of about 100–110 km and drift predominantly westward with speeds of the order of 60 m s⁻¹. These observed characteristics of the irregularities are shown to be in reasonable agreement with quantitative predictions of the gradient drift instability theory. The predictions are based on appropriate models for neutral air densities and temperatures, ionic composition and ionospheric electric fields and on available observations of electron density profiles of E- and sE_s-layers.     

Effects of ionospheric irregularities on radio waves—II. Group path changes

The effects of ionospheric irregularities on the group path of radio waves reflected at vertical incidence are studied using model irregularities. The basic approach used is quite general in that irregularities and background ionospheres of arbitrary shape may be considered. The method is demonstrated by the use of simple triangular shaped irregularities. For the ionospheric conditions considered irregularities below X ∼ 0.85 have relatively little effect on the group path of ordinary rays. Irregularities extending above this level produce large effects partially due to the rapid variation of the group refractive index near reflection. High gradients produced by irregularities, particularly near reflection, can also be regarded as causing large group path effects. The effect of irregularities near the reflection level is not as dramatic in the extraordinary ray case because the refractive index does not change as rapidly near reflection as it does in the ordinary ray case. When the reflection height is changed by the irregularity the situation is complex because different effects produce opposing changes in the group path. The result is that an irregularity of a given percentage increase in intensity has a maximum positive effect on the group path when it is positioned so that it extends up to reflection without causing reflection height variations. Its maximum negative effect occurs when maximum reflection height lowering takes place. The group path change produced by an irregularity is dependent on irregularity intensity, thickness and background gradient but is least sensitive to intensity. This is in contrast to the phase path changes which are very dependent on background gradient and irregularity intensity but not on thickness. Possible applications of the results to swept frequency group path experiments are discussed and some examples are given.     

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.     

Tidal winds at mesopause altitudes over Arecibo (18°N, 67°W), 5–11 April 1989 (AIDA '89)

An imaging Doppler interferometer (IDI) radar was operated during the three AIDA '89 campaigns in Puerto Rico over the period March–May of 1989. The output of the IDI analysis characterizes radar scattering in terms of a number of discrete ‘scattering points,’ also referred to as ‘multiple scattering centers,’ IDI/MSC for short. For each of these points the three-dimensional location, radial velocity and amplitude and phase are determined, similar to the output of meteor radars. We have applied the conventional Groves [(1959) J. atmos. terr. Phys. 16, 344–356] meteor wind radar analysis to the scattering points to produce the mean apparent motions over the height range from 70 to 110 km which are presented here. The mean apparent motion of the scattering centers is the quantity that would correspond to the neutral atmosphere wind or bulk motion if the scattering points are physical entities (such as turbulent eddies) whose motions are determined solely by advection. This is the quantity which is treated as the ‘wind’ in the analysis which follows and which should be compared to the wind measurements as deduced from the other methods employed during this campaign. There is, however, a caveat which supports the contention of Hineset al. [(1993) J. atmos. terr. Phys. 55, 241–287] that extreme care must be used in interpreting the velocities measured by partial reflection radars as winds. The current application of the Groves method of analysis has revealed motions from which one would infer a typical equatorial easterly circulation, with mean meridional circulation becoming significant only above 96 km. A periodogram analysis of the complete data interval (5–11 April) has shown the diurnal tide to be the most significant feature of the wind field at these altitudes, with zonal amplitudes up to some 50 m/s and meridional amplitudes approximately half this value. The 12 and 6 h tides become as significant as the diurnal above 100 km. The two day (48 ± 5 h) wave is the next most significant feature, with zonal amplitude increasing with height up to 30 m/s at 110km. The semidiurnal tide is not at all well developed below 100 km. However, analysis on a day by day basis reveals a significant semidiurnal component which is not phase coherent over the total interval. Mean vertical velocities are of the order of tens of centimeters per second and are considered to be more realistic than the meters per second velocities usually inferred from analyses of meteor trail drifts.     

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.     

Tidal winds in the radio-meteor region over Trivandrum (8.5°N, 77°E)

Wind measurements using a meteor trail radar which performed during two June solstice and three December solstice months were analysed to study the tidal winds over Trivandrum (8.5°N). The ter-diurnal (8 h) component of wind was found to be as significant as the diurnal and semi-diurnal components. The modulations in the altitude profiles of amplitude and phase of the tidal wind components are interpreted to be due to higher order tidal modes. The amplitudes and vertical wavelengths of the tidal modes observed in the meteor zone are discussed.     

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.     

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.     

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.     

Dynamics of the upper middle atmosphere (80–110 km) at Tromsø (70°N) and Saskatoon (52°N), June–December 1987, using the Tromsø and Saskatoon MF radars

A real-time-winds (RTW) system from Saskatoon operated with the Tromsø MF (partial reflection) radar system on a continuous basis in the period June–December 1987. This interval includes MAC/SINE and EPSILON. Profiles with 3-km resolution were obtained every 5 min—weak ionization and few geomagnetic disturbances limited the observations normally to 80–110 km. However, daily mean winds, diurnal and semidiurnal tidal characteristics (amplitudes, phases and wavelengths) and gravity wave characteristics (intensities, mean directions) are available throughout this interval. This is particularly valuable in defining the background state for some experiments, e.g. rockets, and for comparison with related parameters from the lidar and other radars (EISCAT, SOUSY-VHF). Comparisons with these dynamical parameters from Saskatoon (52 N) are made : the zonal circulation was weaker at Troms0, tidal amplitudes smaller, and summer 12-h tidal wavelengths shorter ( ~ 80 km vs ~ 100 km). The fall transition for this tide occurred in September at Troms0, earlier than observed elsewhere.     

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.     

Combination of Primrose Lake (54°N, 110°W) ROCOB winds (20–60 km) and Saskatoon (52°N, 107°W) M.F. radar winds (60–110 km): 1978–1983

Comparisons are made between data from the unique Saskatoon medium frequency radar set, which is continuous from mid 1978–1983 and the ROCOB data from Primrose Lake, which is only 340 km northwest of Saskatoon. Until 1981 there were 2–3 firings per week and now there are 4–5 per month. While the final agreement is satisfactory, special care was required when matching the two regions: particular problems are the low rocket sampling rate and the unexpectedly large amplitude of the diurnal tide. Combination of the two data sets is made.The Canadian zonal winds are quite similar to CIRA 72, especially in the summer months, however, the winter winds show much more systematic variability due to 12- and 6-month periods of oscillation and stratwarms. Canadian meridional winds differ significantly from existing data models.     

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.     

Drifting patches of equatorial spread-F irregularities—experimental support for the spatial resonance mechanism in the ionosphere

The spatial resonance mechanism which sets in when the plasma drift velocity matches the phase velocity of atmospheric gravity waves in the ionosphere is applied to explain large-scale structures of the equatorial spread-F. The resonance condition is examined for reasonable parameters of travelling ionospheric disturbances, plasma drift and neutral wind velocities. It is shown that the resonance condition can be fulfilled in equatorial regions during the post-sunset hours. The measured drift velocities of patches of range-type equatorial spread-F are similar to measured plasma drift velocities. Some spread-F structures observed with the RTI-technique at Jicamarca, range-type spread-F observed on ionograms of Huancayo as well as the occurrence of spread-F patches observed with transequatorial propagation experiments do occur after the vertical plasma drift reverses from upward to downward. The periods, wavelengths and velocities of the large-scale structure of the spread-F patches appear to be similar to those parameters for medium-scale TID's. It is argued that a non-linear break-up of resonance-steepened TID's gives rise to the quasi-periodic structures which are typical for the range-type equatorial spread-F.     

The Forces of Homology—Hirohito,Emperor of Japan and the 1928 Rites of Succession

In November 1928, Hirohito became the emperor of Japan through a series of rituals, beginning with the emperor's presentation to the world. Afterwards the emperor soul, transmitted from the sun goddess through the preceding generations of emperors to the current one, is rejuvenated and pacified by attaching different gods (kami) to it. Then, in his full presence as a living-kami, the new emperor enters a finely balanced structure to partake of sacred rice with the kami. Within the Japanese cosmos, the world at large, the domain of humankind, and the realm of the kami are situated along a continuum. In such a world, the forces of homology can, through meticulous ritual, connect between those realms and harness one plane for the improvement and augmentation of another. By means of the rites of succession, the emperor activates the forces of homology, yielding a dynamic yet precarious world, as the kami forces of peace and harmony are harnessed for the well-being of all Japan.     

Legends of the Lincolnshire Cars.—Part II

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The Book of Wonder Voyages. Edited by Joseph Jacobs. Illustrated by John D. Batten. London: D. Nutt, 1896.

The North-Western Provinces of India, their History, Ethnology, and Administration. By W. Crooke. London : Methuen &; Co., 1897.

The Popular Religion and Folklore of Northern India. By W. Crooke, B.A. 2 vols. New Edition. Westminster: Archibald Constable &; Co., 1896.

Greek Folk-Poesy. Annotated Translations from the whole Cycle of Romaic Folk-Verse and Folk-Prose. By Lucy M. J. Garnett. Edited, with Essays on the Science of Folklore, Greek Folkspeech, and the Survival of Paganism, by J. S. Stuart-Glennie, M.A. 2 vols. London : David Nutt, 1896.