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The International Geophysical Year (1957–1958) was inspired by the realization that much better and more complete information was needed about the Earth and geospace to understandand manage the complete terrestrial environment on which we depend. So it was that the IGY member countries worked together to deploy a large number of geophysical observatories around the world.These nations were pursuing the major IGY objectives to collect geophysical data as widely as possible, and to provide free access to these data for all scientists around the globe.About 50 permanent stations were set up in the Arctic and Antarctic, and the World Data Center System was established to ensure that the data collected were properly archived and made available without restrictions for scientific research and practical applications.

Robert Benson raises interesting points regarding the eGY and the role of world data centers. We share the belief that the WDC system was one of the great achievements of the IGY. We have also supported the many and varied activities of data centers over the years. The eGY is not intended to replace data centers, but rather to enhance them.

An analysis of concurrent Pc 1 pulsation activity (0.2–0.6 Hz) recorded on the ground at Mawson, Antarctica (70°S magnetic latitude (MLAT); 19°E magnetic longitude (MLONG); L=8), and on board the Viking polar-orbiting satellite, when the spacecraft was located near apogee (13.5×10³ km) from 50–77° MLAT above the northern ionosphere, shows that simultaneous pulsations were observed only when Viking's conjugate point was within 60-70°S MLAT and 30°E–33°W MLONG, an extent of about 1000 km in latitude and 1700 km in longitude. Spectral analysis confirms that the waves responsible for these pulsations are electromagnetic ion cyclotron (EMIC) waves that have propagated to the spacecraft and ground from the geomagnetic equator. For the intervals when the waves were on field lines above and equatorward of Mawson, convective EMIC wave modeling shows wave growth is dominant below the equatorial He+ gyrofrequency. Waves generated on field lines poleward of Mawson exhibit frequencies above the equatorial He+ gyrofrequency. These propagate to Mawson, most likely through a purely proton plasma rather than a multi-ion environment. Frequency shifts in the Pc 1 activity at Mawson appear to be directly linked to solar wind velocity and flux variations measured by IMP 8. For certain intervals these linked observations are consistent with an interpretation based on the velocity and flux changes altering the radial position of the magnetopause through pressure balance considerations. This, in turn, changes the magnitude of the ambient magnetic field in the equatorial plasma trough and consequently the ion gyrofrequency and EMIC growth rate. Pc 3–5 activity was recorded at Mawson in conjunction with the Pc 1 frequency shifts and in association with rapid BIMF variations. The changes in the temperature anisotropy and energy of the resonant ions in the plasma trough, which are causing the Pc 1 emission changes, are associated with the entry of dayside Pc 3–5 pulsation energy into the dayside magnetosphere.

In order to investigate the properties of Pc 3-4 geomagnetic pulsations at very low latitudes, a conjugate study at 23° geomagnetic latitude was conducted over one month in 1988. The results show that highly polarized Pc 3-4 pulsations occur mainly in the morning from 0400 to 1000 LT. This occurrence distribution appears to be a consequence of hydromagnetic wave source and/or propagation characteristics rather than ionospheric effects. Most of the observed signals have small ellipticities, and the east-west component is enhanced near local sunrise. The polarization major axes show mirror symmetry in opposite hemispheres. Calculations of the toroidal mode eigenfrequency using actual ionospheric data to fit plasma density models show that the observed signal frequencies at 23° geomagnetic latitude are similar to the eigenfrequencies at 40°–50° latitude. Events observed simultaneously between 23° and 45° latitude suggest that Pc 3-4 at the very low latitude conjugate stations may be associated with field line resonances near 45° latitude. Possible source mechanisms of these pulsations are global mode resonances or trapped fast mode waves in the plasmasphere driving forced field line oscillations at very low latitudes.

The amplification of electromagnetic ion cyclotron (EMIC) waves in the magnetosphere is studied by integrating local convective growth rates along the wave path. The integrated wave amplification is used to investigate the radial extent of wave source regions. Typical heavy ion concentrations (He+ ∼10-20%, O+ ∼1-10%) are considered in the calculation. In contrast to previous studies, the results presented indicate that the radial structure of the integrated wave amplification is controlled by the ion composition in the magnetosphere, as well as by the cold (or thermal) plasma density profile. It is found that the source region of the lowest-frequency wave branch (i.e., the O+ wave branch here) is confined to the plasmapause and inside the plasmasphere, whereas the other wave branches (i.e., the He+ and H+ wave branches here) can be amplified over most of the magnetosphere. It is suggested that the structured Pc 1-2 waves observed mainly on the ground are due to the lowest-frequency wave branch, and the unstructured Pc 1-2 waves observed both on the ground and in space result from the other wave branches.

Geomagnetic field line resonances may be identified in ground magnetometer data by comparing the difference in amplitude and phase of signals recorded at two closely spaced sites or by examining the latitudinal variation in polarization properties across a more extended array. These two methods give comparable results for values of the resonant frequency and width at low latitudes (L < 3). We have also found an upper limit for the damping factor, γ∼0.07 at L=1.8, by applying a damped simple harmonic oscillator model. The field line resonance structure observed in 5 weeks of data showed only one resonant frequency at L=1.8 but up to four harmonies concurrently at L=2.8. An early local morning decrease in eigenfrequency was usually present at L=1.8. This is attributed to dynamic heavy ion mass loading effects in the ionosphere where the plasma density increases around dawn. The observed eigenfrequencies were used to evaluate two plasma density models. Calculations using a combined IRI-90 and diffusive equilibrium (DE) model gave eigenfrequencies which are considerably smaller than the experimentally observed values at both L=1.8 and L=2.8. Furthermore, the calculated harmonic spacings at L=2.8 do not agree with the experimental values, although the diurnal trends were successfully modeled using the IRI-DE plasma description. The low-latitude plasma density model described by Bailey (1983) yields eigenfrequencies which show good agreement with the experimentally observed values at both latitudes.

Au cours des dernieres annees, la methode goniometrique permettant de trouver les directions d’arrivee a ete appliquee aux sources de sifflements de tres basse frequence. Nous avons adapte cette technique de facon a pouvoir l’utiliser dans la bandeUbf.On se sert de deux bobines croisees et l’on synthetise par des methodes electroniques, un signal equivalent a une bobine tournante. La methode est utilisee pour determiner l’azimut de la source des pulsations geomagnetiques de type pc 1 se propageant dans le guide de la region F 2 depuis les latitudes elevees jusqu’aux latitudes moyennes. Les donnees enregistrees sont numerisees par un mini ordinateur et les analyses par transformee de Fourier rapide et par correlation sont faites pour calculer les azimuts. On discute quelques aspects de la methode goniometrique, particulierement importants pour l’etude des pc 1, ainsi que les techniques d’analyse de donnees.

Information on the high latitude source of hydromagnetic emission type Pc1 geomagnetic pulsations at ionospheric heights may be obtained using time delay location direction of arrival and polarization observations. Assuming plane wave ionospheric wave-guide propagation preliminary results of the digital analysis of data recorded in south east Australasia indicate persistent source regions during the night-time hours. Elliptical wavefront analysis methods may be used to broadly estimate the shape and orientation of the source wavefrpnts. Estimation of the accuracy of the location techniques for determining the source position is considered.

The radial Alfven velocity, V(A), in the magnetosphere was investigated using magnetic field and plasma data from the ISEE-1 spacecraft. The harmonic frequency structure calculated from these data was compared with the observed resonant wave structure in the frequency range 5-100 mHz and over the region L = 3-9. It was found that the frequency of these resonances depend on the A(V), which is a function of the magnetic field strength and plasma density. The toroidal mode resonance frequency structure was modeled for the first four harmonics, with excellent agreement between the modeled and observed harmonics for a passs which does not show a plasmapause gradient. In the presence of a steep plasmapause gradient, the model was found to predict a correspondingly steep increase in the resonance frequencies at the plasmapause, by about 5 mHz for the first harmonic and by 20 mHz for the fourth harmonic. Special consideration is given to the effect of heavy ion mass loading on the modeling.

Structured Pc 1 signals propagate in the ionospheric F 2 region duct from their secondary sources at high latitudes to lower latitudes. Propagation directions to low latitude stations can be inferred from measurements of polarization parameters. The analysis of five events recorded at two low latitude stations ( L = 1.9) are presented. Direction of arrival measurements are used to investigate the spatial and temporal structure of Pc 1 sources. Results show a close relationship between the structure of events identified in the frequency-time representation and direction of arrival measurement patterns. Multiple sources are sometimes indicated.

Ces dernieres annees, grâce a l’Eim(Etude Internationale de la Magnetosphere) ont vu se manifester un regain d’interet pour les etudes de pulsations geomagnetiques a partir de plusieurs stations, etudes ayant pour objectif la comprehension des processus de generation et de propagation. Ces reseaux de stations peuvent etre entierement constitues de stations au sol, mais peuvent egalement etre une combinaison de stations au sol et en satellite, ou de deux satellites ou plus. Un aspect tres important de ces etudes est la mesure des differences de temps d’arrivee des signaux parvenant aux stations. L’auteur decrit les techniques usuelles d’analyse par intercorrelation et d’analyse interspectrale, qui sont souvent utilisees. Il considere avec attention l’adaptation de ces methodes au traitement en temps reel, ainsi que leurs limites et leur precision. Pour illustrer ces techniques, il presente les details de l’analyse de pulsations geomagnetiques de type Pc 1 (0.2–5 Hz) enregistrees au sol.

Information on the temporal movement in the source of IPDP (intervals of pulsations of diminishing period) have been obtained by applying time delay location techniques to two events recorded at three stations in Southeast Australia. It is found that IPDP events propagate from coherent finite high latitude source regions to middle and low latitudes in the ionospheric duct. A westward drift in the source location in the early evening hours is observed as the IPDP frequency increases with time. This is attributed to the energization of ~50 keV substorm associated protons as they drift azimuthally and move to lower L -values under the influence of electric field convection.

The polarization method of source location has been used on data from two low latitude stations (L = 1.9) to determine the exit region of structured Pc1 emissions from the magnetosphere into the ionosphere. Propagation directions in the ionospheric F2 duct can be inferred from measurements of polarization parameters made at the low latitude recording station. Measurements on six events indicated an average source L value of 3.2, which represented the sources being on the average 1.0 ± 0.5 Re inside the corresponding statistical plasmapause position.

Geomagnetic pulsations in the Pc3 period range (10–45 sec) were recorded simultaneously in south-east Australia using an array of four low latitude induction coil magnetometers over a longitudinal range of 17° atL=1·8 to 2·7. Geomagnetic data from March 25 to September 21, 1982 were digitized and spectral studies were carried out from Grey scale digital (GSD) dynamic spectra and contour sonagrams. Similar wave spectra were generally seen at the three stationsWM, BH andNC in the same latitude with Pc3 waves mostly being observed in the 40–45 mHz band. In addition the higher latitude station (LN) also showed lower frequency Pc4 bands (≈ 10mHz) on some days but higher frequency bands (60–80mHz) on others. Sometimes completely different wave frequencies were observed on theX andY components with the stations in the same latitude generally showing similar spectra on the corresponding components. Dynamic spectra also indicated that wave energy often turned off and on abruptly over short intervals of time implying solar wind control and Pc3 pulsation activity. A band harmonic structure was occasionally seen in wave spectra at the azimuthal stations mainly on theX component during the local afternoon with a harmonic spacing (Δf) of ≈ 10 mHz.

An array of four low latitude induction coil magnetometer stations has been used to study the spatial and temporal characteristics of Pc3 pulsations over a longitudinal range of 17° atL=1·8 to 2·7 in south-east Australia. A preliminary study of individual Pc3 wave packet structure at the azimuthal stations has established the existence of phase jumps between wave packets at low latitudes similar to those observed at synchronous orbit and at higher latitude ground stations. However there did not appear to be any obvious pattern in phase jump occurrences between stations or signal components.

Bruce J. Malina and Jerome H. Neyrey, Calling Jesus Names: The Social Value of Labels in Matthew, reviewed by Barry W. Henaut Xavier Leon-Dufour, Sharing the Eucharistic Bread: The Witness of the New Testament, reviewed by Dan Donovan Paul J. Achtemeier, The Quest/or Unity in the New Testament Church: A Study in Paul and Acts, reviewed by James M. Reese Francis J. Moloney, The Living Voice of the Gospel: The Gospels Today, reviewed by Elaine Guillemin Gerald O'Collins, Jesus Risen: An Historical, Fundamental and Systematic Examination of Christ's Resurrection, reviewed by Lewis S. Fiorelli Alice L. Laffey, An Introduction to the Old Testament: A Feminist Perspective, reviewed by Kathleen M. O'Connor Walter Brueggemann, Israel's Praise: Doxology Against Idolatry and Ideology, reviewed by Michael B. Dick Lucien Richard, Is There a 'Christian' Ethics?, reviewed by Marsha A. Hewitt Vigen Guroian, Incarnate Love: Essays in Orthodox Ethics, reviewed by Jeffrey Gros J. Gordon Harris, Biblical Perspectives On Aging,' God and the Elderly, reviewed by Richard W. Moore Gustavo Gutierrez, On Job: God-Talk and the Suffering of the Innocent, reviewed by Harold Wells Robert O'Driscoll and Lorna Reynolds, eds., The Untold Story: The Irish in Canada, reviewed by Mark G. McGowan D.C. Smith, Passive Obedience and Prophetic Protest: Social Criticism in the Scottish Church, reviewed by Brian J. Fraser R. Laurence Moore, Religious Outsiders and the Making of Americans, reviewed by Bryan Hillis Reginald Bibby, Fragmented Gods: The Poverty and Potential of Religion in Canada, reviewed by Ian M. Manson Walter Burghardt, Preaching: The Art and the Craft, reviewed by Stephen Farris James Gollnick, Dreams in the Psychology of Religon, reviewed by R. Barnes

An array of four low latitude induction coil magnetometer stations has been used to study the spatial and temporal characteristics of Pc3 pulsations over a longitudinal range of 17° at L = 1.8−2.7 in Southeast Australia. Pc3 data over a period of about 6 months have been investigated. Interstation phase variations and polarization characteristics have been investigated in detail for 10 selected individual days common to all four stations. The East-West station chain shows generally highest coherency between X (North-South) components with relatively small interstation phase differences corresponding to low azimuthal wave numbers (| m x , y | ≲ 10). Wave spectra are generally the same at the azimuthai stations ( L = 1.8) but are often different at the higher latitude station ( L = 2.7) while wave polarization ellipticities and major axis azimuth directions at all four stations are generally similar. Diurnal variations in interstation phase indicate that Pc3 waves propagate away from local noon towards the night time with left-hand polarization and North-East major axis azimuth directions in the morning and right-hand polarization and North-West azimuth directions in the afternoon. Apparent meridional propagation is always away from the equator from North to South with | m x , y | L > 3. The resonance may be associated with the plasmapause region or field line resonances resulting from coupling with a global compressional wave mode of low wave number which is capable of propagating energy from the subsolar upstream or magnetosheath regions into the magnetosphere and down to lower latitudes near the noon meridian.

Experimental investigations on the horizontal propagation of Pc 1 pulsations in directions out of the geomagnetic meridian have been carried out using data recorded over a three-year period at four widely-separated middle and low latitude stations. The results obtained show that Pc 1 signals propagate in off-meridian directions, and that horizontal propagation characteristics in the early morning hours have small directional changes.

The reading public of the Anglo-Saxon world made the Reverend C. W. Gordon a best-selling novelist. It bought over thirty million copies of the twenty-six novels he published between 1898 and 1936 under the pseudonym of Ralph Connor. Literary critics and historians have examined Connor's novels as romantic and colourful accounts of the opening of the Canadian West, as expressions of a particular school of nationalism, or as manifestations of early twentieth century reformism. I But for the minister of St. Stephen's Presbyterian Church in Winnipeg, the novels served primarily as a means of promoting an aggressive evangelical Protestantism that saw Christianity as the most powerful dynamic in the moral and social life of the young Canadian nation. Gordon's novels, by his own estimation, presented the Gospel as 'a synonym for all that is virile, straight, honourable and withal tender and gentle in true men and women' , and sought to persuade people of the practical power of Christianity. Given the remarkable reception accorded Gordon's novels, Ralph Connor's Christianity is an important window into the Protestant mind in Canada in the opening years of the twentieth century.

An array of four low latitude induction coil magnetometer stations has been used to study the spatial and temporal characteristics of Pc 3 pulsations over a longitudinal range of 17° at L = 1.8 to 2.7 in southeast Australia. A preliminary study of individual Pc 3 wave packet structure at the azimuthal stations has established the existence of phase jumps between wave packets at low latitudes, similar to those observed at synchronous orbit and at higher latitude ground stations. However, there did not appear to be any obvious pattern in phase jump occurrences between stations or signal components.

A patient with partial trisomy 9 (47,XX,+9pter----q22.1) had bilateral cleft lip and cleft palate, enophthalmos, severe micrognathia, small, apparently low-set ears, and dislocatable knees. The phenotypic findings are compared with those of other documented cases of total trisomy 9.

Detailed study of two Pc 1 hydromagnetic emission events observed at Great Whale River, Quebec; Boulder, Colorado; and College, Alaska, indicates that emission energy propagated westward in an ionospheric duct from an extended source region east of Great Whale River with duct velocities ranging from 500 to 2500 km s−1. Sources located using both triangulation direction of arrival and polarization techniques were found to be generally consistent. Autocorrelation measurements of fine structure element spacing within the events show that dispersion increased with longitudinal distance from the source.

Ion cyclotron waves generated in the magnetosphere by the ion cyclotron instability of protons are thought to be the origin of Pc 1-2 geomagnetic pulsations. Propagation characteristics of these waves have been measured using ATS-6 synchronous satellite magnetometer wave data. Of particular interest are the wave spectra, polarization properties, and wave diagnostics; all are characteristic of propagation in a cool ambient magnetospheric plasma containing He(+) and O(+) heavy ions.

Analysis of occurrence of hydromagnetic emissions recorded during 1967 at two Australian stations, Newcastle and Hobart, has shown that about two thirds of the activity recorded at a given station, including most large amplitude events, is recorded simultaneously at the other station. Most events having a mid-frequency above 2-0 Hz occurred simultaneously at the two stations. Propagation of these events in the ionospheric hydromagnetic duct is shown to have a significant influence on the middle latitude occurrence statistics.

Pc1 geomagnetic micropulsation data recorded at Christchurch, New Zealand, and Newcastle, N.S.W., is examined for diurnal and stormtime variations in hydromagnetic emissions. The application of hydromagnetic wave packet dispersion theory to hydromagnetic emission propagation path latitude determination shows that: (1) emissions are generated in the 4·5 ≲ l ≲ 9·5 region of the magnetosphere; (2) there is a significant diurnal variation in propagation paths of approximately 2–3 Earth radii; (3) there is a geomagnetic storm-time depression in propagation paths of 1–2·5 Earth radii for moderately severe storms ( K p ⩾ 6), and a recovery rate of approximately 0·5 Earth radii/day. It is suggested that the diurnal variation in propagation paths may provide a simple explanation for the variation in hydromagnetic emission occurrence with latitude. The magnitude of the diurnal and storm-time variations support the idea of hydromagnetic emission generation by low energy trapped protons.

The dispersive propagation of Pcl hydromagnetic emissions in a proton-helium magnetosphere is considered. The addition of singly charged helium ions to the medium allows the propagation of hydromagnetic nose emissions. A graphical method which determines the nose emission propagation path, and the proton and helium concentrations at the top of the path, is presented. Only three of twelve nose emissions considered are consistent with the proton-helium explanation. The propagation of two or more adjacent narrow-band emissions along different tubes of force in a proton magnetosphere is considered as an alternative explanation. It is also shown that propagation path L values of normally dispersed hydromagnetic emissions may be increased by 0.1–0.5 Earth radii by helium concentrations of 3–10 per cent.

This paper presents a theoretical investigation of the ducting of Pc1 hydromagnetic waves in an ionospheric layer situated above the F2 region. Theoretical calculations show that this upper ionospheric duct may also sustain horizontal propagation of Pc1 pulsations over appreciable distances. It is found that there is a low-frequency cutoff as in the case of the F2 layer waveguide. The group velocity of waves in the upper ionospheric duct is considerably greater, and dispersion is more pronounced compared to the ducted propagation in the F2 region.

Magnetic pulsations are ultra-low frequcncy (ULF) oscillations in the geomagnetic field with periods of the order of 1?1000s. These pulsations are manifestations of hydromagnetic waves gencrated in the magnetosphere by a variety ofphysical processes and instabilities. Pc3?4 waves fall in the period range 10?150 s and appear to be produced by resonant oscillations of the earth's magnetic field lines, generally driven by the solar wind as it flows around the magnetosphere. Figure 1 shows a schematic representation of these iriteraclion regions.

Disseminated arteritis with extensive involvement of the aorta, as well as involvement of the arch vessels, coronary arteries, and pulmonary arteries, but not of the arteries within the liver, spleen, kidneys, or other organs, is unusual in a newborn. The presence of both acute and chronic inflammation with fibrosis, as well as calcification and focal ossification in the aorta, would suggest that the process had been present for some time before birth. This lesion should be described rather than designated by an eponym or included with such entities as Takayasu's disease. An additional finding of interest was widespread calcification in Bowman's capsules of numerous glomeruli.

In the past slow-speed frequency-modulated analogue tape recording techniques have provided the most convenient method for recording ground-based Pc1 pulsation data on a continuous basis. With events occurring often only a few hours in a week, and a Nyquist frequency of 4–5 Hz, direct digital recording is not practical because of the bulk of data accumulated. However, with the recent availability of reasonably priced microcomputers and advanced signal processing techniques it is now possible to preprocess digital data in the field and store only events of interest. A two-component induction coil magnetometer incorporating a Z80 based 64K RAM microcomputer-floppy disk preprocessing system is described. It is capable of recording Pel signals in the 0.2–4 Hz band at middle-to-low latitudes with a minimum detectable signal level of 3 pT. The reliability and limitations of the preprocessing techniques utilizing FFT autospectral analysis to recognize Pel signals are discussed.

The Conference was called to bring together investigators of magnetospheric plasma waves having frequencies from VLF whistlers and emissions down through ELF and ULF to Pc5 long period pulsations. The emphasis was on the physics and techniques underlying the entire frequency range. Topics included wave electron interactions and electron precipitation, ray tracing and other methods to track down sources of VLF and ULF waves, VLF-ULF relationships, heavy ion effects in ULF propagation, and long period ULF waves.

Ion cyclotron waves (hereafter ICW's) generated in the magnetosphere by the ion cyclotron instability of 10–100 keV protons are now known to be the origin of short-period (0.1–5 Hz) electromagnetic field oscillations observed by synchronous spacecraft and on the earth's surface. Observations of the various wave characteristics, including spectral and polarization properties that lead to the identification of generation and propagation mechanisms and regions in the magnetosphere are described with reference to ATS-6, GEOS and ground-based wave data and interpreted using cold plasma propagation theory. The presence of heavy ions (O+, He+) dramatically modifies ICW magnetospheric propagation characteristics giving rise to spectral slots and polarization reversals. These properties may be used in plasma diagnostics. Finally satellite-ground correlations and techniques for determining the magnetospheric source position of ICW's not seen at synchronous orbit but observed on the ground as structured Pc1 pulsations are considered.

The mechanism of emplacement of ultramafic intrusions has been a controversial subject for many years. This thesis summarizes evidence favoring the intrusion of ultramafic rocks as magmas. Experiments were conducted to study the effect on the melting behavior or ultramafic rocks of carbon dioxide, sodium, sulphur and water at temperatures up to 925°C. and pressures up to 2125 atmospheres. No melts were produced but it is felt that the evidence presented justifies further work on the problem.

The existence of cold or cool heavy ions in the magnetospheric plasma of the earth has been known since early GEOS-I ion composition experiment results in 1977 (Geiss et al. 1978). Helium (He+) and oxygen (O+) relative concentrations of up to 50% of the total ion concentration were found. The reliability of these particle concentrations are difficult to estimate. Unresolved wave modulations, giving rise to plasma flows and other problems including spacecraft charging. make concentration measurements difficult. Mauk (1984) has recently shown, by computer simulation, that particle concentrations measured in association with linear interaction between a wave and He+ ions may be artificially inflated by an order of magnitude. An extremely simple and sensitive measure of heavy ion (He+, O+) relative ion concentrations can be made using the bounding surfaces associated with the propagation of ion cyclotron waves in a multicomponent cold plasma. Obviously, measurements can be made only in thc prcsence of ion cyclotron wave energy which occurs in the Pcl?2 geomagnctic pulsation frequency range (0.1?5 Hz).

The relation between Pi 1-2 pulsations on the ground and substorm-associated magnetic field variations in space has been studied using data obtained on the ground at low-latitude conjugate stations (L = 1.3-2.1) and in the near-Earth magnetotail by the AMPTE CCE spacecraft. The ground-based data were acquired in a campaign period from July 20 to September 16, of 1986, during which the apogee of CCE (8.8 R{sub E}) was located between 2330 and 0230 hours magnetic local time. Of 16 clear magnetic field dipolarizations observed at CCE, all had a corresponding Pi 2 pulsation on the ground, with a time lag of +1 to {minus}7 min. For most (13) of these cases, the time lag was equal to or shorter than 2 min. However, the authors also found Pi 2 pulsations that do not accompany a dipolarization at CCE. These results are consistent with previous observations, which showed that Pi 2 pulsations are a global indicator of the expansion phase onset of a substorm, whereas dipolarizations occur in a limited region in the near-Earth magnetotail. One of the 16 events, which occurred on August 28, 1986, is studied in detail because a 13-s Pi 1 pulsation was observed on themore » ground in addition to an ordinary Pi 2 pulsation. For this event, CCE also observed a {approximately} 13-s oscillation at {approximately} 8.1 R{sub E} in the midplane of the magnetorail near midnight (Takahashi et a., 1987). They suggest that field line resonance driven by a quasi-monochromatic oscillation in the near-Earth tail is the cause of the Pi 1 pulsation observed on the ground. The commonly observed Pi 2 pulsations could be attributed to other wave excitation mechanisms including transient response of the magnetospheric cavity to a substorm-associated impulse.« less

In order to extend both theoretical and experimental investigations of low-latitude Pc 3 magnetic pulsations, we conducted conjugate magnetic observations at Asahikawa (ASH; λ = 142.2°, Φ = 43.93°, L = 1.55) and Onagawa (ONW; 141.48°, 38.43°, 1.30) in Japan and Birdsville (BSV; 139.3°, −25.83°, 1.55), i.e., the conjugate point of ASH, Dalby (DAL; 151.2°, −27.18°, 1.56) and St. Kilda (SKD; 138.5°, −34.7°, 2.11) in Australia, during the period from July 20 to September 16, 1986. From the analysis of these conjugate-area data, occurrence and polarization characteristics of low-latitude Pc 3 pulsations can be summarized as follows: (1) The average amplitude at SKD (L = 2.1) is about twice that at BSV (1.55). (2) The H component amplitude at BSV in the winter hemisphere is larger than that at ASH in the summer hemisphere. (3) The polarizations at all stations switch statistically from left-handed in the morning to right-handed in the afternoon, where polarization senses are defined with reference to the direction of the main geomagnetic field. (4) However, the switch from L-H to R-H polarization at the conjugate stations (L = 1.55) does not always occur near local noon, but sometimes near 0500 and 1700 LT. (5) The abrupt changes of major axis orientations of Pc 3 polarization ellipses appear to coincide with the ionospheric conductivity enhancement and depression, respectively, associated with local sunrise and sunset. These observational facts suggest that a standing field line resonance in the Pc 3 frequency range is situated at L >2.1, and that at lower latitudes (L ≲ 1.5) Pc 3 magnetic pulsations could arise predominantly from compressional mode waves propagating transverse to the Earth's magnetic field through the low-latitude ionosphere.

The magnetospheric generation and propagation characteristics of ion cyclotron waves associated with a Pc 1 emission observed by a network of four middle and low-latitude ground stations are determined using ground source location techniques and ISEE 1 plasma data. The source region at L = 4.7 {plus minus} 0.7 is determined from propagation in the F{sub 2} region ionospheric duct using wave polarization characteristics at ground stations. This source is just inside the steep plasmapause seen by ISEE 1 at L = 4.9 {plus minus} 0.1. The ion cyclotron wave packet interhemispheric bounce period measured from the ground spectra increases with time from 140 to 155 s during the event but is in agreement with dispersion calculations undertaken using ISEE 1 electron density and cool to cold ion composition data in a H{sup +} plasma with 8-10% He{sup +} and

Two types of Pc 1-2 wave events have been identified in ATS 6 flux gate magnetometer data recorded approximately 12 deg off the geomagnetic equator. Left-hand polarized waves observed in the afternoon are typical of IPDP ground events. Highly elliptical and linearly polarized waves occur around local noon. Spectra often show slots near the equatorial helium and oxygen cyclotron frequencies. The linear polarization may be interpreted in terms of propagation at a large wave normal angle or a crossover frequency that is a consequence of propagation in a multicomponent plasma. The spectral slots may be associated with either heavy ion cyclotron resonanace or propagation effects.