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Oxidative stress, caused by free radicals within the body, has been associated with the process of aging and many human diseases. Because free radicals, in particular superoxide, are difficult to measure, an alternative indirect method for measuring oxidative stress levels has been used successfully in Escherichia coli and yeast. This method is based on a proposed connection between elevated superoxide levels and release of iron from solvent-exposed [4Fe-4S] enzyme clusters that eventually leads to an increase in hydroxyl radical production. In past studies using bacteria and yeast, a positive correlation was found between superoxide production or oxidative stress due to superoxide within the organism and electron paramagnetic resonance (EPR) detectable "free" iron levels. In the current study, we have developed a reliable and efficient method for measuring "free" iron levels in Caenorhabditis elegans using low-temperature Fe(III) EPR at g=4.3. This method uses synchronized worm cultures grown on plates that are homogenized and treated with desferrioxamine, an Fe(III) chelator, prior to packing the EPR tube. Homogenization was found not to alter "free" iron levels, whereas desferrioxamine treatment significantly raised these levels, indicating the presence of both Fe(II) and Fe(III) in the "free" iron pool. The correlation between free radical levels and the observed "free" iron levels was examined by using heat stress and paraquat treatment. The intensity of the Fe(III) EPR signal, and thus the concentration of the "free" iron pool, varied with the treatments that altered radical levels without changing the total iron levels. This study provides the groundwork needed to uncover the correlation among oxidative stress, "free" iron levels, and longevity in C. elegans.

The outer radiation belt injection, transport, acceleration and loss satellite (ORBITALS) is a small satellite mission proposed as a Canadian contribution to the satellite infrastructure for the International Living With a Star (ILWS) program. The ORBITALS will monitor the energetic electron and ion populations in the inner magnetosphere across a wide range of energies (keV to tens of MeV) as well as the dynamic electric and magnetic fields, waves and cold plasma environment which govern the injection, transport, acceleration and loss of these energetic and space weather critical particle populations. ORBITALS will be launched around 2010–2012 into a low-inclination GTO-like orbit which maximizes the long-lasting apogee-pass conjunctions with both the ground-based instruments of the Canadian Geospace Monitoring (CGSM) array as well as with the GOES East and West and geosynchronous communications satellites in the North American sector. Specifically, the ORBITALS will make the measurements necessary to gain fundamental new understanding of the relative importance of different physical acceleration and loss processes which are hypothesised to shape the energetic particle populations in the inner magnetosphere. The ORBITALS will also provide the raw radiation measurements at MEO altitudes necessary for the development of the next-generation of radiation belt specification models, and on-board experiments will also monitor the dose, single-event upset, and deep-dielectric charging responses of electronic components on-orbit. In this paper we outline the scientific objectives of the ORBITALS mission, discuss how the ORBITALS will lead to solutions to outstanding questions in inner magnetospheric science, and examine how the ORBITALS will complement other proposed inner magnetosphere missions in the ILWS era.

It has generally been assumed in the past that the plasmapause is a preferred region for the generation and propagation of electromagnetic ion cyclotron (EMIC) waves in the Earth's magnetosphere. One assumption invoked the overlap of the expanding cold plasmapause with the inner edge of the hot ring current during storm recovery to provide favourable conditions for EMIC instability. The plasmapause was also expected to provide a convenient gradient for guiding the waves from equatorial sources to higher latitudes. The paper commences from a historic perspective and reviews the development of the ideas from the 1960s that relate the source of EMIC waves to the plasmapause. CRRES spacecraft observations of EMIC wave events over L = 3.5 –8 and associated plasmapause locations indicate that the plasmapause is a region of wave generation and propagation, with significant wave power seen in the plasmatrough, but is not necessarily the preferred region. Other results show that wave occurrence predominates in the afternoon and increases with radial distance and a He+ slot is seen in the data. These agree with earlier AMPTE-CCE results from Anderson et al. (J. Geophys. Res. 97 (1992) 3075, 3089). New results from CRRES show all wave polarisations (left-hand, linear, and right-hand) are seen within 8° of the equator whereas linear predominates over 20–30° latitude. Waves are observed in background plasma densities of 4– 300 cm −3 . Wave frequencies above the He+ cyclotron frequency are concentrated outside the plasmapause in lower density regions of 2– 30 cm −3 .

Significant similarities have been identified in the dynamic power spectra of induction magnetometer data recorded at the conjugate cusp stations of Davis, Antarctica (mlat −74.3, mlong 101.5) and Longyearbyen, Svalbard (mlat 75.0, mlong 114.5). A 60 day period in 1993 (January–February) has been studied to characterise two common features, 1) Broadband Pc5 bursts which predominantly occur 2–4 hours before and after local magnetic noon, and which exhibit polarisations suggestive of a Kelvin-Helmholtz-like source mechanism, and 2) A resonance structure which has an arch-shaped local time dependence. Interhemisphere phase measurements indicate odd-mode toroidal standing-waves after field line resonance and azimuthal propagation effects are taken into account. Phase studies such as this may be used to study conjugacy at high latitudes and identify the location of the open and closed field line boundary, an important diagnostic parameter in space weather studies.

The propagation and attenuation of isotropic fast mode waves parallel to the Earth's surface in the ionospheric F2 region waveguide have been observed as Pc 1–2 (0.1–5 Hz) geomagnetic pulsations by a network of three closely spaced stations at Davis, Antarctica. The wave properties observed are consistent with fast mode wave propagation with phase velocities of 300–800 km s−1, close to the Alfven velocity at these heights. Attenuation across the network is in the range 10–95 dB/1000 km with a 1 e folding distance of 310±220 km and are higher than attenuation at low and middle latitudes.

Late in the year 2000 Australia will launch its first satellite in thirty years. FedSat is a research microsatellite with a complement four scientific and engineering payloads. It will be placed in a near-circular sun synchronous 10:30 LT polar orbit at an inclination of 98.7° and altitude 800 km. The primary scientific experiment is a fluxgate magnetometer which will observe field aligned current structures above the auroral zones and other current systems and ultra-low frequency (ULF) plasma waves in the upper ionosphere. A major objective is to study the ionospheric signatures of regular and impulsive ULF waves propagating from the magnetosphere along geomagnetic field lines. An on-board GPS receiver will monitor the vertical and oblique total electron content (TEC) up to the GPS satellites at an altitude of 20,000 km. The communications experiment will test systems of use in future LEO constellations and satellite-ground communications. Research in satellite systems will concentrate on the use of GPS for real time tracking of small satellites while a high performance computer will test the operation of reprogrammable hardware. This paper concentrates on the research to be undertaken using the fluxgate magnetometer and describes the instrumentation.

Considerable attention has recently been focused on the interaction between downgoing hydromagnetic waves, manifested as ULF pulsations on ground magnetometer records, and the ionospheric plasma. Models of the interaction involve parameters which require experimental evaluation. We consider two aspects. First, new measurements of standing oscillations of low latitude geomagnetic field lines permit the calculation of the ionospheric scale size of the pulsation signal and the damping factor. The role and diurnal variation of ionospheric O+ may also be monitored. Second, we discuss observations of correlated ULF oscillations measured in the F region using HF Doppler sounders, and on the ground with magnetometers, during a six month campaign. Statistical data and case studies illustrate that a simple phase relationship exists between certain classes of magnetic and ionospheric oscillations. These results raise new questions on the modelling of hydromagnetic waves in the ionosphere.

The characteristics of 1–20 mHz (Pc5) geomagnetic pulsations recorded during the daytime on the ground at cusp and boundary layer latitudes have been examined. On quiet and moderately disturbed days the major spectral contributions are due to three different mechanisms. Sustained oscillations whose properties are consistent with the Kelvin-Helmholtz instability at the low latitude boundary layer are the dominant mechanism at −70 to −75 geomagnetic latitude. Transient irregular pulsations are frequently seen at single stations at the foot of polar cap and boundary layer field lines. Occasionally similar transients occur essentially simultaneously at widely spaced stations accompanied by absorption spikes on riometer records. The latter signals are most likely due to solar wind pressure pulses on the magnetopause. At cusp latitudes the major spectral contribution arises from sustained irregular pulsations centred on magnetic noon. Although their occurrence is related to the proximity of the cusp's particle signature, it may be more appropriate to discuss these signals in terms of fluctuations in boundary layer or mantle currents.

Geomagnetic pulsations in the 0.1–2.5 Hz (Pc1–2) range recorded over 12 quiet summer days at six Antarctic stations between −62.3 and −80.6° invariant latitude were examined in order to map the spatial and temporal distribution of spectral characteristics. Ionospheric particle signatures associated with the magnetospheric cusp and boundary layer were deduced for three of these days using ground riometer, magnetometer and ionosonde measurements, and in-situ ionospheric particle data. Comparison with the magnetic pulsation data shows that specific Pc1–2 emissions are associated with these regions. Within the cusp, intense unstructured ULF noise in the 0.15−0.4 Hz range is observed. Less intense waves of this type are seen near the cusp location on mantle and plasma sheet boundary layer flux tubes. These emissions are quite distinct from the discrete, structured and narrowband emissions seen equatorward of the cusp. Whereas past discussions of cusp and cleft identification have usually focused on optical or satellite data, we conclude that ground-based observations of Pc1–2 pulsations can provide a more convenient, although less precise, monitor of high latitude features.

Three months of ground-based recordings of high latitude dayside Pc1 magnetic variations at auroral oval stations Syowa (MLAT = 67°) and Mawson (MLAT = 70°) are compared. Dynamic spectra reveal that banded unstructured Pc1 emissions (0.2–0.4 Hz) may be separated into pre-noon and post-noon activity. Although the pre-noon activity is common at Mawson, its observation at Syowa is associated with low altitude cleft-like ions being present at lower than normal latitudes, i.e. 75° MLAT. These ions are determined from DMSP satellite observations. The Pc1 emissions at both stations are interpreted as arising from ion cyclotron waves generated in the equatorial plasmatrough region. We regard the dayside cleft as the free energy source of the pre-noon Pc1 activity by supplying the equatorial magnetosphere with ions. It is believed that the ion cyclotron waves enter the ionosphere within the auroral oval, poleward of Mawson and Syowa and fast Alfven mode waves, which then arise, propagate to the stations in the F2-region ionospheric waveguide.

Physically realistic models of ULF wave generation and propagation must embody amplitude, spectrum and phase characteristics. Although observational programs often focus on the spectral properties of ULF signals, the characterization of their phase properties still remains unclear. Existing analytical procedures often make unrealistic assumptions about the spectral purity and stability of the waveform. This paper describes two techniques which may be used to evaluate the spectral and temporal evolution of phase properties in ULF signals. The procedures were tested on synthetic Pc3 pulsation-like signals before application to real multi-station low-latitude ground data. Phase analysis like this introduces a new dimension to the interpretation and modelling of ULF wave processes. For instance, the identification of harmonic and packet structures is greatly facilitated. We find that much of the apparent packet structure and phase skips in amplitude-time records is due to wave interference. However, real phase skips have been observed in multi-station ground data, and need not occur simultaneously or at the same location in both Ḣ and Ḋ components. Examination of multi-station phase-time properties allows group structure, spatial coherency, and group velocities to be inferred. In one example we infer group propagation in a south-easterly direction at 8–17 km s−1.

The influence of a cold ion parallel beam on electromagnetic waves, which have frequencies near an ion gyrofrequency, is investigated by solving the linear dispersion relation. This cold ion parallel beam may occur during the plasmaspheric refilling process in the magnetosphere. In the ion gyrofrequency range, the presence of a cold parallel ion beam leads to a new drift resonant mode, which may couple with the ion cyclotron mode and modify the topology of the wave dispersion relation. For wave generation, an anisotropic instability fed by the energetic and anisotropic protons in the ring-current is considered. For the k∥ > 0 case (k∥ is a wave number along the direction of background magnetic field), the two modes do not couple and the drift resonant mode is damped, while the ion cyclotron mode grows, due to the presence of the energetic and anisotropic protons. For the k∥ k ∥ ≈− Ω i /V ∥ . The energetic ions damp the higher frequency mode, and destabilize the lower frequency mode. As a result of the ion beam, the growth rate of the anisotropie instability may decrease (k∥ > 0, the ion cyclotron mode) or increase (k∥ V ∥ $ (0.1−1.0) × 10 2 km s −1 . In addition, a right-hand polarized nonresonant instability, caused by the ion beam, occurs at k ∥ 0 .

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.

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.

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.

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.

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.

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.