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In this article, we study the influence of the drying kinetics of a droplet on the morphological characteristics of the particles produced, in order to model the aerodynamic properties of the aerosols thus formed. We present the development of a new device allowing to analyze in detail the evaporation of droplets, from their production to the formation of a dry particle, including the nucleation of the first crystals. This experiment makes it possible to study the evaporation of the drops with a temporal resolution lower than a microsecond, and thus to detect very precisely, by image analysis, the start of crystallization. We present a first study carried out on an inorganic salt and which shows, depending on the drying conditions, a wide variety of particle morphologies., This article deals with the study of the relationship between factors governing droplet drying and resultant particle morphologies, with a specific interest in the aerodynamic properties of dried particles. This work describes a new Falling Droplet Column (FDC), which offers the capability to analyze in detail the entire evaporative lifetime of individual droplets, from generation to dry particle formation, with capability for sub-microsecond temporal resolution and subsequent offline analysis of dried particles by SEM. A comparison of evaporative profiles and resulting morphologies produced in a range of conditions for different inorganic salts is presented. We will explore the specific crystallization events through detailed imaging of aerosol droplets.

A fixed-wing Unmanned Aerial Vehicle (UAV)-based flying laboratory is currently developed in the Aerospace Engineering Program, Institut Teknologi Bandung (ITB). This laboratory will be used as the part of the teaching-learning process, especially in the flight mechanics subjects. The development process itself has reached the second phase, when the mathematical model of the flying laboratory is developed. This paper specifically discusses about the development of thrust model of a small UAV, especially Sky Surfer 1400X8, by using wind tunnel test. Wind tunnel test is conducted in a closed loop wind tunnel with 40 cm × 40 cm rectangular test section and length of 1 m, while the measurement is conducted using motor test bench developed in-house. From the test, thrust and torque data from the UAV propulsion system can be obtained, including its power and propulsion efficiency data. The results of the test show that the thrust is slightly decreasing because of the increase of airspeed, while the value of the torque is relatively constant. The maximum propulsion efficiency happens in the region of approximately 75% throttle level, while the maximum thrust is measured at the airspeed of 0 to 5 m/s and 100% throttle with the value of 5.5 N.

The contribution of this paper relies in the development of numerical algorithms for the mathematical treatment of specular reflection on borders when dealing with the numerical solution of radiative transfer problems. The radiative transfer equation being integro-differential, the discrete ordinates method allows to write down a set of semi-discrete equations in which weights are to be calculated. The calculation of these weights is well known to be based on either a quadrature or on angular discretization, making the use of such method straightforward for the state equation. Also, the diffuse contribution of reflection on borders is usually well taken into account. However, the calculation of accurate partition ratio coefficients is much more tricky for the specular condition applied on arbitrary geometrical borders. This paper presents algorithms that calculate analytically partition ratio coefficients needed in numerical treatments. The developed algorithms, combined with a decentered finite element scheme, are validated with the help of comparisons with analytical solutions before being applied on complex geometries.

The 2D radiative transfer equation coupled with specular reflection boundary conditions is solved using finite element schemes. Both Discontinuous Galerkin and Streamline-Upwind Petrov–Galerkin variational formulations are fully developed. These two schemes are validated step-by-step for all involved operators (transport, scattering, reflection) using analytical formulations. Numerical comparisons of the two schemes, in terms of convergence rate, reveal that the quadratic SUPG scheme proves efficient for solving such problems. This comparison constitutes the main issue of the paper. Moreover, the solution process is accelerated using block SOR-type iterative methods, for which the determination of the optimal parameter is found in a very cheap way.

Diffuse optical tomography problems rely on the solution of an optimization problem for which the dimension of the parameter space is usually large. Thus, gradient-type optimizers are likely to be used, such as the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, along with the adjoint-state method to compute the cost function gradient. Usually, theL2-inner product is chosen within the extraction procedure (i.e., in the definition of the relationship between the cost function gradient and the directional derivative of the cost function) while alternative inner products that act as regularization can be used. This paper presents some results based on space-dependent Sobolev inner products and shows that this method acts as an efficient low-pass filter on the cost function gradient. Numerical results indicate that the use of Sobolev gradients can be particularly attractive in the context of inverse problems, particularly because of the simplicity of this regularization, since a single additional diffusion equation is to be solved, and also because the quality of the solution is smoothly varying with respect to the regularization parameter.

This paper presents the solution of coupled radiative transfer equation with heat conduction equation in complex three-dimensional geometries. Due to very different time scales for both physics, the radiative problem is considered steady-state but solved at each time iteration of the transient conduction problem. The discrete ordinate method along with the decentered streamline-upwind Petrov-Galerkin method is developed. Since specular reflection is considered on borders, a very accurate algorithm has been developed for calculation of partition ratio coefficients of incident solid angles to the several reflected solid angles. The developed algorithms are tested on a paraboloid-shaped geometry used for example on concentrated solar power technologies.

Quantitative analysis of organonitrate explosive standards was performed by gas chromatography (GC) with dual electron capture detection (ECD2) and electron-impact ionization quadrupole mass spectrometry (EI-MS) in selected ion monitoring (SIM) detection mode. A comparison of method conditions and performance parameters, including minimum detectable limit (MDL) by compound, is presented in this technical note. The GC‐ECD2 method shows an improved 30‐250X sensitivity to dinitroaromatics, trinitroaromatics and RDX, in clean noise-limited backgrounds, and the GC‐MS method reveals a sensitivity increase of 2‐10X to high volatility mononitroaromatics, the ability to detect target analytes in complex matrices, and identify unknown compounds by mass-to-charge determination.

It has been well documented that interleukin (IL)-6 plays an essential role in periodontal disease (1). Our recent study on periodontal expression of genes known to be involved in periodontal disease showed a trend of increase in IL-6 mRNA expression in periodontal tissue across patients with neither periodontal disease nor diabetes, patients with periodontal disease alone, and patients with both diseases (p=0.02) (2). No trend of increase across the three groups was found for IL-1β, TNFα, and MMP-8, while a marginal trend of increase was observed for MMP-1 (p=0.05). Given that periodontal disease in diabetic patients is more severe than that in nondiabetic patients, these findings suggest that IL-6 may contribute to the progression of periodontal disease. Besides this report, previous studies have also provided evidence supporting that IL-6 is an important cytokine involved in the pathogenesis of periodontal disease. Interleukin-6 is abundant in the inflammatory lesions in periodontal tissues and activates fibroblasts in the presence of soluble IL-6 receptor (3). Interleukin-6 is a potent stimulator for MMP production (1). In addition to periodontal disease, it has been well established that IL-6, along with other pro-inflammatory cytokines (such as TNF-aand IL-1b), is involved in the production of the chronic and low-grade inflammation that contributes to other diabetic complications such as cardiovascular diseases (4–6). It has been proposed that IL-6 released from diseased periodontal tissue enters the blood circulation and stimulates both immune and nonimmune-related cells by activating the Janus kinase (JAK)/signal transducers and activator of transcription (STAT) and the Src homology 2-containing tyrosine phosphatase (SHP-2)/ERK/MAPK pathways and upregulating gene expression involved in inflammation (5). Although we have demonstrated a trend of increase in periodontal IL-6 expression at the mRNA level across patients with neither periodontal disease nor diabetes, patients with periodontal disease alone and patients with both diseases (2), the periodontal expression of IL-6 at the protein level in these patients has not been investigated. While an increase in mRNA expression level of a gene is frequently associated with an increase in its protein level, the extent of protein expression can be different from that of mRNA expression due to the translational regulation by the same stimulus. For example, we showed previously that the stimulation of CD14 expression at the mRNA and protein levels in U937 histiocytes by lipopolysaccharide (LPS) and high glucose was 15-fold and 45-fold as compared to those by LPS and normal glucose, respectively (7). Thus, it is important to determine the IL-6 protein level in periodontal tissue to fully elucidate the impact of periodontal disease and diabetes on IL-6 expression. In this study, we recruited 35 patients with or without periodontal disease and diabetes and collected periodontal tissue specimens at the time of necessary surgical intervention and analyzed periodontal IL-6 protein expression levels using immunohistochemistry. Quantitative data showed that periodontal IL-6 expression at the protein level is significantly increased across patients with neither periodontal disease nor diabetes, patients with periodontal disease alone, and patients with both diseases.

A campaign to measure the amount of trace explosive residues in an operational military environment was conducted on May 27-31, 2007, at the National Training Center at Fort Irwin, CA, USA. The objectives of this campaign were to develop the methods needed to collect and analyze samples from tactical military settings, to use the data obtained to determine what the trace explosive signatures suggest about the potential capabilities of chemical-based means to detect IEDs, and, finally, to present a framework whereby a sound understanding of the signature science can be used to guide development of new sensing technologies and sensor concepts of operation. Through our use of combined background and threat signature data, we have performed statistical analyses to estimate upper limits of notional sensor performance that is limited only by the spatial correlation of the signature chemicals to the threats of interest.

The rapidly evolving changes in working patterns, career structure and the regulation of training of doctors have provided an ideal opportunity for proposals to improve the programme for the training of neurosurgeons. The Education and Training Committee of the Society of British Neurological Surgeons (D.G. Hardy, A. J. W. Steers, N. T. Gurusinghe, P. M. Foy, P. van Hille, R. A. Cowie, H. A. Crockard, O. Sparrow and S. Burn) has, in recent months, worked closely with the Specialist Advisory Committee (SAC) in neurosurgery, Department of Health (Modernizing Medical Careers Group, H. A. Crockard, A. Havers, T. Hobbs) and colleagues from the major neuroscience specialties to develop a new programme based on a 'Common Stem ' approach. This article describes the principles of the programme. The proposals have received approval by the Council of the SBNS, the Presidents of the four Surgical Royal Colleges and the Senate of Surgery.

Observations of Electric Field Distributions in the Ionospheric Plasma - A Unique Strategy (OEDIPUS C) was a tethered mother-son experiment that was launched northward from the Poker Flat rocket range at 0638 UT on November 7, 1995, across a sequence of auroral structures. During the flight's upleg the magnetically aligned tether was deployed to a separation of ∼1.2 km and then cut at both ends. The forward payload contained a 50-kHz to 8-MHz stepped-frequency transmitter. Receivers were carried on both forward and aft payloads. The transmitter swept through the frequency range every 0.5 s. During each of the 3-ms steps the transmitter emitted only for the first 0.3 ms. The scientific complement also included multiangular electrostatic analyzers on both payloads that were sensitive to fluxes of electrons with energies from 20 eV to 20 keV. The durations of sampling and frequency steps were matched. During the flight the electron gyrofrequency was approximately twice the plasma frequency. When the transmitter swept through the local gyrofrequency, the particle detectors on both payloads detected sounder-accelerated electrons (SAEs) independent of the energy steps being sampled. In addition, SAEs were detected at the aft payload out to separations of several hundred meters for wave emissions at harmonics of the electron gyrofrequency as well as in the upper hybrid and whistler bands. As the vehicle separation increased, significant time differences developed between the wave-emission pulses and the onsets/durations of SAE detections. The data indicate that electrons were heated through strong wave-particle interactions. However, a simple resonant-interaction explanation appears inadequate. We outline requirements for any models purporting to explain OEDIPUS C measurements.

We report on modulations of electron fluxes at megahertz frequencies measured by the Shuttle Potential and Return Electron Experiment (SPREE) during fast pulsed electron gun (FPEG) beam experiments conducted after the tether break event of the Tethered Satellite System Reflight. Six intervals of sustained modulations were identified while FPEG emitted a 100 mA beam of 1 kev electrons. During five events the beam pitch angle α B was near 90° and the modulations were near even or odd half harmonics of the electron gyrofrequency f ce . In the sixth event with 60° > α B > 45°, electron modulations were near estimated values of the electron plasma frequency f pe and 2f pe . Whenever SPREE detected beam electrons modulated at a given frequency, secondary electrons were also modulated at the same frequency over a broad range of energies. Occasionally, some secondary electrons were modulated simultaneously at a second frequency. Multiple frequencies were related as ratios of low integers. In one case the beam electrons were simultaneously modulated at 0.8 MHz and 1.25 kHz. SPREE measurements suggest that the beam electrons propagate in cylindrical shells whose inner edge is marked by steep spatial gradients in fluxes at 1 keV [Hardy et at., 1995]. Inside the shell, electron distribution functions have positive slopes ∂f/∂v⊥ > 0 at velocities near that of the beam. Velocity space gradients act as free-energy sources to drive cavity modes that alter the instantaneous guiding centers of electrons causing SPREE to sample alternating parts of the beam cylinder's inner edge. Associated time-varying electric fields also modulated the fluxes of secondary electrons reaching SPREE. Other cavity modes may be excited through nonlinear processes [Calvert, 1982]. With α B far from 90°, electrons in the beam cylinder evolved toward bump-on-tail distributions to excite large-amplitude Langmuir modulations at f pe and its harmonics [Klimas, 1983]. Low-frequency modulations are attributed to electron interactions with ion acoustic-like waves generated as the beam moved across magnetic field lines in the ionosphere at supersonic speeds.

We have measured the transparencies of a number of candidate resist materials for 157nm, with an emphasis on determining which chemical platforms would allow resists to be used at maximum thicknesses while meeting requirements for optical density. Assuming an ideal resist optical density of 0.4, our findings show that all existing commercially available resists would need to be

During the Tethered Satellite System reflight the Spacecraft Particle Correlation Experiment detected fluxes of energetic electrons and ions that were simultaneously modulated at low frequencies during firings of both the fast pulsed electron gun (FPEG) and the electron generator assembly (EGA). The modulations have been interpreted as signatures of large-amplitude, ion acoustic-like waves excited in Cerenkov interactions between electron beams and ambient plasmas as the shuttle moved at supersonic speeds across the ionospheric magnetic field. We present examples of particle modulations observed during steady beam emissions. Measurements show that (1) most electron modulations were at frequencies of several hundred Hertz and (2) ions modulated at similar frequencies appeared at spectral energy peaks during shuttle negative charging events. Detection of modulated ion fluxes confirms the Cerenkov emission hypothesis. Observed frequency variations indicate that the EGA beam underwent more spatial spreading than the FPEG beam.

During the reflight of the tethered satellite system, the electron generator assembly (EGA) emitted steady electron beams six times with the satellite deployed between 6.2 and 16.1 km. Maximum beam energies and currents were 1.65 keV and 0.4 A, respectively. Data presented here show that: (1) emissions create local electron clouds that can charge the shuttle, (2) ionization of thruster gas by beam electrons in the sheath did not reduce the shuttle potential, (3) the EGA utilizes more than half the induced potential, and (4) ionospheric density gradients and magnetic field orientations affect the circuit's potential distribution.

We present environmental responses ob- served by the Shuttle Potential and Return Electron Experiment during 13 prolonged electron beam emis- sions from the Fast Pulsed Electron Generator (FPEG) during the TSS 1R deployment. As the tether length- ened from 0.18 to 2.5 kin, FPEG fired nine times at a nominal current of 100 mA at 1 keV. The motional potential induced across the system increased from 24 to 225 V. With a 15 fl resistor connecting the tether to shuttle ground, current was higher and the degree of negative shuttle charging lower when FPEG was off than when it was on. While most FPEG firings left the shuttle uncharged, two created significant poten- tials: one to +70 V in a nighttime, equatorial plasma depletion and one to-60 V, with the tether -15 km. the tether end and shuttle ground. The second, the Fast Pulsed Electron Generator (FPEG), emitted electrons at a fixed energy and current of 1 keV and 100 mA. This paper presents ionospheric plasma responses to extended FPEG emissions detected in the payload bay by the Shuttle Potential and Return Electron Exper- iment (SPREE). We briefly describe SPREE, FPEG and the TSS 1R circuit during FPEG operations, then present SPREE spectral data for 13 FPEG firings. Two events illustrate positive and negative shuttle charging. The last section discusses the shuttle's electrical cou

We studied 21 intervals during the TSS 1R deployment with a 15 Ω or 25 kΩ resistor connecting the tether to shuttle ground. Ion spectral peaks detected by the Shuttle Potential and Return Electron Experiment indicate that the shuttle consistently charged negatively with respect to the local plasma. With the 15 Ω shunt in the circuit, shuttle potential, Φs, decreased from −17 to −245 V as tether length, L, increased to 2.6 km. Current in the circuit depended strongly on ionospheric density. With the 25 kΩ resistor in place, Φs ≈ −300 V in the low density, nightside ionosphere with L = 5.1 km. Near local noon Φs ≈ −80 V with L = 17.2 km. The shuttle charged to ∼−600 V during two dawn terminator crossings, one with and one without thruster firings. As on TSS 1, firings of two aft vernier thrusters significantly increased |Φs|. In the case without thruster firings, simultaneous variations of Φs, tether current, and the inferred satellite potential are consistent with strong azimuthal and vertical ionospheric density gradients. These are the first known direct measurements of strong negative shuttle charging.

Experiments were conducted during the Tethered Satellite System Reflight in which a 1 keV, 100 mA electron beam was emitted from the shuttle at pitch angles near 90°. Rapid plasma responses measured by the Shuttle Potential and Return Electron Experiment (SPREE) show time-modulated electron fluxes within the beam flux tube. Megahertz modulations fall into two classes: (1) narrow-bands close to harmonics of the electron gyrofrequency fce and (2) broad-bands at interharmonic frequencies in which electrons of different energies had different modulation frequencies. When SPREE intercepted beam electrons after a single gyroturn they, too, were modulated at similar frequencies. Data suggest that beam electrons were modulated by strong plasma interactions near the emission aperture, generating time-varying electric fields that modulated other electrons near the beam cylinder. This is analogous to the electron cyclotron maser responsible for auroral kilometric radiation.

In a recent one-dimensional self-consistent hybrid code simulation of the local dipolarisation of the initially distended magnetic field in the near-earth nightside region, (Richardson and Chapman, 1994), initially isotropic ions were accelerated up to twice the Alfven speed along the direction of the magnetic field. A bistreaming ion population was generated in the weak field region at the centre of the reversing field, and monostreaming ions were found to move away from the region of dipolarisation. Moreover, a bipolar signature in the cross tail component of the field and fast magnetosonic waves propagating away from the reversal region are predicted by the simulation. We test these predictions by examining particle and magnetic field data from the Low Energy Plasma Analyser (LEPA) experiment and fluxgate magnetometer instrument onboard the Combined Release and Radiation Effects Satellite (CRRES). We examine a set of events that were found to be consistent with some of the features of the simulation results.

The Oedipus C rocket that was launched from Poker Flats, Alaska in November 1995 has detected significant local increases in the observed auroral electron precipitation flux during an auroral substorm which were not accompanied by a corresponding increase in the electric potential of the auroral electron acceleration region. The energy of the electrons which contributed to these increases in flux were also found to extend well below the electric potential energy of these electrons at the top of the acceleration region, thereby requiring a related loss in energy inside the acceleration region. This loss in energy must therefore be attributed to a wave instability which extracts energy from the electrons which are scattered into the loss cone inside the electron acceleration region to cause the discrete aurora during a substorm.

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We report the occasional detection of negative pickup ions by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the first Tethered Satellite System (TSS 1) mission. These ions appear as arch-like structures of enhanced fluxes in energy versus time spectrograms for the SPREE electron zone looking in the plane perpendicular to the Earth's magnetic field. Maximum energies of ∼56 eV were measured when the sensor looked closest to the shuttle ram direction. Empirically, the energy of associated spectral peaks decreases as cos 2 ξ, where ξ is the angle between the sensor look direction and the projection of the shuttle's velocity onto the plane perpendicular to the magnetic field. These signatures may be found under day or night conditions and always in conjunction with positively charged pickup ions generated as a result of firings by the L5D and/or R5D vernier thrusters. We show that positive ion contamination and accelerated electrons cannot be the responsible agents. Observed spectral characteristics are most easily explained as either NO 2 - or MMH - ions created near the shuttle and accelerated by the motional electric field to energies detectable by SPREE.

This paper looks at the competitive situation between rail and road transport. The economic structure and physical characteristics of both systems are examined. It is shown that it will be extremely difficult to make the railways really competitive without very great changes to both the regulation and the physical characteristics of the railway system. Some ideas on the form that these could take are given in the final part of the paper.

TABLE OF CONTENTS ABDOMINAL CRISES III: I.S.R. Sinclair, F.R.C.S. THE BIOLOGY OF MONGOLISM: R.A. Bailey, M.B., Ch.B. RES MEDICA SOME ASPECTS OF FUNCTIONAL ORGANISATION IN THE CEREBRAL CORTEX: D.G. Hardy, B.Sc. THE APPEAL FUND CONGENITAL DISLOCATION OF THE HIP: P.J. Swarbrick, M.B., Ch.B.

The androgen receptor (AR) is a structurally conserved member of the nuclear receptor superfamily. The amino-terminal domain is required for transcriptional activation and contains a region of polyglutamine encoded by CAG trinucleotide repeats. In humans, the number of CAG repeats is polymorphic; the average number is 22 in Caucasian males. Expansion of CAG repeats in the AR has clinical implications for human disease. As androgen influences prostate cancer growth, polymorphisms in CAG repeat length may affect the clinical course of patients with prostate cancer. To test for an association between clinical parameters of human prostate cancer and CAG repeat length, we analyzed normal lymphocyte DNA from 109 patients. The CAG region of the AR was amplified by the PCR. Reaction products were then amplified using end-labeled internal primers, cut at the internal PstI site and assayed on sequencing gels using a sequence ladder as a size standard. Sequence analysis of several samples validated this method for measurement of CAG repeat number. The median age of patients was 63 yr (range, 42-83), with 104 Caucasian, 2 African American, 1 Asian, and 2 other racial origin. The median repeat length was 25 for patients with stage A, 22 for patients with stage B, 22 for patients with stage C, and 23 for patients presenting with stage D disease. A significant correlation between CAG repeat length and age at onset was observed, whereas correlations with stage, level of prostate-specific antigen at diagnosis, and time to prostate-specific antigen relapse were not significant. Shorter CAG repeat lengths may be associated with the development of prostate cancer in men at a younger age. These data suggest that CAG repeat length can affect the risk of developing prostate cancer.

Data from the Shuttle Potential and Return Electron Experiment (SPREE) flown as part of the Tethered Satellite System (TSS 1) are used to determine the detailed characteristics of beam arc distributions of pickup ions due to molecules outgassed or ejected from the shuttle. These ion distributions are only detected near the plane perpendicular to the magnetic field direction in an angular range of ±45° about the minimum angle to ram. Their flux is largest when the angle between this plane and the shuttle ram direction is smallest. Generally, ion spectra peak in the range 19 to 25 eV at the minimum angle between the perpendicular plane and the ram direction. The peak energy decreases smoothly as this angle increases. Weak fluxes are measured above the peak, to energies as high as 150 eV. Within the SPREE energy range, two-dimensional distribution functions of beam arc ions in the perpendicular plane have teardrop shapes, symmetric about the minimum angle to shuttle ram with deep minima in the centers. Variations in the peak energies of differential number fluxes agree with collisionless trajectory analysis, assuming that the ions are H2O+ and allowing for different initial velocities before charge exchange. The lowest densities for beam arc ions occur during periods of purely residual outgassing from the shuttle. Ion densities increase by a factor of 5 during waste water dumps. The highest densities occur during operation of the flash evaporator system when the pickup ion densities in daylight can exceed 105 ions cm−3, about 30% of the estimated ambient plasma density. We also present a nonlinear numerical analysis to study the stability of beam arc generated plasma waves and explain electrostatic spectra measured during previous shuttle flights.

We have surveyed measurements taken by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the satellite deployment phase of the Tethered Satellite System (TSS 1) mission. The shuttle was flying in an inverse airplane mode with its engine bells facing the ram direction to facilitate ion current collection. SPREE ion spectral measurements indicate that with no thrusters firing, the shuttle charged to, at most, a few tens of volts negative. We identified 13 intervals during which the tether was electrically connected to the shuttle by a low-impedance shunt and thruster firings occurred. In previously reported examples of neutral gas releases from charged spacecraft the magnitude of the vehicle potential decreased. Thruster firings during our events either left the TSS circuit unchanged or caused the current measured in the tether to diminish and the shuttle to become more negatively charged. In the latter case it appears that thruster gas impeded access of ambient ions to the current collecting surfaces of the shuttle. The changes in the distribution of the motionally induced potential between the tether and sheath calculated using Ohm's law are in agreement with SPREE measurements.

The electrodynamics of the inner magnetosphere near times of substorm onsets have been investigated using CRRES measurements of magnetic and electric fields, energetic electron fluxes, in conjunction with ground-based observations. Six events were studied in detail, spanning the 2100 to 0000 MLT sector and L values from 5 to 7. In each case the dawn-dusk electric field was enhanced over typical background electric fields, and significant, low-frequency pulsation activity was observed. The amplitudes of the pulsations were larger than the background electric fields. Dusk-dawn excursions of the cross-tail electric field often correlated with changes in currents and particle energies at CRRES and with ULF wave activity observed on the ground. Variations of the electric field and Poynting vectors with periods in the Pi 2 range are consistent with bouncing AlfVen waves that provide electromagnetic communication between the ionosphere and plasma sheet. Magnetic signatures of field-aligned current filaments directed away from the ionosphere, presumably associated with the substorm current wedge, were observed during three orbits. In all cases, ground signatures of substorm expansion were observed at least 5 min before the injection of electrons at CRRES. Field-aligned fluxes of counter-streaming, low-energy electrons were detected after three of the injections. We develop an empirical scenario for substorm onset. The process grows from ripples at the inner edge of the plasma sheet associated with dusk-dawn excursions of the electric field, prior to the beginning of dipolarization. Energy derived from the braking of the inward plasma convection flows into the ionosphere in the form of Poynting flux. Subsequently reflected Poynting flux plays a crucial role in the magnetosphere-ionosphere coupling. Substorms develop when significant energy (positive feedback?) flows in both directions, with the second cycle stronger than the initial. Pseudobreakups occur when energy flow in both directions is weak (negative feedback?). “Explosive-growth-phase” signatures occur after onset, early in the substorm expansion phase. Heated electrons arrive at the spacecraft while convection is earthward, during or at the end of electromagnetic energy flow away from the ionosphere.

Dosimeter data taken on the APEX satellite in a 362 by 2544 km, 70/spl deg/ inclination orbit are used to produce a high resolution dose model of the inner edge of the inner proton radiation belt. The APEX data are compared to dosimeter data taken on the DMSP and CRRES spacecraft. The comparisons show that the CRRESRAD model is reliable down to 850 km and can be extended down to 350 km with the APEX data. Solar cycle variations on the inner edge of the inner belt were found to be much less than predicted by theory.

We report on the analysis of megahertz modulation of electrons as measured by the Shuttle Potential and Return Electron Experiment (SPREE) during dc firing of the shuttle electrodynamic tether system (SETS) fast pulsed electron generator (FPEG). The SPREE and FPEG were flown aboard the space shuttle Atlantis flight STS 46 as part of the Tethered Satellite System (TSS 1) mission. The principal data reported here are from the SPREE multiangular electrostatic analyzers (ESAs) and Space Particle Correlator Experiment (SPACE). The ESAs, mounted on rotary tables, measured electrons and ions in the energy range from 10 eV to 10 keV over a solid angle of 2π sr. The SPACE is a signal processing system that analyzes the pulse stream from the SPREE ESAs to identify bunching of the electrons and ions produced by coherent wave-particle interactions (WPIs). The SPACE detects modulations in the electron fluxes in frequency range 0- to 10-MHz. This paper concerns 2- to 4-MHz modulations of the electron flux detected by the SPACE when the FPEG was firing in a dc mode at pitch angles close to 90°. During such operations, FPEG emitted a current of 100 mA at an energy of 1 keV. For these times, electrons with energies from 10 to 1850 eV were measured by the SPREE. For energies between ∼10 and 100 eV the electron flux is basically isotropic. At higher energies the flux increases for pitch angles near 90°. The electron distribution functions generally decrease monotonically with increasing energy up to 100 eV. At energies >100 eV the distributions either monotonically decrease or exhibit a peak or plateau at energies near the beam emission energy. Megahertz modulations were observed for electrons with energies from 10 to 1180 eV, on both positive and negative slopes in the distribution function and throughout the 2π sr sampled by the ESAs. The occurrence and strength of the modulations exhibit no clear dependence on the pitch angle at which the electrons are measured. However, they appear to be limited to low parallel velocities (