bluuebunny/crossref_metadata_2025 huggingface dataset:
Retention of cytoplasmic droplet by rat cauda epididymal spermatozoa after treatment with cytotoxic and xenobiotic agents
Authors: Akbarsha MA , Latha PN , Murugaian P
Published: January 2004

Spermatozoa leaving the testis contain a cytoplasmic droplet which they release during transit through the epididymis before reaching the cauda epididymidis. The cytoplasmic droplet shows P450 aromatase activity, which plays a role in synthesis of oestrogen from androgen. In the present study, 3-month-old Wistar strain male albino rats were administered with the organophosphate insecticides malathion or dichlorvos, or the phytotherapeutics andrographolide or ursolic acid. Segments of the epididymis were subjected to histopathological and ultrastructural analyses and it was found that 60-95% of the spermatozoa residing in the lumen of the cauda epididymidis retained the cytoplasmic droplet. The motility of the spermatozoa released from the cauda epididymidis was inhibited. One of the mechanisms of action of these toxicants on male reproductive function may be attributed to the retention of the cytoplasmic droplet and the resultant impairment of sperm motility.
Pulsatile GnRH secretion from primary cultures of sheep olfactory placode explants
Authors: Duittoz AH , Batailler M
Published: January 2004

The aim of this study was to investigate the development of pulsatile GnRH secretion by GnRH neurones in primary cultures of olfactory placodes from ovine embryos. Culture medium was collected every 10 min for 8 h to detect pulsatile secretion. In the first experiment, pulsatile secretion was studied in two different sets of cultures after 17 and 24 days in vitro. In the second experiment, a set of cultures was tested after 10, 17 and 24 days in vitro to investigate the development of pulsatile GnRH secretion in each individual culture. This study demonstrated that (i) primary cultures of GnRH neurones from olfactory explants secreted GnRH in a pulsatile manner and that the frequency and mean interpulse duration were similar to those reported in castrated ewes, and (ii) pulsatile secretion was not present at the beginning of the culture but was observed between 17 and 24 days in vitro, indicating the maturation of individual neurones and the development of their synchronization.
Effect of TNF-alpha on LH and IGF-I modulated chicken granulosa cell proliferation and progesterone production during follicular development
Authors: Onagbesan OM , Mast J , Goddeeris B , Decuypere E
Published: January 2004

This study demonstrates the effects of recombinant human tumour necrosis factor a (rhTNF-alpha) and conditioned medium of the HD11-transformed chicken macrophage cell line on cultured chicken granulosa cells. Effects were studied on basal, IGF-I- and LH-stimulated progesterone production and cell proliferation. Recombinant human TNF-alpha stimulated basal progesterone production in a dose-dependent manner in the granulosa cells of the largest follicle but had no effect on cells from the third largest follicle. TNF-alpha stimulated and sometimes inhibited progesterone production stimulated by IGF-I and LH alone or in combination depending on the size of the follicle and the concentration of LH or IGF-I applied. However, the inhibitory effect of TNF-alpha was significantly more pronounced in cells from the third largest follicle when high concentrations of IGF-I, LH or a combination of both were applied. TNF-alpha had no effect on basal cell proliferation in both the largest and the third largest follicles, but regulated responses to IGF-I and a combination IGF-I and LH in the cells of the third largest follicle but not those of the largest follicle. The data indicate that the normal hierarchy of follicles is maintained in the chicken ovary through the regulation of the activity of IGF-I and its interaction with LH. Conditioned medium of LPS-activated HD11 macrophages mimicked the effects of TNF-alpha and its interaction with IGF-I and LH on progesterone production and cell proliferation. The observation that the HD11-conditioned medium contained TNF-alpha indicates that TNF-alpha produced by macrophages found in chicken follicles modulates granulosa cell growth and differentiation.
Sustainable development strategies in France: institutional settings, policy style and political discourse
Authors: Szarka Joseph
Published: February 2004

The sustainable development (SD) strategies of two successive French governments, led by Prime Ministers Jospin (1997–2002) and Raffarin (from 2002), are compared and analysed in relation to three debates: (i) the influence of institutional settings and levels of continuity between international, European and national policy frameworks; (ii) compatibility between SD policy frames, national policy style and institutional capacity and (iii) relationships between traditional political discourses and SD discourse. Difficulties in achieving a good ‘fit’ are identified in each of these areas, explanations are offered and implications for future developments outlined. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.
The bright and dark sides of individual and group innovation: a Special Issue introduction
Authors: Janssen Onne , van de Vliert Evert , West Michael
Published: February 2004

This introduction essay proposes a challenging program for researchers eager to explore factors and process mechanisms contributing to the benefits and costs individuals and groups incur from pursuing innovative approaches. With respect to individual innovation, such moderating factors might be found in the characteristics of the innovative idea, the innovator, co‐workers, supervisors, the broader organizational context, and in national culture. Examples of factors that are likely to shape the beneficial and detrimental outcomes of group innovation include knowledge, skills and ability of group members, group tenure, diversity among group members, group processes (clarifying group objectives, participation, constructive management of competing perspectives), and external demands on groups. This Special Issue contains a state‐of‐the‐science paper, three articles dealing with the benefits and costs of individual innovation, and three articles addressing the bright and dark sides of group innovation. Copyright © 2004 John Wiley & Sons, Ltd.
North Atlantic teleconnection patterns of low‐frequency variability and their links with springtime precipitation in the western Mediterranean
Authors: Martín M. L. , Luna M. Y. , Morata A. , Valero F.
Published: February 2004

The relationship between springtime (March–May) precipitation in the western Mediterranean area and several North Atlantic teleconnection patterns of low‐frequency variability is analysed for the period 1948–89. Singular value decomposition analysis (SVDA) of the springtime monthly mean fields for the three paired combinations of 300 hPa geopotential height–precipitation, 300 hPa zonal wind–precipitation and 300 hPa meridional wind–precipitation has shown that their covariability is dominated by two main large‐scale atmospheric circulation patterns. In every SVD combination, the first mode relates precipitation anomalies to the east Atlantic jet pattern. Above‐normal rainfall anomalies are linked with a blocking pattern affecting Iberian weather. The second covariability mode for the three SVD As takes into account the response of the precipitation to the North Atlantic oscillation (NAO) pattern. An enhanced spring NAO pattern is related to positive (negative) precipitation anomalies over the southern (northern) western Mediterranean. Through these two modes, the North Atlantic large‐scale atmospheric dynamics explains about 50% of the total spring precipitation variability in the western Mediterranean area. A Monte Carlo approach has allowed setting the statistical significance of the modes obtained and to assess the effectiveness of the western Mediterranean precipitation response to the teleconnection patterns. Copyright © 2004 Royal Meteorological Society
Azimuthal variation of ion density and electron temperature in the Io plasma torus
Authors: Herbert Floyd , Sandel Bill R.
Published: February 2004

We analyzed about 47 hours of Voyager 1 ultraviolet spectrometer observations of the Io plasma torus in order to determine the distributions of ion and electron density and electron temperature as five‐dimensional functions of (1) radius (L), (2) System III longitude (λIII), (3) System IV longitude (λIV), (4) Jovian local solar time (ϕ⊙), and (5) azimuth relative to Io (ϕIo). We present averaged profiles of electron density (ne) and temperature (Te) as one‐dimensional functions of each of these five variables in turn. Each of these profiles is an average of the full five‐dimensional distribution over the other four variables. Our Te(L) estimate is substantially the same as that determined from in situ observations by the Voyager 1 plasma science investigation. As for the azimuthal profiles, we find that the ne(λIII) profile has a peak near λIII=180°, as expected from ground‐based observations, while the Te(λIII) profile peaks around λIII=300°. The Jovian surface magnetic field reaches its lowest magnitude on the Io footprints near the Te(λIII) maximum, suggesting that part of the torus electron heating might be associated with Birkeland currents or some other magnetosphere‐ionosphere coupling. In the Io frame, we find an apparent ne(ϕIo) maximum about 90° downstream from Io while the highest Te(ϕIo) occurs near Io, suggesting that electrons are locally heated by the Io atmosphere‐torus MHD interaction. These two Te profiles suggest that field‐aligned currents might comprise the long‐sought additional (i.e., besides fresh ion pickup) electron‐heating power source for torus emissions needed to resolve the torus “energy crisis”. In local solar time, we find that the Te(ϕ⊙) and ne(ϕ⊙) profiles peak between dusk and local midnight, with the former maximum nearer dusk and the latter nearer midnight. This combination suggests that the variation is due to an offset of the torus toward local midmorning, and perhaps that the cooling time is short. We also describe a general method for constraining solutions to be nonnegative when fitting data using the singular value decomposition least squares technique.
Precipitation of radiation belt electrons induced by obliquely propagating lightning‐generated whistlers
Authors: Lauben D. S. , Inan U. S. , Bell T. F.
Published: February 2004

A new combined ray tracing and test particle formulation is presented which calculates the spatiotemporal electron precipitation flux signatures at ionospheric altitudes induced by obliquely propagating lightning‐generated whistler waves. The formulation accounts for the variation in wave characteristics (frequency‐time dispersion, wave normal angle, and power density) as the whistler generated by an individual lightning discharge propagates through vast volumes of the magnetosphere in the absence of field‐aligned cold plasma density enhancements, and calculates the detailed gyroresonance scattering of trapped energetic electrons into the atmospheric loss cone over a broad range of field lines (L shells) to determine the precipitation flux over extensive ionospheric regions. Results show that peak precipitation flux patches (hotspots) several tens of degrees of latitude and longitude in size develop at locations ∼7° to ∼20° poleward of the discharge as a consequence of propagation paths which convey wave energy from lower to higher L shells. For oblique whistler intensities matching satellite observations (10 to 30 pT) peak flux levels of several milli‐ergs cm−2 s−1 are indicated, arriving as early as ∼ 1/4 s and lasting ∼1/2 s at lower observing latitudes (e.g., ∼32° for North American longitudes), while being delayed to ∼l s or more and lasting up to ∼2 s at higher latitudes (∼47°), creating a sense of poleward hotspot motion. Summary profiles integrated over time, latitude and L shell suggest that lightning‐generated oblique whistler‐induced electron precipitation deposits appreciable energy to the upper atmosphere at midlatitudes and contributes significantly to the loss of energetic (>100 keV) radiation belt electrons, particularly over 2.2 ≤ L ≤ 3.5 where the slot region forms.
Charged particle dynamics in a tangential discontinuity
Authors: Smets Roch
Published: February 2004

We investigate the regularity of particle motion in a magnetopause‐like magnetic field topology for a southward interplanetary magnetic field case. For that issue, a rotation of 180° of the magnetic field direction through the magnetopause is considered, while its total magnitude remains constant. Our main interest is to emphasize the different dynamical regimes for charged particles when their Larmor radii are of the order of the thickness of the magnetic field reversal layer. When the interface is a tangential discontinuity, it is shown that particle dynamics is regular, whereas the introduction of a small component of the magnetic field, normal to the interface, results in weakly stochastic dynamics. A new parameter κRL is introduced to organize the charged particle dynamics. When κRL is greater than 1, particle motion is adiabatic, and when κRL is smaller than 1, particle motion is nonadiabatic, its magnetic moment being possibly either damped or unchanged when interacting with the discontinuity. Implications for the pitch angle distribution of a population interacting with such a tangential discontinuity will be discussed.
Ionospheric disturbances observed by DMSP at middle to low latitudes during the magnetic storm of June 4–6, 1991
Authors: Burke W. J. , Rubin A. G. , Maynard N. C. , Gentile L. C. , Sultan P. J. , Rich F. J. , de La Beaujardière O. , Huang C. Y. , Wilson G. R.
Published: February 2004

This paper extends a recent study of electric field penetration into the inner magnetosphere observed by the Combined Release and Radiation Effects (CRRES) satellite and the Defense Meteorological Satellite Program (DMSP) satellite F8 during the magnetic storm of June 4–6, 1991, to consider its ionospheric consequences. Effects include the development of > 1 km/s subauroral ion drift (SAID) structures, the formation of midlatitude density troughs, and the vertical transport of equatorial plasma, bubbles. Nearly simultaneous auroral electron and plasma drift measurements were acquired by three DMSP satellites with F8 and F9 in one hemisphere and FlO in the other. Moderate to strong SAID structures were consistently detected for ∼10 hours during the early main phase of the storm. Weak SAIDs were encountered during ∼8 hours of the early recovery phase. DMSP data show that SAIDs with similar characteristics developed at magnetically conjugate locations and extended for at least 3 hours in local time. Simultaneous measurements show that the SAIDs spanned temporally grooving but latitudinally narrow plasma density troughs. These observations suggest that the magnetospheric sources of SAIDs act more like voltage than current generators. Energetic electron fluxes, electric fields, and plasma waves measured by CRRES indicate that during this storm the ring current shielding charges and SAID sources were located in regions of high plasma density characteristic of the plasmasphere. The sequence in which DMSP detected equatorial plasma density irregularities is consistent with model predictions that stormtime electrodynamics at low latitudes operate on distinctive fast and slow timescales [Fejer and Schcrliess, 1997].
“Atmospheric holes” are not small comets
Authors: Harris Alan W.
Published: February 2004

Frank and Sigwarth [1993, 1999] have promoted the hypothesis of a population of small “house‐sized” comets in near‐parabolic orbits that are nearly tangent with the Earth's and rain down on the Earth at a rate of ∼20/min. The hypothesis is based on “holes” in the dayglow of the Earth's atmosphere, which they first claimed to see in images from the Dynamics Explorer 1 satellite, and more recently in images from the Polar satellite. One of the key aspects of the claimed observations is that the atmospheric holes appear to be more numerous on the morning hemisphere of the Earth, to which Frank and Sigwarth draw analogy to radar meteors, which show a similar asymmetry. In this paper, I show that the distribution of orbits posited by Frank and Sigwarth yield a maximum flux in the afternoon, the opposite asymmetry from the claimed observations. The only orbits which yield the correct diurnal asymmetry, and preserve acceptably low entry speeds, are orbits interior to the Earth's having perihelia near the orbit of Mercury. Thus any relationship of “atmospheric holes” to “small comets,” or icy bodies from the outer solar system, can be ruled out.
Solar wind erosion of the Venus polar ionosphere
Authors: Pérez‐de‐Tejada H.
Published: February 2004

The geometry of the Venus nightside ionosphere is reexamined on the basis of plasma and magnetic field data obtained with the Pioneer Venus Orbiter (PVO) and the Mariner 5 spacecraft. There is evidence indicating that the shocked solar wind that streams over the magnetic polar regions of the Venus ionosphere experiences a sharp expansion and also a strong deceleration to speeds much smaller than those present in the outer ionosheath. It is argued that the deficiency of solar wind momentum that is inferred from the PVO and Mariner 5 measurements along the flanks of the Venus ionosheath may be responsible for the erosion of the polar upper ionosphere in plasma channels that extend downstream from the magnetic polar regions. The erosion of the Venus ionosphere is mostly produced within those channels and represents the main source of material delivered to the Venus wake. The configuration that is proposed accounts for the PVO observation of plasma clouds and ionospheric holes in the nightside hemisphere and leads to a mass loss smaller than that expected from a global erosion. The formation and evolution of the ionospheric polar channels should also be important in the solar wind interaction and erosion of the Mars ionosphere.
Optical and particle signatures of magnetospheric boundary layers near magnetic noon: Satellite and ground‐based observations
Authors: Oksavik K. , Søraas F. , Moen J. , Burke W. J.
Published: February 2004

In this paper we present a set of satellite and ground‐based observations suggesting that energetic magnetospheric electrons cannot be used as an unambiguous discriminator between open and closed field lines on the dayside. Using two data sets from the Defense Meteorological Satellite Program (DMSP) F13 and NOAA 12 satellites flying through dayside Type 1 cusp aurora (both close in time and space), we reach two apparently incompatible conclusions. Cusp/mantle precipitation, stepped cusp signatures, and antisunward convection in the DMSP F13 data set strongly suggest open magnetic field lines. On the other hand, NOAA 12 observed a mixture of magnetosheath and isotropic energetic particles. Trapped energetic electrons are traditionally regarded as being on closed flux. However, in addition to earlier proposed trapping on open field lines, we suggest that transmission lines connecting merging sites near the cusp in the Southern Hemisphere with the northern auroral ionosphere can be several tens of RE long. Alfvén wave transit times of several minutes may make it impossible to determine from satellite measurements in the ionosphere whether magnetic field lines threading low‐latitude boundary layer (LLBL) plasmas are open or closed. New research tools will be needed to unify understanding of complementary particle measurements from the DMSP and NOAA satellites.
Boundary‐oriented electron precipitation model
Authors: Sotirelis Thomas , Newell Patrick T.
Published: February 2004

A boundary‐oriented model of the global configuration of electrons precipitating into the polar ionosphere is presented. It provides the differential energy flux of precipitating electrons from 32 eV to 30 keV for five different activity levels. Data from 12 years and eight DMSP spacecraft were incorporated into the model. The defining characteristic of this model is that only observations similarly located relative to auroral boundaries (e.g., observations just equatorward of the open‐closed boundary) are averaged together. The model resulting from this approach more closely resembles instantaneous observations than previous efforts. A distinct polar cap surrounds a narrow auroral zone, transitions between different regions are appropriately sharp, and model spectra are more realistic. This increased fidelity with observation is a significant advantage for the model, broadening its applicability. Also new is the calculation of both mean and median model spectra. The mean is dominated by sporadic flux enhancements, where present, while the median resembles more commonly observed background fluxes, permitting both of these aspects to be addressed. Parameterization for activity is based on the degree of magnetotail stretching, as indicated by the latitude of the ion isotropy boundary. A variety of features can be discerned in the model. There is a large difference between the mean and median energy flux in regions where upward region 1 Birkeland currents are commonly observed. The smooth ∼1 to 10 keV precipitation seen at most local times, in the equatorward portion of the oval, is nearly absent in much of the afternoon sector. Enhanced number fluxes are seen at the poleward edge of the oval near midnight, likely due to the frequent presence of field‐aligned bursts. Structured precipitation dominates the energy flux at all local times except between dawn and noon, where the contribution from unstructured precipitation dominates. The total hemispheric energy flux due to mean spectra varies with activity from 6 to 38 GW and exceeds the energy flux due to median spectra by a factor of approximately 4, regardless of activity.
Three‐dimensional ray‐tracing for very low latitude whistlers, taking into account the latitudinal and longitudinal gradients of the ionosphere
Authors: Ohta Kenji , Hayakawa Masashi
Published: February 2004

Propagation mechanism of very low latitude (geomagnetic latitude less than 20°) whistlers is poorly understood, and this paper examines the propagation characteristics of nonducted propagation at very low latitudes by using three‐dimensional ray‐tracing for realistic ionosphere/magnetosphere models with latitudinal and longitudinal gradients and International Geomagnetic Reference Field (IGRF) magnetic model. By assuming small possible tilts (in the latitudinal and longitudinal direction) of the initial wave normal angle in the input Southern Hemisphere as in our previous paper [Ohta et al., 1997], we have found that it is possible for us to detect, at a very low latitude position in the Northern Hemisphere, some whistler rays being able to penetrate through the ionosphere and some others that are subject to total reflection and come back to the magnetosphere. By making full use of systematic analyses of ionospheric parameters (local time (LT) dependence of latitudinal and longitudinal gradients), we conclude that the LT dependence of occurrence rate of whistlers at very low latitudes can be accounted for by means of such LT dependence of the gradient (especially latitudinal), lending to a further support to our previous nonducted propagation mechanism.
Geotail observations of the Kelvin‐Helmholtz instability at the equatorial magnetotail boundary for parallel northward fields
Authors: Fairfield D. H. , Otto A. , Mukai T. , Kokubun S. , Lepping R. P. , Steinberg J. T. , Lazarus A. J. , Yamamoto T.
Published: February 2004

For several hours on March 24, 1995, the Geotail spacecraft remained near the duskside magnetotail boundary some 15 RE behind the Earth while the solar wind remained very quiet (V=330 km s−1, n=14–21 cm−3) with a very steady 11‐nT northward magnetic field. Geotail experienced multiple crossings of a boundary between a dense (n= 19 cm−3), cool (Tp=40 eV), rapidly flowing (V=310 km s−1) magnetosheath plasma and an interior region characterized by slower tailward velocities (V=100 km s−1), lower but substantial densities (n=3 cm−3) and somewhat hotter ions (220 eV). The crossings recurred with a roughly 3‐min periodicity, and all quantities were highly variable in the boundary region. The magnetic field, in fact, exhibited some of the largest fluctuations seen anywhere in space, despite the fact that the exterior magnetosheath field and the interior magnetosphere field were both very northward and nearly parallel. On the basis of an MHD simulation of this event, we argue that the multiple crossings are due to a Kelvin‐Helmholtz instability at the boundary that generates vortices which move past the spacecraft. A determination of boundary normals supports Kelvin‐Helmholtz theory in that the nonlinear steepening of the waves is seen on the leading edge of the waves rather than on the trailing edge, as has sometimes been seen in the past. It is concluded that the Kelvin‐Helmholtz instability is an important process for transferring energy, momentum and particles to the magnetotail during times of very northward interplanetary magnetic field.
Interferometric coherency determination of wavelength or what are broadband ELF waves?
Authors: Kintner P. M. , Franz J. , Schuck P. , Klatt E.
Published: February 2004

To determine the wavelength of waves within a random, isotropic wave field, we introduce the observable of wave coherency measured with plasma wave interferometers. We show generally that within a random direction wave field, wavelengths large compared to the interferometer length produce large coherency (nearly 1), but wavelengths the order of a few times the interferometer length, or smaller, produce small coherency (close to zero). We apply this principle first to examining auroral hiss and lower hybrid waves measured by the Physics of Auroral Zone Electrons (PHAZE) 2 and Topside Probe of the Auroral Zone (TOPAZ) 3 experiments and show that the implied wavelengths are consistent with the expected dispersion relations and with other, different estimates of wavelength for these modes. Next, we apply the principle to broadband extra low frequency (BB‐ELF) electric fields observed in both experiments and conclude that the wavelengths are small. In one case we calculate the coherency of BB‐ELF electric fields, using an ensemble average of 7889 data samples, and demonstrate that the coherency near the oxygen gyrofrequency is very small (≅0.15), corresponding to wavelengths of 10 m and the order of the ion gyroradius. We conclude that because of the short wavelengths, previous satellite measurements of BB‐ELF electric fields may have underestimated the electric field amplitudes, unless ion gyroradii are substantially larger than the case for these rocket measurements. Although the wavelengths and frequencies of BB‐ELF electric fields are now known, we are unable to assign the wave to a known, normal mode of homogeneous plasmas. This suggests that inhomogeneities may be essential for describing BB‐ELF electric fields.
The EUV airglow of Titan: Production and loss of
Authors: Stevens Michael H.
Published: February 2004

The N2 Carroll‐Yoshino (CY)
and (0,1) Rydberg bands between 95 and 99 nm were reported to be the most prominent EUV emission features in Voyager 1 ultraviolet spectrometer (UVS) airglow spectra from Titan's atmosphere. Although
is strongly excited by photoelectron impact, the (0,0) band is optically thick near peak production, so a multiple‐scattering model is employed to calculate (0,v″) nadir‐viewing intensities. The model accounts for all known loss processes and quantifies the redistribution of photons to (0,v″ > 0). Results show 7.6 R of (0,1) intensity, in agreement with reported observations (5–10 R), and 0.2 R of (0,0), in spectacular disagreement with reported observations (6–10 R). Nadir‐viewing intensities of all other expected NI multiplets and N2 bands in the brightest portion of the EUV airglow spectrum (92.0–101.5 nm) are also calculated using photodissociative ionization of N2 and photoelectron impact on N2. It is found that NI multiplets and N2 bands near (0,0) and unresolved by the UVS combine to produce 8.3 R, consistent with that reported for (0,0) and indicating that it was misidentified in previous analyses. The Ultraviolet Imaging Spectrograph (UVIS) on Cassini should unambiguously distinguish any (0,0) intensity from the brightest features nearby.
Mini‐Magnetospheric Plasma Propulsion: Tapping the energy of the solar wind for spacecraft propulsion
Authors: Winglee R. M. , Slough J. , Ziemba T. , Goodson A.
Published: February 2004

Mini‐Magnetospheric Plasma Propulsion is a potentially revolutionary plasma propulsion concept that could enable spacecraft to travel out of the solar system at unprecedented speeds of 50 to 80 km s−1 or could enable travel between the planets for low power requirements of ∼l kW per 100 kg of payload and ∼0.5 kg fuel consumption per day for acceleration periods of several days to a few weeks. The high efficiency and specific impulse attained by the system are due to its utilization of ambient energy, in this case the energy of the solar wind, to provide the enhanced thrust. Coupling to the solar wind is produced through a large‐scale magnetic bubble or mini‐magnetosphere generated by the injection of plasma into the magnetic field supported by solenoid coils on the spacecraft. This inflation is driven by electromagnetic processes, so that the material and deployment problems associated with mechanical sails are eliminated.
Interplanetary magnetic field connection to the L1 Lagrangian orbit during upstream energetic ion events
Authors: Haggerty D. K. , Roelof E. C. , Smith C. W. , Ness N. F. , Tokar R. L. , Skoug R. M.
Published: February 2004

Energetic ions (>15 keV) moving upstream from the Earth's bow shock frequently appear at the sunward Lagrangian point (L1) ∼1.5 × 106 km upstream from Earth. The most common orientation of the interplanetary magnetic field (IMF) at L1 during these upstream events is near‐radial from the Sun (the nominal direction for connection to the magnetosphere). However, strong unidirectional beams of ions streaming away from Earth, consistent with good magnetic connection to the bow shock, are observed even when the IMF is transverse to the radial direction. This study includes for the first time observations of upstream events from as many as four upstream spacecraft. Included in this report are energetic ion and magnetic field measurements from (1) ACE/Electron, Proton, and Alpha Monitor (EPAM) and ACE/Magnetometer Instrument (MAG); (2) Wind/Three‐Dimensional Plasma Analyzer (3DP) and Wind/Magnetic Fields Investigation (MFI); (3) IMP 8/Energetic Particle Experiment (EPE) and IMP 8/MAG; and (4) Geotail/Energetic Particle and Ion Composition (EPIC) and Geotail/MAG. In addition, the ACE/Solar Wind Electron, Proton, and Alpha Monitor (SWEPAM) instrument identifies IMF connection between the L1 point and the Earth's bow shock by the presence of low‐energy (272‐372 eV) bidirectional electron flux. Instruments on the IMP 8 and Geotail spacecraft simultaneously measure the energetic ion intensity and IMF configuration close to the Earth's bow shock during times of particle enhancements observed at L1. Analysis of ACE, Wind, IMP 8, and Geotail observations from February through November 1998 shows that >40% of upstream events are observed during times of nonradial (>30° from the GSE X axis) IMF orientation. A second and independent study of ACE/EPAM observations of over 500 upstream energetic ion events from launch through November 1998 confirms this result. We find similar distributions of radial and nonradial IMF orientations both close to the bow shock and at L1. This implies that the IMF configurations during upstream events are large‐scale spatial structures with radii of curvature of the order of the Earth‐L1 distance, i.e., 0.01 AU. These spatial structures are being convected through the L1 point into the Earth's foreshock.
On the magnetospheric source regions of substorm‐related field‐aligned currents and auroral precipitation
Authors: Lu G. , Brittnacher M. , Parks G. , Lummerzheim D.
Published: February 2004

This paper presents a detailed analysis of field‐aligned currents and auroral UV emissions during an isolated substorm on January 9, 1997. The large‐scale upward field‐aligned currents derived from the assimilative mapping of ionospheric electrodynamics (AMIE) procedure are found to generally coincide with the relatively intense auroral emissions in the central auroral oval, and downward field‐aligned currents are mostly in the poleward edge (and with much weaker downward currents at the equatorward edge) of the auroral oval where auroral luminosity is considerably lower. However, the brightest, yet localized, discrete auroras shown in the UV images often lie at the boundary between upward and downward field‐aligned currents, indicating that the current AMIE spatial resolution is unable to resolve the fine‐scale filamentary field‐aligned currents that are expected to be associated with the localized auroral features. The initial auroral brightening at the substorm onset occurs near the midnight region; intense auroral precipitation then appears to shift toward dusk and to higher latitudes in the ionosphere as the substorm proceeds. Using an improved time‐dependent magnetic field model specified for this event, we find that the initial auroral intensification at the substorm onset maps to the inner central plasma sheet between −5 and −7 RE, with its earthward edge located just outside of the plasmapause. During the substorm expansion phase, the corresponding magnetospheric source region of auroral precipitation moves slightly tailward and toward the dusk flank near the low‐latitude boundary layer. At the late stage of the expansion phase, bright discrete auroras map to a narrow region of tailward plasma convection that is embedded in a wide and predominantly earthward convection zone. The mapping of substorm‐related field‐aligned currents, on the other hand, is more confined close to the Earth, with the current density peaks around geosynchronous altitude. The apparently different magnetospheric source regions imply that the processes that produce energetic precipitating particles are not the same ones that generate the strongest magnetic perturbations in the magnetosphere. The relative importance of electrostatic fields and the inductive electric fields during the substorm expansion phase is also investigated. It is shown that the inductive electric fields are comparable to or even larger in magnitude than the electrostatic fields at the early expansion phase, but they become less important at the late stage of the substorm expansion phase.
Energetic proton observations at 1 and 5 AU: 2. Rising phase of the solar cycle 23
Authors: Lario D. , Marsden R. G. , Sanderson T. R. , Maksimovic M. , Sanahuja B. , Plunkett S. P. , Balogh A. , Forsyth R. J. , Lin R. P. , Gosling J. T.
Published: February 2004

The increasing level of solar activity at the end of 1997 coincides with the observation of solar energetic particle (SEP) events by the Wind and Ulysses spacecraft. The proximity of Ulysses to the ecliptic plane during this period allows us to study the effects of the solar activity at two different heliolongitudinal and heliocentric distances but at similar heliolatitudes. We identify the main transient proton enhancements seen by Wind and Ulysses from October 1997 to the end of December 1998. We compare their characteristics and suggest an interpretation in terms of their heliospheric location, the activity occurring at the Sun, and the conditions for particle propagation between the Sun and both spacecraft. Whereas at 1 AU different SEP events can be associated with individual coronal mass ejections (CMEs), at 5 AU long‐lasting SEP events are observed while a sequence of CMEs takes place at the Sun. Continuous injection of particles from traveling CME‐driven shocks, the effects of particle propagation along interplanetary magnetic field lines, and the corotation of these field lines across the Ulysses location are the main factors responsible for these long‐lasting periods of high particle intensity observed by Ulysses.
Modeling the N2 Lyman‐Birge‐Hopfield bands in the dayglow: Including radiative and collisional cascading between the singlet states
Authors: Eastes Richard W.
Published: February 2004

A new model for the daytime airglow emissions from the N2 Lyman‐Birge‐Hopfield (LBH) bands (a1Πg–X1Σ+g) in the Earth's atmosphere is presented. This model gives good agreement, which other first principles models have been unable to obtain, with dayglow observations reporting increased vibrational populations, relative to direct excitation, for v ≤1 of the N2 a1Πg state. The ability of the model to match the observations is due to the inclusion of radiative and collisional cascading between the singlet states. Such cascading was not included in previous first principles dayglow calculations for the singlet states. Not only does cascading improve the fit between the observed and modeled relative vibrational populations, it also increases the total emission from the LBH bands by a factor of ∼1.6 due to the transfer of excitation from the a′ and w states to the a state, resulting in significantly greater emission than predicted by earlier models using the same excitation cross section for the a state. Such an increase in the total emission from the LBH bands is consistent with recent work by Budzien et al. [1994] and Link et al. [1994]. The coupling between the singlet states will have a significant impact on the interpretation of the LBH band emissions from the Earth's atmosphere.
Toward the theory of magnetospheric magnetosonic eigenoscillations: simple theoretical models
Authors: Leonovich A. S. , Mazur V. A.
Published: February 2004

The structure of magnetosonic eigenmodes was investigated analytically within the framework of simple two‐ and three‐dimensionally inhomogeneous models. Asymptotic (in the limit m ≫ 1, where m is azimuthal wave number) expressions were obtained for the eigenfrequency spectrum of magnetosonic oscillations in the cavity resonator under the plasmapause, as well as for outer magnetospheric cavity modes, the outer boundary for which is represented by the magnetopause. These oscillations were found to be damped ones. Furthermore, the damping of the eigenoscillations in the cavity under the plasmapause is caused by the escape of some of their energy through the potential barrier to the outer magnetosphere. The damping of the outer magnetospheric cavity modes is due to the fact that the magnetopause represents a partially reflecting boundary, through which a part of the oscillation energy escapes to the solar wind. In terms of an axisymmetric model of the magnetosphere, asymptotic (when m ≫ 1) expressions were obtained for damping decrements of the eigenmodes. The spatial structure of magnetosonic eigenmodes was investigated in a simple three‐dimensionally inhomogeneous model of the magnetosphere. The asymptotic expression was obtained for the spectrum of their eigenfrequencies.
Theoretical properties of electromagnetic ion cyclotron waves in the terrestrial, dayside, low‐latitude plasma depletion layer under uncompressed magnetosheath conditions
Authors: Gnavi Graciela , Gratton Fausto T. , Farrugia Charles J.
Published: February 2004

We present a numerical study of electromagnetic ion cyclotron wave (EICW) activity (growth and damping) in the terrestrial plasma depletion layer (PDL) under typical solar wind conditions. Aside from the α particles, all parameters in this study are as measured by AMPTE/IRM during 13 magnetosheath passes under low magnetic shear made in 1984–1985 and calculated with the superposed epoch analysis technique [Phan et al., 1994]. Three locations within the PDL are specified using minutes before the key time identifying the magnetopause crossing in the superposed epoch analysis (O, —5, —10 min). Our work thus characterizes average properties of EICWs along radial profiles in the PDL in the magnetic latitude and local time ranges of ±30° and 0800 to 1600 hours, respectively. In order to study the situation in the subsolar region more closely, we calculate also with PDL parameters acquired by AMPTE/IRM during the pass nearest to local noon (October 24, 1985). For α particle parameters we take reasonable estimates but also study the effect of varying the α particle temperature anisotropy. The influence of a small α particle‐proton relative drift is also included. At the magnetopause we find one peak of activity in the frequency range from 0.2 to 0.3 Ωp (the proton cyclotron frequency), which is thus below the resonance frequency of the α particles (0.5 Ωp). At locations 10 min and 5 min prior to the magnetopause crossing, the activity spectrum bifurcates, with both peaks below the a resonance and separated by an absorption band. Our explanation of this result is that as we move away from the magnetopause, the increasing plasma β enables the protons to overcome the α absorption. With a relative α particle‐proton drift of 10% of the local Alfvén speed, the absorption band is removed, but all excited frequencies are still less than 0.5 Ωp. The absorption band may also be removed by a high α particle thermal anisotropy coupled with a low α particle β along the magnetic field. On October 24, 1985, the PDL was characterized by a wider variation of β and a larger proton temperature anisotropy. Under these conditions a second EICW activity peak appears between 0.5 and 0.6 Ωp at the two locations away from the magnetopause, in addition to the α peak mentioned above, which we ascribe to the larger anisotropy of the protons. Again, a small α particle drift can remove the activity minimum. With the stagnation line flow pattern in the PDL found by AMPTE/IRM on these passes, we hypothesize that EICWs excited near noon subsequently travel along the magnetic field, bringing EICW activity to high latitudes. However, EICWs generated away from noon will be damped out while being carried to the magnetopause flanks.
Heliospheric modulation of cosmic ray protons: Role of enhanced perpendicular diffusion during periods of minimum solar modulation
Authors: Potgieter Marius S.
Published: February 2004

The effect of enhanced perpendicular diffusion in the polar regions of a simulated heliosphere seems required in drift models for the modulation of galactic cosmic rays in order to find a latitude dependence of cosmic ray protons in the inner heliosphere that is compatible with Ulysses observations. This effect was studied in detail to establish how important it is and to understand the role it plays in global cosmic ray modulation, particularly during minimum modulation periods. After searching through a large parameter space, it was found that enhanced perpendicular diffusion was indeed necessary to obtain compatibility with observations in the inner heliosphere, especially during A > O magnetic field polarity epochs (e.g., from 1990 to ∼2000). This approach, however, also increased the radial dependence during this epoch. Switching to A < O epochs (e.g., from ∼1981 to 1989), the same set of parameters did not fit the observed 1987 radial dependence for 200 MeV cosmic ray protons, so a completely different set of diffusion coefficients had to be used, including less enhanced perpendicular diffusion. Apart from a polarity difference, minimum modulation conditions and, by implication, the diffusion tensor seem to be different during A > O and A < O solar minimum modulation periods.
Magnetosheath response to the interplanetary magnetic field tangential discontinuity
Authors: Šafránková J. , Přech L. , Němeček Z. , Sibeck D. G. , Mukai T.
Published: February 2004

We present a multipoint observational study of the magnetosheath response to the interplanetary magnetic field tangential discontinuities which form hot flow anomaly‐like (HFAs) structures. We identify these structures in the vicinity of the bow shock as well as deeper in the magnetosheath. Two or more points of simultaneous observations allow us to describe the gradual evolution and propagation of these HFAs through the magnetosheath. From tens of events recorded by INTERBALL‐1, we present two cases. In the first, GEOTAIL identified HFAs in the solar wind near the bow shock, and INTERBALL‐1 and MAGION‐4 observed related events in the magnetosheath. During the second interval, all three spacecraft observed the HFA features in the magnetosheath. Our analysis of reported events suggests the negligible evolution of these structures in the magnetosheath. A survey of the INTERBALL‐1 data has shown that magnetosheath HFAs are observed predominantly during periods of fast solar wind.
Cyclotron resonance in coronal holes: 3. A five‐beam turbulence‐driven model
Authors: Hollweg Joseph V.
Published: February 2004

Following Hollweg and Johnson [1988], Isenberg [1990], and Li et al. [1999a], we postulate that the Sun launches a flux of low‐frequency Alfvén waves, which dissipate via a turbulent cascade to high frequencies where the energy is absorbed by ion cyclotron resonant interactions. The plasma consists of two proton beams, which are proxies for the resonant and nonresonant halves of their distribution function, two He++ beams, which are proxies for the strongly and weakly resonant halves of their distribution, and a single beam of O+5 with vanishing density. The level of the power spectrum at the high resonant frequencies is determined by the condition that the protons and He++ resonantly absorb energy at the same rate at which the low‐frequency waves are dissipating. Once the level of the high‐frequency power spectrum is determined, the resonant heating and acceleration of the O+5 can be calculated. For both Kolmogorov and Kraichnan scalings of the turbulent dissipation the model yields results for the protons that are in reasonably good agreement with the UVCS/SOHO results. The He++ becomes more than mass proportionally heated and flows faster than the protons, close to the Sun. However, our model is unable to reproduce the UVCS/SOHO observation that the O+5 temperature is still increasing with heliocentric distance r out to 3.5 rs. Instead, the O+5 becomes very hot initially, experiences a strong mirror force, and accelerates to high speed, which in turn leads to rapid adiabatic cooling. Put another way, the O+5 observations imply that (dT⊥/dt)res must be an increasing function of r, while it is the nature of the resonant interactions to make (dT⊥/dt)res decrease with increasing r.
Plasmoid ejection and auroral brightenings
Authors: Ieda A. , Fairfield D. H. , Mukai T. , Saito Y. , Kokubun S. , Liou K. , Meng C.‐I. , Parks G. K. , Brittnacher M. J.
Published: February 2004

Geotail plasma and magnetic field observations of 24 plasmoids between 21 and 29 RE have been compared with Polar ultraviolet observations of auroral brightenings. Both single and multiple plasmoids almost always corresponded to brightenings, but the brightenings were sometimes weak and spatially limited and did not always grow to a global substorm. Even a case where a plasmoid event occurred with fast postplasmoid flow corresponded to a weak brightening but no substorm. Some brightenings did not correspond to plasmoids, but these brightenings were observed away from the longitude of Geotail, indicating that plasmoids have a small longitudinal extent in the near tail. The plasmoids were occasionally observed before the brightenings but more frequently were observed 0–2 min after the brightenings, with the delays probably due to the transit time to the observation point. It seems likely that formation of a near‐Earth neutral line causes each brightening in the polar ionosphere, but these formations do not always lead to a full‐fledged substorm. What additional circumstance causes development of a full, large‐scale substorm remains an open question.