bluuebunny/crossref_metadata_2025 huggingface dataset:
Estrogen provision by reactive glia decreases apoptosis in the zebra finch (Taeniopygia guttata)
Authors: Saldanha Colin J. , Rohmann Kevin N. , Coomaralingam Luckshman , Wynne Ryan D.
Published: April 2005

Upregulation of aromatase (estrogen synthase) in glia around the site of neural injury may limit neural degeneration. Systemic administration of estrogen limits neural damage, but the specific role of local estrogen provision in this effect is unclear. In male zebra finches, we tested the effect of local aromatase inhibition and estrogen replacement on type of cellular degeneration and the distance of this degeneration from the source of insult. Subjects received injections of the aromatase inhibitor fadrozole into one telencephalic lobe and fadrozole and estradiol into the contralateral lobe. Seventy‐two hours later, we used Fluoro‐Jade B and TUNEL to label dying and apoptotic cells, respectively. Since each subject was its own control, we were able to assess the influence of local estrogen replacement in relative distinction from circulating steroids and constitutive aromatization. Cellular degeneration around the lesion was measured with Fluoro‐Jade B, TUNEL, and indirectly with aromatase expression. Additionally, the glial nature of aromatase‐positive cells around the injury was queried by co‐localization with vimentin. The estrogen replaced injury had fewer apoptotic cells clustered more closely around the injury compared to the hemisphere injected with fadrozole alone. Since Fluoro‐Jade B and TUNEL labeled similar numbers of cells, and the distance of these cells from the injection was identical, we suggest that estrogen replacement functions primarily to restrict apoptosis in the current paradigm. Lastly, aromatase‐positive cells around injuries co‐localize vimentin, establishing their glial nature. Thus, glial estrogen provision at sites of neural insult may be critical in limiting the cellular degeneration caused by injury via an inhibition of apoptosis. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005
Living radical photopolymerization induced grafting on thiol–ene based substrates
Authors: Reddy Sirish K. , Sebra Robert P. , Anseth Kristi S. , Bowman Christopher N.
Published: April 2005

The formation of reactive substrates with iniferter‐mediated living radical photopolymerization is a powerful technique for surface modification, which can readily be used to facilitate the incorporation of a variety of surface functionalities. In this research, the photopolymerization kinetics of novel bulk thiol–ene systems have been compared with those of typical acrylate and methacrylate systems when polymerized in the presence of the photoiniferter p‐xylene bis(N,N‐diethyl dithiocarbamate) (XDT). In the presence of XDT, the thiol–ene systems photopolymerize more quickly than the traditional acrylate and methacrylate systems by one to two orders of magnitude. Fourier transform infrared spectroscopy has been used to monitor the photografting kinetics of various monomers on dithiocarbamate‐functionalized surfaces. Furthermore, this technique has been used to evaluate surface‐initiation kinetics and to emphasize the influence of bulk substrate properties on grafting kinetics. Finally, photopatterning has been demonstrated on a dithiocarbamate‐incorporated thiol–ene substrate with conventional photolithographic techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2134–2144, 2005
Synthesis of polymeric microspheres from a Merrifield resin by surface‐initiated nitroxide‐mediated radical polymerization
Authors: Bian Kejian , Cunningham Michael F.
Published: April 2005

Polymeric microspheres were prepared from a Merrifield resin via nitroxide‐mediated radical polymerization. Polystyrene, poly(acetoxystyrene), and poly[styrene‐b‐(methyl methacrylate‐co‐styrene)], poly(acetoxystyrene‐b‐styrene), and poly(styrene‐co‐2‐hydroxyethyl methacrylate) copolymers were demonstrated to graft onto 2,2,6,6‐tetramethyl‐1‐piperidinyloxy nitroxide bound Merrifield resins. The polymerization control was enhanced both on the surface and in solution by the addition of sacrificial nitroxide. The significant increase in the particle diameter (more than a fivefold volume increase for polystyrene brushes) showed that polymer growth was not only on the surface but also within the particles, and this diameter increase could be adjusted through changes in the molecular weight of the polymers. The microspheres were characterized by elemental analysis, IR spectroscopy, particle size analysis, and optical microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2145–2154, 2005
Development of detailed action plans in the event of a sodium hydride spill/fire
Authors: Fluegeman Claire , Hilton Timothy , Moder Kenneth P. , Stankovich Robert
Published: April 2005

The Center for Chemical Process Safety (CCPS) has developed a process for managing chemical reactivity hazards, such as water‐reactive/pyrophoric sodium hydride. This coupled with a recent fire while handling sodium hydride, at a pharmaceutical production facility, revealed gaps in the handling and emergency response process as well as in the emergency response materials used for spills of sodium hydride. A detailed action plan (DAP) was developed for personnel handling sodium hydride, as well as emergency first responders. The DAP identified actions in the event of a spill or fire for material handlers, emergency first responders, and the subsequent safe disposition of the contained material. Development of the DAP for sodium hydride required in‐house testing of various fire‐extinguishing agents and the benchmarking of best practices within the pharmaceutical and chemical industries. The optimum method or template chosen to develop the DAP was adaptable to conditions both in warehouses and in production buildings. Laboratory testing followed by field testing with up to 0.5 kg of sodium hydride identified damp sand in combination with liquid nitrogen as the superior agents to smother, contain, and permit transport to a suitable disposition area for destruction of unreacted sodium hydride. The template and method used to create the sodium hydride DAP may have applications for other water‐reactive/pyrophoric reagents.

The use of wet sand with liquid nitrogen as a smothering agent promises to be a unique and potentially breakthrough method for smothering and transporting spilled water‐reactive/pyrophoric reagents. Additional testing is planned for other water‐reactive/pyrophoric reagents to assess the use of these emergency response materials and to develop additional DAPs. © 2005 American Institute of Chemical Engineers Process Saf Prog
First‐principles study on atom order and stability of GaInS3(CdS)m natural superlattices
Authors: Ishikawa Masato , Nakayama Takashi
Published: April 2005

GaInS3(CdS)m is the layered natural superlattice system made of the combination of II–VI and III–VI group semiconductors. Atom order of this system was investigated by using the first‐principles calculation. It was shown that the CdS layers are located inside the GaInS3 layers when their thickness is small, m < 2, while they are located outside the GaInS3 as their thickness increases, large than m = 2. This change of atom order occurs due to the electric field between GaS and InS layers and causes the band‐gap variation as a function of the CdS layer thickness. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrathin metal layers to convert surface polarity of nitride semiconductors
Authors: Nakayama T. , Mikami J.
Published: April 2005

The possibility of the surface‐polarity conversion of AlN upon the deposition of ultrathin Al metal layers is investigated by the first‐principles theoretical calculations. It is shown that, reflecting the crystal structures of underlying layers and the binding‐energy difference between Al–N and Al–Al bonds, the surface‐polarity conversion from N‐face to Al‐face polarity becomes possible only when the deposited Al metal layers have wurtzite structure and two‐monolayer thickness. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anatoxins and degradation products, determined using hybrid quadrupole time‐of‐flight and quadrupole ion‐trap mass spectrometry: forensic investigations of cyanobacterial neurotoxin poisoning
Authors: James Kevin J. , Crowley Janet , Hamilton Brett , Lehane Mary , Skulberg Olav , Furey Ambrose
Published: April 2005

The potent neurotoxins from cyanobacteria, anatoxin‐a (AN), its methyl analogue, homoanatoxin‐a (HMAN), and their degradation products, have been studied using nano‐electrospray hybrid quadrupole time‐of‐flight mass spectrometry (QqTOF‐MS). The anatoxin degradation products, which are readily produced in vivo by either reduction or epoxidation, were also examined in this study. The high mass accuracy QqTOF‐MS data was used to confirm formula assignments for major product ions and quadrupole ion‐trap (QIT)‐MS was used to construct fragmentation pathways for anatoxins. Significant differences between these fragmentation pathways were observed. Comparisons between the spectra of compounds that differ in side‐chain length (the AN and HMAN series) were used to identify ions that are characteristic of the homologues. The application to forensic samples in which the principal neurotoxin had undergone rapid biodegradation has been demonstrated and used to confirm anatoxin poisoning of dogs. Copyright © 2005 John Wiley & Sons, Ltd.
Determination of 2‐methoxyestradiol in human plasma, using liquid chromatography/tandem mass spectrometry
Authors: Lakhani Nehal J. , Lepper Erin R. , Sparreboom Alex , Dahut William L. , Venitz Jürgen , Figg William D.
Published: April 2005

A liquid chromatography/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of 2‐methoxyestradiol (2ME2) in human plasma. Sample pretreatment involved liquid‐liquid extraction with ethyl acetate of 0.3‐mL aliquots of plasma spiked with the internal standard, deuterated 2ME2 (2ME2‐d5). Separation was achieved on a Zorbax Eclipse® C18 column (2.1 × 50 mm, i.d., 5 μm) at room temperature using a gradient elution with methanol and water at a flow rate of 0.25 mL/min. Detection was performed using atmospheric pressure chemical ionization MS/MS by monitoring the ion transitions from m/z 303.1 → 136.8 (2ME2) and m/z 308.1 → 138.8 (2ME2‐d5). Calibration curves were linear in the concentration range of 1–100 ng/mL. The accuracy and precision values, obtained from three different sets of quality control samples analyzed in quintuplicate on four separate occasions, ranged from 105–108% and from 3.62–5.68%, respectively. This assay was subsequently used for the determination of 2ME2 concentration in plasma of a patient with cancer after a single oral administration of 2ME2 at a dose of 2200 mg. Copyright © 2005 John Wiley & Sons, Ltd.
Continuum percolation with steps in the square or the disc
Authors: Balister Paul , Bollobás Béla , Walters Mark
Published: April 2005

In 1961 Gilbert defined a model of continuum percolation in which points are placed in the plane according to a Poisson process of density 1, and two are joined if one lies within a disc of area A about the other. We prove some good bounds on the critical area Ac for percolation in this model. The proof is in two parts: First we give a rigorous reduction of the problem to a finite problem, and then we solve this problem using Monte‐Carlo methods. We prove that, with 99.99% confidence, the critical area lies between 4.508 and 4.515. For the corresponding problem with the disc replaced by the square we prove, again with 99.99% confidence, that the critical area lies between 4.392 and 4.398. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005
Steady state analysis of balanced‐allocation routing
Authors: Anagnostopoulos Aris , Kontoyiannis Ioannis , Upfal Eli
Published: April 2005

We compare the long‐term, steady‐state performance of a variant of the standard Dynamic Alternative Routing (DAR) technique commonly used in telephone and ATM networks, to the performance of a path‐selection algorithm based on the “balanced‐allocation” principle [Y. Azer, A. Z. Broder, A. R. Karlin, and E. Upfal, SIAM J Comput 29(1) (2000), 180–200; M. Mitzenmacher, Ph.D. Thesis, University of California, Berkeley, August 1996]; we refer to this new algorithm as the Balanced Dynamic Alternative Routing (BDAR) algorithm. While DAR checks alternative routes sequentially until available bandwidth is found, the BDAR algorithm compares and chooses the best among a small number of alternatives. We show that, at the expense of a minor increase in routing overhead, the BDAR algorithm gives a substantial improvement in network performance, in terms both of network congestion and of bandwidth requirement. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005
Is fetal cerebral vascular resistance affected by the presence of nuchal cord(s) in the third trimester of pregnancy?
Authors: Sherer D. M. , Sokolovski M. , Dalloul M. , Khoury‐Collado F. , Abulafia O.
Published: April 2005

Objective

To assess whether fetal cerebral vascular resistance is affected by the presence of nuchal cord(s) in the third trimester.

Methods

A set of 115 patients with well‐established dates and singleton, appropriate for gestational age (GA), non‐anomalous fetuses with nuchal cord(s) diagnosed with prenatal color Doppler imaging, between 28 and 41 weeks and 115 controls matched for GA, were studied. Patients with hypertension, diabetes and autoimmune conditions were excluded. Doppler indices were obtained from the umbilical artery (UA) and the fetal middle cerebral artery (MCA) upon initial diagnosis of the nuchal cord.

Results

Of 115 GA‐matched pairs of pregnancies, 103 fetuses had a single nuchal cord and 12 a double nuchal cord. No significant differences were noted in patient age, gravidity, parity, sonographically estimated fetal weight (SEFW), and growth centile at ultrasonographic diagnosis. Mean UA systolic/diastolic ratio (S/D) was 2.28 ± 0.32 and 2.36 ± 0.33 (P = 0.03) and UA resistance index (RI) 0.55 ± 0.06 and 0.57 ± 0.06 (P = 0.02) among study and controls, respectively. Mean fetal MCA S/D and RI did not differ significantly between the two groups (fetal MCA S/D 5.01 ± 1.28 and 5.04 ± 1.71 (P = 0.86), and mean fetal MCA RI 0.78 ± 0.06 and 0.78 ± 0.05 (P = 0.88)). No significant differences were noted in GA at delivery, incidence of meconium‐stained amniotic fluid, birth weight, mode of delivery, neonatal gender, 1 and 5 minute Apgar scores, or UA pH and base excess, between study and control patients.

Conclusion

Fetal cerebral vascular resistance is not affected by the presence of nuchal cord(s) in the third trimester of pregnancy. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
A Festschrift Honoring Norman M. Rich
Authors: Burris David G. , Sturtz Donald L. , Sheldon George F. , Blaisdell F. William
Published: April 2005

A Festschrift honoring forty years of government services, twenty‐five years as Founding Chairman of the Department of Surgery at the F. Edward Hébert School of Medicine of the Uniformed Services University of the Health Sciences, Bethesda, Maryland and the seventieth birthday of Norman M. Rich, MD, Facs, DMCC, was held on Friday 26 March, 2004 in conjuction with the 24th Annual USU Surgical Associates Day. This article describes that event and introduces the articles written in celebration of it. 

From a private collection.

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From a private collection.

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Simultaneous auroral observations described in the historical records of China, Japan and Korea from ancient times to AD 1700
Authors: Willis D. M. , Stephenson F. R.
Published: April 2005

Abstract. Early auroral observations recorded in various oriental histories are examined in order to search for examples of strictly simultaneous and indisputably independent observations of the aurora borealis from spatially separated sites in East Asia. In the period up to ad 1700, only five examples have been found of two or more oriental auroral observations from separate sites on the same night. These occurred during the nights of ad 1101 January 31, ad 1138 October 6, ad 1363 July 30, ad 1582 March 8 and ad 1653 March 2. The independent historical evidence describing observations of mid-latitude auroral displays at more than one site in East Asia on the same night provides virtually incontrovertible proof that auroral displays actually occurred on these five special occasions. This conclusion is corroborated by the good level of agreement between the detailed auroral descriptions recorded in the different oriental histories, which furnish essentially compatible information on both the colour (or colours) of each auroral display and its approximate position in the sky. In addition, the occurrence of auroral displays in Europe within two days of auroral displays in East Asia, on two (possibly three) out of these five special occasions, suggests that a substantial number of the mid-latitude auroral displays recorded in the oriental histories are associated with intense geomagnetic storms.Key words. Magnetospheric physics (auroral phenomena; storms and substorms)
Spatial distribution of upstream magnetospheric ≥50 keV ions
Authors: Anagnostopoulos G. C. , Argyropoulos G. , Kaliabetsos G.
Published: April 2005

Abstract. We present for the first time a statistical study of \\geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1) a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT) of the bow shock, (2) highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF) configuration, and (3) a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1) preferential leakage of ~50 keV magnetospheric ions from the dusk magnetopause, (2) nearly scatter free motion of ~50 keV ions within the magnetosheath, and (3) final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV) upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between ~16%-~34% in the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks)
The synthesis of travelling ionospheric disturbance (TID) signatures in HF radar observations using ray tracing
Authors: Stocker A. J. , Arnold N. F. , Jones T. B.
Published: April 2005

Abstract. Characteristic signatures are often observed in HF radar range-time-intensity plots when travelling ionospheric disturbances (TIDs) are present. These signatures, in particular the variation of the F-region skip distance, have been synthesised using a ray tracing model. The magnitude of the skip variation is found to be a function of the peak electron density perturbation associated with the TID and radar frequency. Examination of experimental observations leads to an estimate of the peak electron density perturbation amplitude of around 25% for those TIDs observed by the CUTLASS radar system. The advantage of using the skip variation over the radar return amplitude as an indicator of density perturbation is also discussed. An example of a dual radar frequency experiment has been given. The investigation of the effect of radar frequency on the observations will aid the optimisation of future experiments..Key words. Ionosphere (auroral ionosphere; ionosphere -atmosphere interactions; ionospheric disturbances)
The response of the azimuthal component of the ionospheric electric field to auroral arc brightening
Authors: Safargaleev V. , Lyatsky W. , Gazey N. G. , Smith P. N. , Kriviliov V.
Published: April 2005

Abstract. We have analyzed the response of azimuthal component of the ionospheric electric field to auroral arc activity. We have chosen for analysis three intervals of coordinated EISCAT and TV observations on 18 February, 1993. These intervals include three kinds of arc activity: the appearance of a new auroral arc, the gradual brightening of the existing arc and variations of the arc luminosity. The arcs were mostly east-west aligned. In all cases, the enhancement of arc luminosity is accompanied by a decrease in the westward component of the ionospheric electric field. In contrast, an increase of that component seems to be connected with arc fading. The observed response is assumed to have the same nature as the "short circuit" of an external electric field by the conductor. The possible consequence of this phenomenon is discussed..Keywords. Ionosphere (electric fields and currents; ionospheric irregularities) · Magnetospheric physics (auroral phenomena)
Latitudinal and longitudinal dispersion of energetic auroral protons
Authors: Lorentzen D. A.
Published: April 2005

Abstract. Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300-350 km) and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.Key words. Ionosphere (auroral ionosphere; · particle precipitation) · Space plasma physics · (transport processes)
The development of a regional geomagnetic daily variation model using neural networks
Authors: Sutcliffe P. R.
Published: April 2005

Abstract. Global and regional geomagnetic field models give the components of the geomagnetic field as functions of position and epoch; most utilise a polynomial or Fourier series to map the input variables to the geomagnetic field values. The only temporal variation generally catered for in these models is the long term secular variation. However, there is an increasing need amongst certain users for models able to provide shorter term temporal variations, such as the geomagnetic daily variation. In this study, for the first time, artificial neural networks (ANNs) are utilised to develop a geomagnetic daily variation model. The model developed is for the southern African region; however, the method used could be applied to any other region or even globally. Besides local time and latitude, input variables considered in the daily variation model are season, sunspot number, and degree of geomagnetic activity. The ANN modelling of the geomagnetic daily variation is found to give results very similar to those obtained by the synthesis of harmonic coefficients which have been computed by the more traditional harmonic analysis of the daily variation.Key words. Geomagnetism and paleomagnetism (time variations; diurnal to secular) · Ionosphere (modelling and forecasting)
Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar
Authors: Endo M. , Fujii R. , Ogawa Y. , Buchert S. C. , Nozawa S. , Watanabe S. , Yoshida N.
Published: April 2005

Abstract. We have determined the MLT distribution and KP dependence of the ion upflow and downflow of the thermal bulk oxygen ion population based on a data analysis using the EISCAT VHF radar CP-7 data obtained at Tromsø during the period between 1990 and 1996: (1) both ion upflow and downflow events can be observed at any local time (MLT), irrespective of dayside and nightside, and under any magnetic disturbance level, irrespective of quiet and disturbed levels; (2) these upflow and downflow events are more frequently observed in the nightside than in the dayside; (3) the upflow events are more frequently observed than the downflow events at any local time except midnight and at any KP level and the difference of the occurrence frequencies between the upflow and downflow events is smaller around midnight; and (4) the occurrence frequencies of both the ion upflow and downflow events appear to increase with increasing KP level, while the occurrence frequency of the downflow appears to stop increasing at some KP level.Key words: Ionosphere (particle acceleration; plasma waves and instabilities) - Space plasma physics (transport processes)
Plasma density over Svalbard during the ISBJØRN campaign
Authors: Hall C. M. , van Eyken A. P. , Svenes K. R.
Published: April 2005

Abstract. In 1997, reliable operation of the EISCAT Svalbard Radar (ESR) was achieved and a rocket launching facility at Ny Ålesund on Svalbard (79°N, 12°E) (SVALRAK) was established. On 20 November, 1977, the first instrumented payload was launched from SVALRAK. Although the payload configuration had been flown many times previously from Andøya Rocket Range on the Norwegian mainland, this presented an unprecedented in situ determination of positive ion density over Svalbard. Simultaneously, ESR measured similar density profiles but in a higher altitude regime. We have combined the ESR measurements with ionosonde data to establish a calibration and subsequently combined the ground-based and in situ determined profiles to give a composite positive ion density profile from the mesosphere to the thermosphere.Key words: Ionosphere (polar ionosphere; instruments and techniques)
4D tropospheric tomography using GPS slant wet delays
Authors: Flores A. , Ruffini G. , Rius A.
Published: April 2005

Abstract. Tomographic techniques are successfully applied to obtain 4D images of the tropospheric refractivity in a local dense network of global positioning system (GPS) receivers. We show here how GPS data are processed to obtain the tropospheric slant wet delays and discuss the validity of the processing. These slant wet delays are the observables in the tomographic processing. We then discuss the inverse problem in 4D tropospheric tomography making extensive use of simulations to test the system and define the resolution and the impact of noise. Finally, we use data from the Kilauea network in Hawaii for February 1, 1997, and a local 4×4×40 voxel grid on a region of 400 km2 and 15 km in height to produce the corresponding 4D wet refractivity fields, which are then validated using forecast analysis from the European Center for Medium Range Weather Forecast (ECMWF). We conclude that tomographic techniques can be used to monitor the troposphere in time and space.Key words: Radio science (remote sensing; instruments and techniques)
Letter to the editor: Electric field fluctuations (25-35 min) in the midnight dip equatorial ionosphere
Authors: Hanumath Sastri J. , Luhr H. , Tachihara H. , Kitamura T. -I. , Rao J. V. S. V.
Published: April 2005

Abstract. Measurements with a HF Doppler sounder at Kodaikanal (10.2°N, 77.5°E, geomagnetic latitude 0.8°N) showed conspicuous quasi-periodic fluctuations (period 25-35 min) in F region vertical plasma drift, Vz in the interval 0047-0210 IST on the night of 23/24 December, 1991 (Ap = 14, Kp < 4-). The fluctuations in F region vertical drift are found to be coherent with variations in Bz (north-south) component of interplanetary magnetic field (IMF), in geomagnetic H/X components at high-mid latitude locations both in the sunlit and dark hemispheres and near the dayside dip equator, suggestive of DP2 origin. But the polarity of the electric field fluctuations at the midnight dip equator (eastward) is the same as the dayside equator inferred from magnetic variations, contrary to what is expected of equatorial DP2. The origin of the coherent occurrence of equatorial electric field fluctuations in the DP2 range of the same sign in the day and night hemispheres is unclear and merits further investigations.Key words: Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere-magnetosphere interactions)
Cross-field gradients: general concept, importance of multi-spacecraft measurements and study at 1 AU of the source intensity gradient for E > 30 keV solar event electrons
Authors: Chaizy P. A.
Published: April 2005

Abstract. Three main physical processes (and associated properties) are currently used to describe the flux and anisotropy time profiles of solar energetic par- ticle events, called SEP profiles. They are (1) the particle scattering (due to magnetic waves), (2) the particle focusing (due to the decrease of the amplitude of the interplanetary magnetic field (IMF) with the radial distance to the Sun) and (3) the finite injection profile at the source. If their features change from one field line to another, i.e. if there is a cross IMF gradient (CFG), then the shape of the SEP profiles will depend, at onset time, on the relative position of the spacecraft to the IMF and might vary significantly on small distance scale (e.g. 106 km). One type of CFG is studied here. It is called intensity CFG and considers variations, at the solar surface, only of the intensity of the event. It is shown here that drops of about two orders of magnitude over distances of ~104 km at the Sun (1° of angular distance) can influence dramatically the SEP profiles at 1 AU. This CFG can lead to either an under or overestimation of both the parallel mean free path and of the injection parameters by factor up to, at least, ~2-3 and 18, respectively. Multi-spacecraft analysis can be used to identify CFG. Three basic requirements are proposed to identify, from the observation, the type of the CFG being measured.Key words: Solar physics, astrophysics, and astronomy (energetic particles; flares and mass ejections) - Space plasma physics (transport processes)
Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind
Authors: Portnyagin Y. I. , Solovjova T. V.
Published: April 2005

Abstract. An updated empirical climatic zonally averaged prevailing wind model for the upper mesosphere/lower thermosphere (70-110 km), extending from 80°N to 80°S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude contour plots of monthly mean zonal and meridional winds for all months of the year, and of annual mean wind, amplitudes and phases of annual and semiannual harmonics of wind variations are analyzed to reveal the main features of the seasonal variation of the global wind structures in the Northern and Southern Hemispheres. Some results of comparison between the ground-based wind models and the space-based models are presented. It is shown that, with the exception of annual mean systematic bias between the zonal winds provided by the ground-based and space-based models, a good agreement between the models is observed. The possible origin of this bias is discussed.Key words: Meteorology and Atmospheric dynamics (general circulation; middle atmosphere dynamics; thermospheric dynamics)
Wavelet analysis on transient behaviour of tidal amplitude fluctuations observed by meteor radar in the lower thermosphere above Bulgaria
Authors: Pancheva D. , Mukhtarov P.
Published: April 2005

Abstract. On the basis of bispectral analysis applied to the hourly data set of neutral wind measured by meteor radar in the MLT region above Bulgaria it was demonstrated that nonlinear processes are frequently and regularly acting in the mesopause region. They contribute significantly to the short-term tidal variability and are apparently responsible for the observed complicated behavior of the tidal characteristics. A Morlet wavelet transform is proposed as a technique for studying nonstationary signals. By simulated data it was revealed that the Morlet wavelet transform is especially convenient for analyzing signals with: (1) a wide range of dominant frequencies which are localized in different time intervals; (2) amplitude and frequency modulated spectral components, and (3) singular, wave-like events, observed in the neutral wind of the MLT region and connected mainly with large-scale disturbances propagated from below. By applying a Morlet wavelet transform to the hourly values of the amplitudes of diurnal and semidiurnal tides the basic oscillations with periods of planetary waves (1.5-20 days), as well as their development in time, are obtained. A cross-wavelet analysis is used to clarify the relation between the tidal and mean neutral wind variability. The results of bispectral analysis indicate which planetary waves participated in the nonlinear coupling with the atmospheric tides, while the results of cross-wavelet analysis outline their time intervals if these interactions are local.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides) - Radio science (nonlinear phenomena)
IMPACT: an implicit time integration scheme for chemical species and families
Authors: Carver G. D. , Stott P. A.
Published: April 2005

Abstract. The implicit time integration scheme of Stott and Harwood (1993) was proposed as an efficient scheme for use in three-dimensional chemical models of the atmosphere. The scheme was designed for chemistry schemes using `chemical families', in which species with short lifetimes are grouped into longer-lived families. Further study with more complex chemistry, more species and reactions showed the scheme to be non-convergent and unstable under certain conditions; particularly for the perturbed chemical scenarios of polar stratospheric winters. In this work the scheme has been improved by revising the treatment of families and the convergence properties of the scheme. The new scheme has been named IMPACT (IMPlicit Algorithm for Chemical Time-stepping). It remains easy to implement and produces simulations that compare well with integrations using more accurate higher order schemes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry; lioposphere - composition and chemistry; instruments and techniques)
The WELSONS experiment: overview and presentation of first results on the surface atmospheric boundary-layer in semiarid Spain
Authors: Frangi J.-P. , Richard D. C.
Published: April 2005

Abstract. This study presents the preliminary results of the local energy budget and dynamic characteristics of the surface atmospheric boundary-layer (SBL) during the WELSONS (wind erosion and losses of soil nutrients in semiarid Spain) experiment. Some Mediterranean regions suffer land degradation by wind erosion as a consequence of their particular soil and climate conditions and inappropriate agricultural practice. In Spain, where land degradation by water erosion is well known, the lack of field studies to quantify soils losses by wind erosion resulted in the European Community organizing a scientific program for this specific issue. The European programme known as WELSONS was devoted to study the wind erosion process in central Aragon (NE Spain). This multidisciplinary experiment, which began in 1996 and finished in 1998, was carried out over an agricultural soil which was left fallow. Within the experimental field, two plots were delimited where two tillage treatments were applied, a mould-board ploughing (or conventional tillage denoted CT) and chisel ploughing (reduced tillage denoted RT). This was to study on bare soil the influence of tillage method on surface conditions, saltation flux, vertical dust flux, erosion rates, dynamics characteristics such as friction velocity, roughness length, etc., and energy budget. The partitioning of the available energy, resulting from the dynamics of the SBL, are quite different over the two plots because of their own peculiar soil and surface properties. The first results show that the RT treatment seems to provide a wind erosion protection. Because of the long data recording time and particular phenomena (formation of a crust at the soil surface, very dry conditions, high wind speed for instance), these microclimatological data acquired during the WELSONS programmes may be helpful to test atmospheric boundary-layer models coupled with soil models.Key words: Hydrology (desertification) - Meterology and atmospheric dynamics (general)
Magnetospheric lion roars
Authors: Baumjohann W. , Georgescu E. , Fornacon K.-H. , Auster H. U. , Treumann R. A. , Haerendel G.
Published: April 2005

Abstract. The Equator-S magnetometer is very sensitive and has a sampling rate normally of 128 Hz. The high sampling rate for the first time allows detection of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dawnside magnetosphere. The characteristics of these waves are virtually identical to the lion roars typically seen at the bottom of the magnetic troughs of magnetosheath mirror waves. The magnetospheric lion roars are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.2 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is nearly always smaller than 1°.Key words: Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and instabilities; plasma waves and instabilities)
A survey of magnetopause FTEs and associated flow bursts in the polar ionosphere
Authors: Neudegg D. A. , Cowley S. W. H. , Milan S. E. , Yeoman T. K. , Lester M. , Provan G. , Haerendel G. , Baumjohann W. , Nikutowski B. , Büchner J. , Auster U. , Fornacon K.-H. , Georgescu E.
Published: April 2005

Abstract. Using the Equator-S spacecraft and SuperDARN HF radars an extensive survey of bursty reconnection at the magnetopause and associated flows in the polar ionosphere has been conducted. Flux transfer event (FTE) signatures were identified in the Equator-S magnetometer data during periods of magnetopause contact in January and February 1998. Assuming the effects of the FTEs propagate to the polar ionosphere as geomagnetic field-aligned-currents and associated Alfvén-waves, appropriate field mappings to the fields-of-view of SuperDARN radars were performed. The radars observed discrete ionospheric flow channel events (FCEs) of the type previously assumed to be related to pulse reconnection. Such FCEs were associated with \\sim80% of the FTEs and the two signatures are shown to be statistically associated with greater than 99% confidence. Exemplary case studies highlight the nature of the ionospheric flows and their relation to the high latitude convection pattern, the association methodology, and the problems caused by instrument limitations.Key words: Ionosphere (polar ionosphere) · Magnetospheric physics (magnetosphere-ionosphere interaction; solar wind-magnetosphere interactions)
Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field
Authors: Milan S. E. , Lester M. , Cowley S. W. H. , Brittnacher M.
Published: April 2005

Abstract. We investigate the dayside auroral dynamics and ionospheric convection during an interval when the interplanetary magnetic field (IMF) had predominantly a positive Bz component (northward IMF) but varying By. Polar UVI observations of the Northern Hemisphere auroral emission indicate the existence of a region of luminosity near local noon at latitudes poleward of the dayside auroral oval, which we interpret as the ionospheric footprint of a high-latitude reconnection site. The large field-of-view afforded by the satellite-borne imager allows an unprecedented determination of the dynamics of this region, which has not previously been possible with ground-based observations. The location of the emission in latitude and magnetic local time varies in response to changes in the orientation of the IMF; the cusp MLT and the IMF By component are especially well correlated, the emission being located in the pre- or post-noon sectors for By < 0 nT or By > 0 nT, respectively. Simultaneous ground-based observations of the ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar. For an interval of IMF By \\approx 0 nT, these convection flow measurements suggest the presence of a clockwise-rotating lobe cell contained within the pre-noon dayside polar cap, with a flow reversal closely co-located with the high-latitude luminosity region. This pattern is largely consistent with recent theoretical predictions of the convection flow during northward IMF. We believe that this represents the first direct measurement of the convection flow at the imaged location of the footprint of the high-latitude reconnection site.Key words: Magnetospheric physics (auroral phenomena; magnetopause · cusp · and boundary layers; plasma convection)
A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar
Authors: McWilliams K. A. , Yeoman T. K. , Provan G.
Published: April 2005

Abstract. Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed ionospheric flow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic field lines, which occur during episodes of magnetic flux transfer to the terrestrial magnetosphere - flux transfer events or FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetary magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in different regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)
Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model
Authors: Namgaladze A. A. , Förster M. , Yurik R. Y.
Published: April 2005

Abstract. Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions.Key words: Atmospheric composition and structure (thermosphere · composition and chemistry) · Ionosphere (ionosphere · atmosphere interactions; modelling and forecasting)
Nonstationary pearl pulsations as a signature of magnetospheric disturbances
Authors: Feygin F. Z. , Kleimenova N. G. , Pokhotelov O. A. , Parrot M. , Prikner K. , Mursula K. , Kangas J. , Pikkarainen T.
Published: April 2005

Abstract. We analyse long-lasting (several hours) Pc1 pearl pulsations with decreasing, increasing or constant central frequencies. We show that nonstationary pearl events (those with either decreasing or increasing central frequency) are observed simultaneously with increasing auroral magnetic activity at the nightside magnetosphere while the stationary events (constant central frequency) correspond to quiet magnetic conditions. Events with decreasing central frequency are observed mostly in the late morning and daytime whereas events with increasing central frequency appear either early in the morning or in the afternoon. We explain the diurnal distribution of the nonstationary pearl pulsations in terms of proton drifts depending on magnetic activity, and evaluate the magnetospheric electric field based on the variation of the central frequency of pearl pulsations.Key words: Magnetospheric physics (magnetospheric configuration and dynamics; plasma waves and instabilities)