bluuebunny/crossref_metadata_2025 huggingface dataset:
Cassini Plasma Spectrometer Electron Spectrometer measurements during the Earth swing‐by on August 18, 1999
Authors: Rymer A. M. , Coates A. J. , Svenes K. , Abel G. A. , Linder D. R. , Narheim B. , Thomsen M. , Young D. T.
Published: January 2004

On August 18, 1999, Cassini flew by the Earth on its way to Saturn. The Cassini Earth swing‐by was the fastest traversal of the Earth's magnetosphere to date. The spacecraft was traveling at 9.1 RE hr−1 (16.1 km s−1) and made rapid traversals of several regions of the terrestrial magnetosphere. During the Cassini Earth swing‐by the Electron Spectrometer (ELS) collected almost 9 hours of data in the Earth's magnetosphere and almost 10 hours of solar wind data upstream of the Earth. During the pass, Cassini ELS sampled electrons in the solar wind, bow shock, magnetosheath, magnetopause, radiation belts, plasmasphere, plasma sheet, lobes, and crossings of the tail magnetopause. The purpose of this paper is (1) to give a summary of electron observations including the locations of magnetosphere boundary crossings and (2) to assess how the ELS is functioning as it takes measurements in the greatly differing plasma regimes encountered. Results are shown to be mainly consistent with previous observations with a few exceptions. In addition to anticipated results we present evidence of a low‐energy field‐aligned beam in the plasma sheet and evidence of asymmetry on the dayside and nightside plasmapause position. Preliminary calculations of density and temperature for the solar wind, magnetosheath, and plasma sheet are also presented.
The Io mass‐loading disk: Wave dispersion analysis
Authors: Blanco‐Cano X. , Russell C. T. , Strangeway R. J.
Published: January 2004

Ion cyclotron waves generated near Io have been detected by Galileo on December 7, 1995, October 11, 1999, November 26, 1999, and February 22, 2000. The waves are observed in the torus with frequencies near the gyrofrequencies of SO2+ and SO+ ions and propagate at angles up to 40° to the ambient magnetic field. The waves' properties are different on the four passes, and they change along each flyby, indicating that the torus composition is changing and that the spatial distribution of pickup ions is not uniform. While on December 1995 the waves had frequencies near the SO2+ gyrofrequency, on October 1999 and February 2000, spectra show peaks at the SO+ and the SO2+ gyrofrequencies. The SO+ waves had the largest amplitude almost all the time during these days. On November 1999 there are few data points, and the SO2+ waves had a larger amplitude than the SO+ waves. In some regions there are smaller‐amplitude waves with frequencies near the gyrofrequency of S+ ions, and on flyby 127 some waves had frequencies centered at the H2S+ gyrofrequency. We perform kinetic dispersion analysis to explain the origin of the observed waves. We find that SO2+ and SO+ ion cyclotron waves can be generated by ring‐beam distributions of pickup ions. The maximum growth occurs at parallel propagation, but growth at oblique angles is significant. The dominant mode depends on the composition of the pickup ions. The SO+ waves can be dominant if the density of the SO+ pickup ions is greater or equal to twice the density of the SO2+ ions. We present dispersion analysis for two cases; in the first one the SO2+ cyclotron mode is dominant in agreement with observations on December 7, 1995. In the second one the growth of SO+ waves is largest, resembling observations on October 11, 1999, and February 22, 2000. To explain the third peak observed in some spectra, we included a ring‐beam of S+ ions and find that the S+ cyclotron wave becomes unstable when the ring‐beam density is greater than or equal to 10% the density of the background S+ ions.
A substorm onset signature at the auroral zone as observed with SuperDARN and equatorial magnetometers
Authors: Saka O. , Kitamura T. , Tachihara H. , Shinohara M. , Trivedi N. B. , Sato N. , Ruohoniemi J. M. , Greenwald R. A.
Published: January 2004

Ionospheric convection enhancement with high westward velocities exceeding 1500 m s−1 was observed in association with the particle injection event by SuperDARN in the dusk sector of the auroral zone. Such a convection enhancement could be attributable to the enhanced sunward plasma flows in the dusk sector of the magnetosphere. At the dip equator a ground Pi2 onset was found to occur in association with these convection transients. The onset of the Pi2 lagged behind the convection enhancement by 4–11 min. It is argued that the convection transient could be the earliest indicator of the substorm onset among energetic particle injection, low‐latitude Pi2 onset, and, perhaps, the auroral breakup.
Interplanetary magnetic field By dependence of the relative position of the dayside ultraviolet auroral oval and the HF radar cusp
Authors: McWilliams K. A. , Milan S. E. , Yeoman T. K. , Sigwarth J. B. , Frank L. A. , Brittnacher M.
Published: January 2004

Comparative analyses of CUTLASS Super Dual Auroral Radar Network HF radar data and images of the dayside ultraviolet aurora from the Polar far ultraviolet imager and the Visible Imaging System Earth Camera have revealed that the GSM y component of the interplanetary magnetic field (By) affects the relative positions of ultraviolet auroral emissions and the HF radar signature of the cusp in the postnoon sector during episodes of flux transfer at the magnetopause. When By is positive, the region of strong auroral emissions is found to be at the same latitude as the radar footprint of the cusp. When By is negative, the radar cusp is found to be poleward of the strong auroral emissions. These results are consistent with models of the ionospheric convection and field‐aligned current response to reconnection at the magnetopause under positive and negative By conditions. We extend the models to predict the auroral and convection responses in the morning sector.
High‐resolution maps of the characteristic energy of precipitating auroral particles
Authors: Kosch M. J. , Honary F. , del Pozo C. F. , Marple S. R. , Hagfors T.
Published: January 2004

For the first time we produce high‐resolution maps of the characteristic energy of precipitating electrons from ground‐based instrumentation in the auroral zone over northern Scandinavia. This is done by combining intensity‐calibrated optical data at 557.7 nm from the Digital All‐Sky Imager (DASI) with auroral absorption images from the Imaging Riometer for Ionospheric Studies (IRIS). Energy maps are produced with high temporal (10 s) and spatial (10 km) resolution within a common geographic area of 240 × 240 km. Both IRIS and DASI have the European Incoherent Scatter (EISCAT) radar within their common field of view. EISCAT is capable of making accurate measurements of the electron density height profile which, with the assistance of an atmospheric model, are inverted into equivalent energy spectra of the flux of precipitating electrons. However, incoherent scatter radars generally have a very small field of view (<1°), making studies of the energy spectrum of the precipitating particles over a wide field of view impractical. Since IRIS and DASI are sensitive to high‐ and medium‐energy electrons, respectively, EISCAT data are used to calibrate the characteristic energy of the precipitating particles for an assumed energy spectrum against a combination of IRIS and DASI data. This empirical calibration is then used throughout the common field of view of IRIS and DASI. An initial study illustrates the spatial relationship between the different energy ranges during a substorm onset and illustrates a new way to interpret auroral phenomena.
Oblique “1‐Hz” whistler mode waves in an electron foreshock: The Cassini near‐Earth encounter
Authors: Tsurutani Bruce T. , Smith Edward J. , Burton Marcia E. , Arballo John K. , Galvan Carlos , Zhou Xiao‐Yan , Southwood David J. , Dougherty Michele K. , Glassmeier Karl‐Heinz , Neubauer Fritz M. , Chao Jih K.
Published: January 2004

The Cassini spacecraft flew toward the Earth in a trajectory almost along the Sun‐Earth line, giving a unique perspective of low‐frequency plasma waves in the Earth's foreshock. At the time of the fly‐through, the angle between the magnetic field and Sun‐Earth direction was ∼70°. For this orientation, only the most energetic (≥12 keV) ions could reach the upstream region, thus Cassini passed through an almost “pure” electron foreshock. We demonstrate the presence of nonlinear foreshock “1‐Hz” whistler‐mode waves and their properties. Power spectra demonstrate that the waves span a frequency range from ∼0.3 to ∼10 Hz with a center frequency of ∼2 Hz. Close to the bow shock the waves had peak‐to‐peak transverse amplitudes as large as ∼14 nT in a 35‐nT ambient field. The waves were compressive with a maximum value of Δ|B|/B0 ≈ 0.25. The waves were propagating primarily along B0. Of the waves, 82% were right‐hand‐polarized, 9% were linearly polarized, and 9% were left‐hand‐polarized (in the spacecraft frame). The wave amplitudes were largest near the bow shock and decreased with increasing distance in the upstream direction. Further from the shock the waves are determined to be propagating obliquely to B0 (θkB≥20°). There is an equal mix of right‐hand, left‐hand, and linearly polarized (in the spacecraft frame) waves. Left‐hand‐polarized waves propagating parallel to B0 were not detected. Wave power changed dramatically as the interplanetary magnetic field rotated slightly. Arguments are presented for why low‐energy (tens of eV) electrons are responsible for wave generation, rather than cyclotron resonant energetic (>13 keV) electrons.
ROCSAT 1 ionospheric plasma and electrodynamics instrument observations of equatorial spread F: An early transitional scale result
Authors: Su S.‐Y. , Yeh H. C. , Heelis R. A.
Published: January 2004

Ion density and vertical ion drift velocity sampled at 1024 Hz from the ROCSAT 1 satellite are used to examine the behavior of horizontal structures in equatorial spread F near 600 km altitude. An initial investigation shows that at scale sizes less than 100 m the relationships between the vertical drift and density structure are distinguished by the bulk plasma flow in the structure and by the background gradient in the density. Two adjacent equatorial bubble structures are examined: one in which the bulk plasma flow is upward and characteristic of an active evolving bubble and the other in which the bulk plasma flow is small and characteristic of a stagnated structure. We find that at scale sizes less than 100 m the velocity structure has a spectral slope that is consistently shallower than that of the density structure in the stagnated bubble but matches closely the spectrum of the density structure in the active bubble. Each of the bubble regions examined are characterized by one edge that has a much larger background gradient than the other. We find that in these bubbles, observed near 600‐km altitude, the lower background gradient is characterized by enhanced structure at 1‐km scale sizes.
Magnetometer measurements from the Cassini Earth swing‐by
Authors: Southwood D. J. , Dougherty M. K. , Balogh A. , Cowley S. W. H. , Smith E. J. , Tsurutani B. T. , Russell C. T. , Siscoe G. L. , Erdos G. , Glassmeier K‐H. , Gleim F. , Neubauer F. M.
Published: January 2004

Magnetometer data recorded by the Cassini spacecraft during the spacecraft's Earth swing‐by maneuver in August 1999 are discussed. The primary purpose of this paper is to show the instrument's performance in detection of magnetic phenomena in a planetary environment. Companion papers put the data in a broader geophysical context. The low noise and high time resolution of the instrument coupled with the unusual orbit did produce new information about old phenomena (e.g., a whistler‐like signal inside the near‐subsolar magnetopause, lower hybrid noise in the current sheets around a magnetosheath field null, and sharp changes in the ion cyclotron wave spectrum between the boundary layer and magnetosphere proper). The detection of irregular isolated 1–2 s duration small‐amplitude field strength dips in the vicinity of the nightside plasma trough appear to constitute a new discovery, tentatively identified as being evidence of plasmasphere interchange instability during a lull in background convection. The absolute scalar element of the instrument worked to plan, operating within 4 RE of Earth in parallel with the fluxgate sensors. In all respects, instrument performance bodes well for the Saturn orbital phase of the mission.
Scalar helium magnetometer observations at Cassini Earth swing‐by
Authors: Smith Edward J. , Dougherty Michele K. , Russell Christopher T. , Southwood David J.
Published: January 2004

When the Cassini spacecraft passed by Earth en route to the outer solar system, the magnetic field magnitude was measured with extremely high accuracy by the onboard helium magnetometer operating in the scalar mode. Magnitude measurements of the near‐equatorial field were obtained inbound from 4 to 1.17 RE at local times from postnoon to dusk and outbound to 4 RE between dusk and midnight. The observed field consisted of both the internally generated field of Earth and the field of external magnetospheric currents which were enhanced because of an ongoing magnetic storm. The contribution of the internal field was removed using a current version of the International Geomagnetic Reference Field (IGRF). An excellent characterization of the disturbance field was then obtained as a function of radial distance and local time. The observations were compared with available models of the disturbance field. Reasonable agreement was obtained, but discrepancies were found that were large enough to require changes in some of the model parameters. After removing the disturbance field, accuracy of measurement of high‐degree spherical harmonic moments of a planetary field, an important objective at Saturn, was investigated. The contribution of the sum of high‐degree moments to the Earth's field magnitude was obtained from the IGRF. The corresponding contribution to the measured field magnitude was derived using a theorem developed for that purpose. A close correspondence between the Cassini measurements and the IGRF was then found. The physics underlying the scalar measurements and the implementation of this mode in the Cassini magnetometer, the first time on a planetary mission, are described.
Support vector machine as an efficient tool for high‐dimensional data processing: Application to substorm forecasting
Authors: Gavrishchaka Valeriy V. , Ganguli Supriya B.
Published: January 2004

The support vector machine (SVM) has been used to model solar wind‐driven geomagnetic substorm activity characterized by the auroral electrojet (AE) index. The focus of the present study, which is the first application of the SVM to space physics problems, is reliable prediction of large‐amplitude substorm events from solar wind and interplanetary magnetic field data. This forecasting problem is important for many practical applications as well as for further understanding of the overall substorm dynamics. SVM has been trained on symbolically encoded AE index time series to perform supercritical/subcritical classification with respect to an application‐dependent threshold. It is shown that SVM performance can be comparable to or even superior to that of the neural networks model. The advantages of the SVM‐based techniques are expected to be much more pronounced in future space weather forecasting models, which will incorporate many types of high‐dimensional, multiscale input data once real time availability of this information becomes technologically feasible.
Cusp and magnetopause locations in global MHD simulation
Authors: Palmroth M. , Janhunen P. , Pulkkinen T. I. , Peterson W. K.
Published: January 2004

We use the global MHD code Grand Unified Magnetosphere Ionosphere Coupling Simulation (GUMICS‐4) to simulate the location and motion of the magnetospheric cusp and the subsolar magnetopause under various interplanetary magnetic field (IMF) directions and solar wind dynamic pressures. We identify the cusp in the simulation from the location of the open/closed field line boundary (OC boundary, equatorward edge of the cusp), determined by direct field line tracing, and several MHD parameters that are expected to react to the entry of the magnetosheath fluid. These parameters include the location of the maximum internal energy density and maximum diamagnetic depression and are collectively called the plasma proxies of the cusp. The simulation results show that with increasingly southward IMF the OC boundary and the plasma proxies move equatorward, as expected. During northward IMF, however, the plasma proxies are located equatorward of the OC boundary and thus on closed field lines. The GUMICS‐4 OC boundary location and the statistical plasma cusp location from Polar satellite observations are in good quantitative agreement during southward IMF, but during northward IMF the observed cusp is again several degrees equatorward from the simulated OC boundary. Therefore we conclude that during northward IMF the cusp identification from either the OC boundary or the plasma proxies may become problematic in MHD simulations and discuss the possible physical reasons. The simulation results further indicate that increasing solar wind dynamic pressure shifts the high‐altitude cusp slightly equatorward. Furthermore, the increasing pressure also pushes the magnetopause clearly earthward, as expected, while the same field line in the ionosphere shifts only slightly equatorward, implying changes in the field line shape as the pressure changes. In other respects, the simulated magnetopause is in quantitative agreement with the empirical model of Shue et al. [1998].
Properties of lower hybrid solitary structures: A comparison between space observations, a laboratory experiment, and the cold homogeneous plasma dispersion relation
Authors: Schuck P. W. , Bonnell J. W. , Pinçon J.‐L.
Published: January 2004

Lower hybrid solitary structures have been observed by sounding rockets in the auroral ionosphere for over a decade and a half. Surprisingly, few laboratory experiments have attempted to reproduce this interesting phenomena. Recently, Rosenberg and Gekelman [2001] investigated the interaction between fluctuations near the lower hybrid resonance and field‐aligned density striations using the Large Plasma Device at the University of California, Los Angeles. The laboratory measurements of electromagnetic fluctuations localized in a plasma density gradient are new and interesting. This experiment represents another in a series of laboratory investigations that use predictions of the cold homogeneous plasma dispersion to interpret observations of lower hybrid fluctuations interacting with a zero‐order plasma density gradient [Bamber et al., 1994, 1995; Rosenberg and Gekelman, 1998]. This experiment is also the first attempt to directly compare laboratory phase velocity estimates with interferometric electric field measurements of lower hybrid solitary structures by the AMICIST, TOPAZ III and PHAZE II sounding rockets [Pinçon et al., 1997; Schuck et al., 1998; Bonnell et al., 1998]. This paper compares the laboratory and space measurements and concludes that they represent completely different phenomena. Furthermore, significant discrepancies between the predictions of the cold homogeneous plasma dispersion relation and the laboratory observations are presented. We speculate that these discrepancies arise because plasma density gradients, essential to description of the laboratory experiment, are neglected in the cold homogeneous plasma dispersion relation.
Comment on “Properties of lower hybrid solitary structures: A comparison between space observations, a laboratory experiment, and the cold homogeneous plasma dispersion relation” by Schuck et al.
Authors: Gekelman Walter
Published: January 2004

Laboratory experiments involving the interaction of lower hybrid waves and density cavities with full width at half maximums ranging from 1 ≅ κ⟂δ ≤ 4, where δ = is the collisionless skin depth, were performed several years ago at the University of California, Los Angeles. The results were published in the Journal of Geophysical Research in December 2001 [Rosenberg and Gekelman, 2001]. These experiments are relevant to scaled parameters in the auroral ionosphere. This is a comment to the paper of Schuck et al. [2003], regarding the laboratory experiment on lower hybrid (LH) waves in the presence of a density striation. The main point Schuck et al. [2003] wish to make is that density striations in the auroral ionosphere are narrower than δ and that κ⟂δ ≈ 10 there. They argue that if this condition is not strictly satisfied in laboratory experiment then they are inappropriate to model the physics occurring in the ionosphere. In our experiments an incoming short perpendicular wavelength lower hybrid wave impinges upon a density striation which is many parallel (to B0) LH wavelengths long. A striking transformation occurs in which a cavity mode confined to the density gradient of the striation is excited. The mode localization does not depend on the ratio of the cavity diameter with respect to δ. We discuss the properties of lower hybrid waves, the experimental results as well as differences in the rocket and laboratory experiments.
Assimilation of global‐scale and mesoscale electric fields from low‐latitude satellites
Authors: Eccles J. Vincent
Published: January 2004

Equatorial satellites can measure key drivers of the low‐latitude ionosphere globally and frequently. The electric field and plasma drift instruments of the Communications and Navigation Outage System satellite will provide redundant observations of the most important driver of low‐latitude ionosphere structure, that is, the zonal electric field and resulting E × B plasma drift. The electric field data from the San Marco D satellite have been reduced to E × B plasma drift equivalents and are used to, first, examine data ingestion into an ionosphere model for weather sensitive specifications of the ionosphere and, second, explore use of the mesoscale (<1000 km) features in the E × B plasma drift to forecast the spatial mapping of signal scintillation associated with equatorial spread F in the postsunset ionosphere. The ingestion of the global‐scale, satellite‐based plasma drift observations into an ionosphere model improves electron density specifications over climatology when results are compared with the satellite in situ electron density measurements. Examination of the presunset and postsunset passes of the San Marco D satellite over a specific longitude sector suggests that the mesoscale structure in the zonal electric field can be used to predict the position and spacing of large plasma plumes associated with equatorial spread F in the postsunset ionosphere. A presunset forecast of the postsunset spatial location of plasma plumes can be used to spatially refine forecast maps of signal scintillation.
Quantifying the nitrous oxide source from coastal upwelling
Authors: Nevison Cynthia D. , Lueker Timothy J. , Weiss Ray F.
Published: January 2004

A continuous record of atmospheric N2O measured from a tower in northern California captures strong pulses of N2O released by coastal upwelling events. The atmospheric record offers a unique, observation‐based method for quantifying the coastal N2O source. A coastal upwelling model is developed and compared to the constraints imposed by the atmospheric record in the Pacific Northwest coastal region. The upwelling model is based on Ekman theory and driven by high‐resolution wind and SST data and by relationships between subsurface N2O and temperature. A simplified version of the upwelling model is extended to the world's major eastern boundary regions to estimate a total coastal upwelling source of ∼0.2 ± >70% Tg N2O‐N/yr. This flux represents ∼5% of the total ocean source, estimated here at ∼4 Tg N2O‐N/yr using traditional gas‐transfer methods, and is probably largely neglected in current N2O budgets.
N2O and CH4 variations during the last glacial epoch: Insight into global processes
Authors: Flückiger Jacqueline , Blunier Thomas , Stauffer Bernhard , Chappellaz Jérôme , Spahni Renato , Kawamura Kenji , Schwander Jakob , Stocker Thomas F. , Dahl‐Jensen Dorthe
Published: January 2004

Greenhouse gas measurements along polar ice cores provide important insight into the former composition of the atmosphere, its natural variations, and the responses to fast climatic changes in the past. We present high‐resolution nitrous oxide (N2O) and methane (CH4) records measured along two ice cores from central Greenland covering part of Marine Isotope Stages 3 and 4 in the last glacial epoch. The N2O data confirm the hypothesis that N2O shows variations in phase to fast climatic changes observed in the Northern Hemisphere, the so‐called Dansgaard‐Oeschger (D‐O) events. Variations exist not only for events with a long duration (1500 years and more) but also for the shorter ones. The comparison with CH4 unveils interesting differences between the response of CH4 and N2O to D‐O events. While the average amplitudes of CH4 oscillations associated with D‐O events are similar to those of the Northern Hemisphere summer insolation, the magnitude of the N2O concentration change instead correlates with the duration of the D‐O events. The records give further insight into the timing of concentration changes at the beginning of D‐O events. They show that for long‐lasting events the N2O concentration starts to increase before both the sharp increase in the CH4 concentration and the temperature reconstructed for Greenland.
First gaseous Sulfur (VI) measurements in the simulated internal flow of an aircraft gas turbine engine during project PartEmis
Authors: Katragkou E. , Wilhelm S. , Arnold F. , Wilson C.
Published: January 2004

Gaseous S(VI) (SO3 + H2SO4) has been measured by chemical ionization mass spectrometry (CIMS) in the simulated internal flow of an aircraft gas turbine in a test rig at ground level during the PartEmis 2002 campaign. Building on S(VI) and calculated total sulfur ST the abundance ratio ε = S(VI)/ST was determined. The measurements to be reported here were made at two sampling points, for two engine test conditions representative of old and modern aircraft cruise and for a fuel sulfur content FSC = 1270 ppm. For both cruise conditions the measured ε increased with increasing exhaust age from the high pressure to the low pressure stage. For each pressure stage ε was higher in the modern cruise condition. The maximum ε (2.3 ± 1.2%) was obtained for modern cruise and the low pressure stage. Our present data suggest that modern engines have a somewhat higher conversion efficiencies than old engines.
The effect on photochemical smog of converting the U.S. fleet of gasoline vehicles to modern diesel vehicles
Authors: Jacobson Mark Z. , Seinfeld John H. , Carmichael Greg R. , Streets David G.
Published: January 2004

With the increased use of particle traps and nitrogen oxide (NOx) control devices to reduce air pollution, “modern” diesel vehicles are being encouraged over gasoline vehicles globally as a central method of slowing global warming. Data to date, though, suggest that the NO2:NO ratio from modern diesel may exceed that of gasoline, and it is difficult to reduce diesel NOx below gasoline NOx without increasing particle emissions. Here, it is calculated that, unless the diesel NO2:NO ratio and total NOx are reduced to those of gasoline, modern diesel, which should have lower hydrocarbon (HC) and carbon monoxide (CO) emissions than gasoline, may still enhance photochemical smog at the surface and aloft, on average, over the U.S. relative to gasoline. The reason is that vehicle‐produced smog in the U.S. depends more on NOx and the NO2:NO ratio than on HCs or CO. It is also found that vehicle NOx controls may be more effective than NO2:NO ratio controls at reducing ozone.
Observation of sprites over the Sea of Japan and conditions for lightning‐induced sprites in winter
Authors: Hayakawa M. , Nakamura T. , Hobara Y. , Williams E.
Published: January 2004

We have succeeded in observing sprites for winter lightning in the Hokuriku area (Japan Sea side) of Japan in the winter of 2001/2002. The optical results on 3 days are compared with the corresponding characteristics of parent (causative) lightning with particular attention to the significant differences between Hokuriku winter lightning and the more widely studied continental lightning. Despite significant differences with Hokuriku winter lightning, we have found nearly the same sprite properties as already observed in the U.S. continent with a significant difference (simpler shape for Hokuriku winter sprite). Then, we have also discussed the criteria for sprite occurrence. Specifically, two similar criteria are found: (1) cloud‐to‐ground discharges of positive polarity and (2) the presence of a certain threshold in vertical charge moment (200–300 C km) (roughly consistent with that for the U.S. continent). Mesoscale convective systems are not necessary to store the charge necessary for sprites, but the parent Hokuriku winter clouds are substantially smaller than the minimum scale for sprite occurrence in the continental lightning; however, it is larger in area than ordinary summer thunderclouds. However, there may exit another condition such as clustering or self‐organizing effect of thunderclouds for sprite production.
Dynamics of charged particles in bifurcated current sheets: The κ ≈ 1 regime
Authors: Delcourt D. C. , Malova H. V. , Zelenyi L. M.
Published: January 2004

We examine the nonlinear dynamics of charged particles in the double‐hump current sheets that develop during the late growth phase of substorms. We focus on particles for which the adiabaticity parameter κ (defined as the square root of the minimum curvature radius to maximum Larmor radius ratio) is of the order of unity. We show that as in the case of a simple parabolic field reversal, the magnetic moment scattering experienced by these particles may be described as the result of perturbation of the gyromotion by an impulsive centrifugal force. Here however the double‐hump structure of the current sheet leads to two successive centrifugal perturbations, which has a significant impact on the net change of magnetic moment. In a single‐hump current sheet, three distinct regimes of magnetic moment variations are obtained for a given value of κ, namely, systematic enhancement at small pitch angles, negligible change at large pitch angles, and in between either damping or enhancement depending upon gyration phase. In contrast, in a double‐hump current sheet, repeated application of this three‐branch pattern can lead to magnetic moment damping for particles that previously experience magnetic moment enhancement and vice versa. The gyrophase gain both during and between the centrifugal impulses is found to play an essential role in the net magnetic moment change. In particular, in contrast to single‐hump current sheets, the κ ≈ 1 limit may be characterized by quasi‐adiabatic behavior with negligible variations of the magnetic moment.
Role of storm track activity in the interannual seesaw of summer precipitation over northern Eurasia
Authors: Fukutomi Yoshiki , Masuda Kooiti , Yasunari Tetsuzo
Published: January 2004

Oscillation between relatively dry and wet extremes is a noteworthy characteristic of the interannual variability in summer precipitation over Siberia. Recently, we identified an out‐of‐phase relationship in the temporal signature of basin‐scale precipitation between eastern and western Siberia (ES and WS). This east‐west seesaw has been especially pronounced during the past 30 years. The spatial structure of large‐scale precipitation and circulation anomalies associated with this east‐west seesaw is characterized by an east‐west dipole across northern Eurasia. We extended our work to investigate the important atmospheric processes involved in the dipole patterns of precipitation and large‐scale circulation anomalies for the northern summers (June–August) of 1972–2001. In particular, this work focuses on the role of storm track activities associated with synoptic‐scale (<10 days) eddies in producing the stationary waves that correspond to the precipitation anomaly dipoles. Linear regression and composite analyses of various eddy statistics are performed for two contrasting extremes in the Siberian summer precipitation seesaw. These two extreme phases are denoted ES‐wet‐WS‐dry and WS‐wet‐ES‐dry. The summer mean atmospheric anomalies related to the precipitation seesaw show stationary wavetrain patterns in conjunction with the precipitation dipole anomalies. The cold trough/warm ridge dipole corresponds to the relative wet and dry region. Analysis of storm track activity reveals similar east‐west contrasting structures, meaning that the displacements associated with the anomalous storm tracks are accompanied by a phase reversal between the two extreme phases. An anomalous stationary trough (ridge) corresponds to the anomalous high‐(low‐)synoptic‐scale‐eddy‐activity region in both ES and WS. The forcing by synoptic‐scale eddies is examined to confirm the storm track feedback on the Eurasian stationary waves. The results show that barotropic feedback induced by synoptic‐scale eddy vorticity fluxes is in phase with the Eurasian wave field. Cyclonic (anticyclonic) circulation forcing is collocated with the anomalous stationary trough (ridge). These spatially coherent relationships suggest that storm track feedback due to eddy vorticity fluxes helps to reinforce and maintain the Eurasian wave structure coupled with the precipitation dipole pattern of each phase. Consequently, the interannual variability of the Eurasian storm track intensity and location is a crucial factor in forcing the mean precipitation and circulation patterns between the two extreme phases.
Global patterns of marine nitrogen fixation and denitrification
Authors: Gruber Nicolas , Sarmiento Jorge L.
Published: January 2004

A new quasi‐conservative tracer N*, defined as a linear combination of nitrate and phosphate, is proposed to investigate the distribution of nitrogen fixation and denitrification in the world oceans. Spatial patterns of N* are determined in the different ocean basins using data from the Geochemical Ocean Sections Study (GEOSECS) cruises (1972–1978) and from eight additional cruises in the Atlantic Ocean. N* is low (< −3 µmol kg−1) in the Arabian Sea and in the eastern tropical North and South Pacific. This distribution is consistent with direct observations of water column denitrification in these oxygen minimum zones. Low N* concentrations in the Bering Sea and near the continental shelves of the east and west coasts of North America also indicate a sink of N* due to benthic denitrification. High concentrations of N* (>2.0 µmol kg−1) indicative of prevailing nitrogen fixation are found in the thermocline of the tropical and subtropical North Atlantic and in the Mediterranean. This suggests that on a global scale these basins are acting as sources of fixed nitrogen, while the Indian Ocean and parts of the Pacific Ocean are acting as sinks. Nitrogen fixation is estimated in the North Atlantic Ocean (10°N–50°N) using the N* distribution along isopycnal surfaces and information about the water age. We calculate a fixation rate of 28 Tg N yr−1 which is about 3 times larger than the most recent global estimate. Our result is in line, however, with some recent suggestions that pelagic nitrogen fixation may be seriously underestimated. The implied flux of 0.072 mol N m−2 yr−1 is sufficient to meet all the nitrogen requirement of the estimated net community production in the mixed layer during summer at the Bermuda Atlantic Time‐series Study (BATS) site in the northwestern Sargasso Sea. Extrapolation of our North Atlantic estimate to the global ocean suggests that the present‐day budget of nitrogen in the ocean may be in approximate balance.
Changes in pH in the eastern equatorial Pacific across stage 5–6 boundary based on boron isotopes in foraminifera
Authors: Sanyal A. , Hemming N. G. , Broecker W. S. , Hanson G. N.
Published: January 2004

Estimates of paleo‐pH for the eastern equatorial Pacific Ocean across the oxygen isotopic stage 5–6 boundary have been made based on the boron isotopic composition of planktonic (Orbulina universa) and benthic (mixed species) foraminifera from core V19‐28. The estimated deep ocean pH during the penultimate glacial period was about 0.3 ± 0.1 pH units higher compared to the modern deep ocean. This is consistent with previously estimated deep ocean pH changes across the stage l–2 boundary in the western equatorial Pacific and tropical Atlantic, thus arguing against the possibility that the benthic foraminifera analyzed to estimate deep ocean pH changes have been significantly affected by anomalous local environment and/or diagenesis. The estimated changes in the deep ocean carbonate chemistry require a decoupling (of several kilometers) between the saturation horizon and the lysocline during the glacial periods. Though such a decoupling could be achieved by enhanced respiration CO2 driven calcite dissolution in sediments during glacial periods, it lacks support from the calcite sedimentary records. The boron isotopic compositions of planktonic foraminifera, on the other hand, indicate no significant pH change in the eastern equatorial Pacific surface ocean during the glacial‐interglacial transition. This is inconsistent with an expected higher surface ocean pH during the glacial period due to lower atmospheric pCO2 and is also in contrast with the previously estimated boron isotope based glacial‐interglacial pH change of 0.2 ± 0.1 pH units in the western equatorial Pacific and tropical Atlantic. The lack of change in eastern equatorial Pacific surface ocean pH between glacial‐interglacial periods could be attributed to less nutrient utilization efficiency and/or enhanced calcite production during glacial periods. Such a decrease in nutrient utilization efficiency and/or increase in calcite production would lead to a greater disequilibrium between the pCO2 of eastern equatorial Pacific surface ocean and that of the atmosphere, making this part of the ocean a greater source of CO2 to the atmosphere during glacial periods compared to today.
Frequency of manic symptoms during a depressive episode and unipolar ‘depressive mixed state’ as bipolar spectrum
Authors: Sato T. , Bottlender R. , Schröter A. , Möller H.‐J.
Published: January 2004

Objective:  To report the frequency of intra‐episode manic symptoms in depressive episodes, and to evaluate unipolar depressive mixed state (DMS) as bipolar spectrum.

Method:  A total of 958 (863 unipolar, 25 bipolar II, and 70 bipolar I) depressive in‐patients were assessed in terms of manic symptoms at admission, and several clinical variables using standardized methods.

Results:  The frequency of manic symptoms (flight of idea, logorrhea, aggression, excessive social contact, increased drive, irritability, racing thoughts, and distractibility) was significantly higher in bipolar depressives than in unipolar depressives. Unipolar depressives with DMS – defined as having two or more manic symptoms – had more similarities to bipolar depressives than to other unipolar depressives in clinical variables such as onset age, family history of bipolar disorder, and possibly suicidality.

Conclusion:  Depressive mixed state is frequent, particular in bipolar depressives. Unipolar depressives with DMS may be better classified into bipolar spectrum.
Erotomania induced by venlafaxine: a case study
Authors: Adamou M. , Hale A. S.
Published: January 2004

Objective:  To describe a never previously reported case of erotomania induced by venlafaxine and highlight the effect of antidepressants on the dopaminergic system.

Method:  A case of erotomania is described.

Result:  Erotomania occurring in two separate occasions developed after treatment with high doses of venlafaxine. The episode remitted only after lowering the dose of the venlafaxine.

Conclusion:  Erotomania may occur with agents such as antidepressants. The dopamine neurotransmission of mood can provide further evidence for the development of newer classes of antidepressants.
Deep brain stimulation for treatment‐refractory obsessive‐compulsive disorder: psychopathological and neuropsychological outcome in three cases
Authors: Gabriëls L. , Cosyns P. , Nuttin B. , Demeulemeester H. , Gybels J.
Published: January 2004

Objective:  Investigation of deep brain stimulation (DBS) as a last‐resort treatment alternative to capsulotomy in treatment‐refractory obsessive‐compulsive disorder (OCD).

Method:  Prospective single‐case based design with evaluation of DBS impact on emotions, behaviour, personality traits and executive function in three patients with OCD.

Results:  Two patients experienced sustained improvement of OCD symptoms with DBS. Yale‐Brown Obsessive‐Compulsive Scale (Y‐BOCS) dropped 12 points and 23 points to baseline and Y‐BOCS self‐rating scale (Y‐BOCS‐SRS) and Profile of Mood States (POMS) for depression and tension decreased with increasing stimulation amplitude. Total Maladjustment Score on the Brief Psychiatric Rating Scale reduced with 44 and 59% to baseline. Reduction in psychopathology was sustained under continuous stimulation. No deleterious impact of DBS on neuropsychological testing or personality traits measured on a self‐rated personality inventory was detected.

Conclusion:  These preliminary findings demonstrate that DBS may have important therapeutic benefits on psychopathology in OCD. No harmful side‐effects were detected during follow‐up (33/33/39 months, respectively).
Brain glucose metabolic changes associated with neuropsychological improvements after 4 months of treatment in patients with obsessive–compulsive disorder
Authors: Kang D.‐H. , Kwon J. S. , Kim J.‐J. , Youn T. , Park H.‐J. , Kim M. S. , Lee D. S. , Lee M. C.
Published: January 2004

Objective:  The study was designed to elucidate regional brain metabolic changes according to a treatment and their relationship with neuropsychological performance changes in obsessive–compulsive disorder (OCD).

Method:  Cerebral glucose metabolic rates were repeatedly measured before and after treatment in 10 patients with OCD using [18F]‐2‐fluoro‐deoxyglucose positron emission tomography (PET). They were compared on a voxel‐basis, and the correlations were counted between the regional metabolic changes and the degree to improvement on the neuropsychological assessments.

Results:  After treatment, the patients showed significant (P < 0.005, two‐tailed) regional metabolic changes in multiple brain areas involving frontal–subcortical circuits and parietal–cerebellar networks. Especially, the metabolic changes of the putamen, the cerebellum, and the hippocampus were significantly correlated with the improvement of the immediate‐ and delayed‐recall scores of the Rey‐Osterrieth Complex Figure Test (RCFT).

Conclusion:  These results suggest a possibility that metabolic changes of frontal–subcortical and parietal–cerebellar circuit changes may underlie cognitive improvements in patients with OCD.
Targeted group antenatal prevention of postnatal depression: a review
Authors: Austin M.‐P.
Published: January 2004

Objective:  To review the efficacy of antenatal group interventions aimed at reducing postnatal depression (PND) in ‘at risk’ women.

Method:  Medline, Psyclit, HEALTHSTAR, EMBASE, Cochrane library, UK National Research Register and CINHAL searches were performed from 1960 to December 2001 focussing on randomized controlled trials (RCTs).

Results:  As statistical synthesis of the studies was not feasible, a qualitative review is provided. All five studies reviewed suffer from substantial limitations including small numbers; unrealistic effect sizes; large attrition rates; lack of a systematic approach in identifying those ‘at risk’ and thus clinically heterogenous samples. Three of the studies used unvalidated interventions that were educational or supportive in approach. While one such study reported a benefit of intervention, the largest study using a structured intervention, reported no effect. A very small study using interpersonal therapy, was promising but needs replication with an adequate sample size.

Conclusion:  There is currently little evidence from RCTs to support the implementation of antenatal group interventions to reduce PND in ‘at risk’ women. Further studies addressing the significant methodological limitations are recommended before concluding that antenatal targeted interventions have no place in maternity care.
Bisphenol A affects glucose transport in mouse 3T3‐F442A adipocytes
Authors: Sakurai Kenichi , Kawazuma Michiru , Adachi Tetsuya , Harigaya Toshio , Saito Yasushi , Hashimoto Naotake , Mori Chisato
Published: January 2004

Recently, environmental chemicals have appeared in daily human life, and these chemicals have been incidentally taken in by humans. The serum concentrations of some of these chemicals have been found to be associated with the onset and incidence rate of diabetes mellitus. It has been suggested that one of the environmental chemicals, bisphenol A (BPA), has hormone‐like activity. It has also been demonstrated that some hormones affect insulin resistance and fat distribution in the body. To study the effects of these environmental chemicals on glucose metabolism, the effect of BPA on glucose transport in mouse 3T3‐F442A adipocytes was investigated. The 3T3‐F442A adipocytes were incubated with various concentrations of BPA in a medium. Deoxyglucose uptake assay was performed with and without insulin. Immunoblot analysis was performed with a glucose transporter (GLUT) 4‐specific antibody and antiphosphotyrosine antibody. The BPA treatment enhanced basal and insulin‐stimulated glucose uptake, and caused an increased amount of GLUT4 protein. Thus, the enhanced glucose uptake resulting from the BPA treatment was at least partially due to the increased amount of GLUT4. Tyrosine phosphorylation of insulin receptor substrate‐1 with insulin stimulation was not significantly affected. In conclusion, it was demonstrated that BPA, one of the chemicals that we intake incidentally, affects the glucose transport in adipocytes, and also that the environmental chemicals may be identified as one of the environmental factors that affect diabetes and obesity.

British Journal of Pharmacology (2004) 141, 209–214. doi:10.1038/sj.bjp.0705520