bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon pools and accumulation in peatlands of the former Soviet Union
Authors: Botch M. S. , Kobak K. I. , Vinson T. S. , Kolchugina T. P.
Published: February 2004

To date, the areal extent, carbon pools, rate of carbon accumulation, and role of peatlands of the former Soviet Union (FSU) in the terrestrial carbon cycle has not been fully recognized. This is a consequence of the fact that many peatlands in the FSU, especially noncommercial peatlands, were never studied and properly mapped. An estimate of the areal extent, carbon pools, and rate of carbon accumulation in peatlands of the FSU obtained by interrelating a number of regional databases and maps, including formerly classified maps, is presented herein. Commercial peatlands were categorized by regional type which facilitated an evaluation of their age and quality. Noncommercial peatlands were evaluated from classified regional topographic maps. Air photographs were used to identify peatlands of northern landscapes. The total peatland area of the FSU was estimated at 165 Mha (106 hectares) which was two times greater than the most recent estimates based on thematic maps. The peat carbon pool was estimated at 215 Pg C. Half of this amount was in raised bogs. The rate of peat accumulation varied from 12 g C m−2 yr−1 (polygonal mires) to 72–80 g C m−2 yr−1 (fens and marshes). The total rate of carbon accumulation in FSU peatlands was 52 Tg C yr−1. Carbon emissions from peat utilization in the FSU were estimated at 122 Tg C yr−1. Thus, at present, peat accumulation/utilization in the FSU is a net source of approximately 70 Tg C yr−1 to the atmosphere.
Diurnal asymmetry of surface temperature trends over India
Authors: Kumar K. Rupa , Kumar K. Krishna , Pant G. B.
Published: February 2004

Diurnal asymmetry of the recent surface warming, reported for several continental areas, is believed to be related to changes in cloudiness, humidity, atmospheric circulation patterns, winds and soil moisture. This paper presents linear trend analyses of maximum and minimum temperature data at 121 stations in India during the period 1901–87. While the mean temperature trends over India are similar to the global and hemispheric trends, there are marked differences in their diurnal manifestation from those reported for other areas. The increase in the mean temperatures over India is almost solely contributed by the maximum temperatures, with the minimum temperatures remaining practically trendless, leading to an increase in the diurnal range of temperatures. These trends do not show any significant urban or altitude bias. There are some differences in the trends on smaller spatial and temporal scales, but the increase of maximum temperature is predominant over a major part of India, particularly in winter and post‐monsoon seasons.
Impact crater degradation on venusian plains
Authors: Izenberg Noam R. , Arvidson Raymond E. , Phillips Roger J.
Published: February 2004

In venusian plains, impact craters without extensive low backscatter ejecta deposits are more likely to have low backscatter floors, be embayed by volcanic deposits, and exhibit fractures as compared to craters with extensive low backscatter ejecta. We interpret these trends as evidence of ongoing degradation of low backscatter ejecta by aeolian activity, weathering, and volcanism. Using a crater age sequence based on extent of preservation of low backscatter ejecta, together with Monte Carlo simulations, we find that tectonic activity has extended over a longer time period than volcanism.
Characteristic time scale of auroral electrojet data
Authors: Takalo J. , Timonen J.
Published: February 2004

The structure function of the AE time series shows that the AE time series is self‐affine such that the scaling exponent changes at the time scale of approximately 113 (±9) minutes. Autocorrelation function is shown to have scaling properties similar to those of the structure function. From this result it can be deduced that the time scale at which the scaling properties of the AE data change should equal the typical autocorrelation time of these data. We find the typical autocorrelation time of the AE data is 118 (±9) minutes. The characteristic time scale of the AE data appears as a spectral break in their power spectrum at a period of about twice the autocorrelation time.
Role of the plasma acceleration time in the dynamics of the Jovian magnetosphere
Authors: Vasyliũnas Vytenis M.
Published: February 2004

The time needed to accelerate plasma in the Jovian magnetosphere to the self‐consistent flow imposed by coupling to the ionosphere is proportional to the Pedersen conductivity times the magnetic field divided by the flux tube content. Where this acceleration time becomes longer than the plasma outflow time, it is not possible to maintain magnetospheric plasma in corotation with the planet; comparison of the two time scales gives a general estimate of the limiting distance for corotation, identical to that previously derived by Hill from a specific flow model. At distances well beyond this limit, the magnetosphere becomes effectively decoupled from the ionosphere. In describing rotationally driven radial diffusion, inertial effects must be included whenever the acceleration time is not short compared to the eddy circulation time; they impose an upper bound on the circulation time proportional to the corotational period.
On intense diverging electric fields associated with black aurora
Authors: Marklund Göran , Blomberg Lars , Fälthammar Carl‐Gunne , Lindqvist Per‐Arne
Published: February 2004

Results are presented from the double‐probe electric field instrument on the Freja satellite with particular focus on the fine‐structured and dynamic plasma of the upper auroral ionosphere. The high‐resolution measurements show frequently occuring intense and irregular fine‐scale electric fields similar to those observed at higher altitudes by, for example, the S3‐3 and Viking satellites. Whereas the high‐altitude fields tend to be directly related to the auroral fine‐structure this is not always the case for the low‐altitude fields as illustrated by high‐resolution data of a pair of very intense (≈ 1 V/m), narrow electric field structures in the post‐midnight sector in the large‐scale downward field‐aligned current region. The structures are found to be associated with an excess of positive space charge (diverging electric fields), dropouts of precipitating electrons as well as depletions of thermal plasma, and significant wave activity. Combined with the scale‐size of the structures (≈ 1 km) and the spacing between them (≈ 5 km) these observations suggest that the intense electric fields are related to east‐west aligned vortex street structures of black aurora, similar to auroral curls but with opposite sense of rotation (clockwise seen antiparallel to B) and a total absence of auroral emissions. The detection of these structures was made possible by the relatively low inclination of the Freja orbit, which at times is almost tangential to the auroral oval. Thus, the Freja orbit provides a new perspective for studying many nightside auroral phenomena both at smaller scales (vortices) and at larger scales as exemplified by observations of north‐south oriented auroral structures caused by rotational arc distortions.
DE‐1 and COSMOS 1809 observations of lower hybrid waves excited by VLF whistler mode waves
Authors: Bell T. F. , Inan U. S. , Lauben D. , Sonwalkar V. S. , Helliwell R. A. , Sobolev Ya. P. , Chmyrev V. M. , Gonzalez S.
Published: February 2004

Past work demonstrates that strong lower hybrid (LH) waves can be excited by electromagnetic whistler mode waves throughout large regions of the topside ionosphere and magnetosphere. The effects of the excited LH waves upon the suprathermal ion population in the topside ionosphere and magnetosphere depend upon the distribution of LH wave amplitude with wavelength λ. The present work reports plasma wave data from the DE‐1 and COSMOS 1809 spacecraft which suggests that the excited LH wave spectrum has components for which λ ≤3.5 m when excitation occurs at a frequency roughly equal to the local lower hybrid resonance frequency. This wavelength limit is a factor of ∼3 below that reported in past work and suggests that the excited LH waves can interact with suprathermal H+ ions with energy ≤6 eV. This finding supports recent work concerning the heating of suprathermal ions above thunderstorm cells.
Possible nitric acid coating formation over Pinatubo aerosols inferred with a microphysical code: A case study during EASOE
Authors: Rizi V. , Redaelli G. , Verdecchia M. , Visconti G. , Stefanutti L. , Wolf J. P.
Published: February 2004

Lidar observations at Sodankylä (Finland) on January 9 and 11 1992, made as part of the European Arctic Stratospheric Ozone Experiment (EASOE), showed very different profiles of backscattering ratio. A prominent layer was seen between potential temperatures of 420 and 445K on January 9, which was nearly absent in the backscattering profile between these isentropic surfaces on the 11th. Examination of the trajectories of the airmasses reaching Sodankylä on these days lead us to suggest that the larger returns on January 9th could arise from the formation of a nitric acid coating on volcanic aerosols. Simulations using a microphysical model produce results consistent with this suggestion. We conclude that nitric acid condensation on January 9 can explain the measurements, but that independent information would be needed to quantify the characteristics of the aerosol substrate.
Spatial and temporal 26‐day SST variations in the equatorial Indian Ocean using wavelet analysis
Authors: Meyers Steven D. , O'Brien James J.
Published: February 2004

Two‐year sea‐surface temperature time series of satellite data at two sites in the equatorial Indian Ocean are examined for oscillations with periods 2–70 days. The wavelet transform of the signals reveals a changing wavelet spectrum between August 1987 and November 1987 in the 10–30 day range, while the same time period in 1988 shows a relatively fixed spectrum. At 3° latitude and 53°E the 1987 wavelet coefficients with scales 10–30 days have about twice the amplitude they have in 1988. At 3° latitude and 56°E the 1987 waves have roughly half the amplitude as the 1988 waves. Activity with wavelet spectral peaks at periods near 12 days often precede these waves.
Rupture extent of the 1938 Alaskan earthquake as inferred from tsunami waveforms
Authors: Johnson Jean M. , Satake Kenji
Published: February 2004

Using tsunami waveforms, we estimate the source parameters of the 10 November 1938 Alaskan earthquake. The earthquake ruptured a 300‐km‐long segment of the Alaskan arc, which corresponds to the aftershock area. The seismic moment is approximately 20×1020 Nm, or Mw=8.2, and the moment release was concentrated in the eastern end of the aftershock zone. The tsunami and seismic evidence strongly suggest that the 1938 earthquake did not rupture into the Shumagin Islands gap.
Elevation‐Corrected thermal inertia and derived particle size on Mars and implications for the Tharsis Montes
Authors: Bridges Nathan T.
Published: February 2004

One persistent difficulty associated with the interpretation of Martian thermal inertia and the derivation of particle size from it has been the degree to which atmospheric properties affect both the energy balance at the surface and the gas conductivity. Because both these factors vary with atmospheric pressure, derivation of thermal inertias and particle sizes must incorporate a correction for elevation. Here, by utilizing currently available thermal models and laboratory data, fine component thermal inertia has been combined with topography to compute particle size corrected for these elevation‐dependent effects. The corrected particle sizes at high elevations are as much as 2 orders of magnitude larger than the uncorrected values, with the Tharsis shield volcanoes generally having inferred sizes larger than dust, in contrast to previous interpretations of a thick dust cover. This large effective particle size may be a manifestation of the average conductivity produced by a mixture of dust and intervening bedrock outcrops smaller in size than those computed by Christensen [1986b]. In addition, the time‐variable albedo in the upper regions of these volcanoes argues against the presence of large dust deposits.
Photodissociation of O2 and H2O in the middle atmosphere: Comparison of numerical methods and impact on model O3 and OH
Authors: Siskind David E. , Minschwaner Kenneth , Eckman Richard S.
Published: February 2004

We have compared three photochemical diurnal models of O3 and OH in the upper stratosphere and mesosphere which use different techniques for calculating the absorption of solar ultraviolet radiation by the O2 Schumann‐Runge bands. One model uses a detailed line‐by‐line representation of the O2 cross section from 1750–2050 Å, while the two others use lower resolution, parameterized cross sections. Using the parameterized cross sections, the calculated O3 profiles for both day and night agree with those obtained from the line‐by‐line model to within 6%. This appears to eliminate inaccuracies in the parameterized O2 cross section as a major cause of previously reported model O3 deficits. A portion of the residual differences from the line‐by‐line model are attributed to inaccuracies in the calculated H2O photolysis rate. A parameterized H2O cross section is offered which improves the accuracy of this calculation.
The Blake Geomagnetic Polarity Episode recorded in Chinese loess
Authors: Zhu R. X. , Zhou L. P. , Laj C. , Mazaud A. , Ding Z. L.
Published: February 2004

A geomagnetic anomaly consisting of three clearly defined periods of reverse polarity separated by two short intervals of normal polarity has been documented in a loess section near Xining, western China. On the basis of previous studies of Chinese loess stratigraphy, we correlate this geomagnetic polarity episode with the Blake event. While more research is needed to improve our understanding of the exact process of remanence acquisition of loess deposits, this study shows that loess may provide records of fast geomagnetic events and lends further support to the global nature of the Blake geomagnetic event.
Model study of multiple polar cap arcs: Occurrence and spacing
Authors: Zhu L. , Sojka J. J. , Schunk R. W. , Crain D. J.
Published: February 2004

A new scenario for the formation of multiple polar cap arcs is proposed based on the results from a time‐dependent electrodynamic model of polar cap arcs developed by Zhu et al. [1993]. The results suggest that the appearance of multiple polar cap arcs may not be due to multiple structures in the magnetospheric source region, but instead, may primarily be determined by the coupled magnetosphere‐ionosphere system in which the ionosphere plays an active role. It was found that with the same magnetospheric driver, a strong ionospheric background convection and an ionospheric background Hall conductance in the range of from 0.5 to 1.5 mho favor the occurrence of multiple polar cap arcs. It was also found that the spacing between individual arcs is highly correlated with the ratio of the enhanced Hall and Pedersen conductances (i.e., the hardness of the primary magnetospheric precipitation), which is allowed to vary in the model runs. A harder precipitation causes a wider spacing. In the modelings, the spacing ranged from about 20 kilometers to about 60 kilometers when the precipitation hardness increased.
Detection of creep along the Philippine Fault: First results of geodetic measurements on Leyte Island, central Philippine
Authors: Duquesnoy Th. , Barrier E. , Kasser M. , Aurelio M. , Gaulon R. , Punongbayan R. S. , Rangin C.
Published: February 2004

Geodetic trilateration/GPS measurements were acquired from experiments conducted in 1991 and 1993 in the central part of the Philippine Fault on Leyte island. Displacement vectors deduced from two least squares adjustments indicate a mean slip rate of 26±10 mm/yr at an azimuth of about N130°E. These values are consistent with the tectonic and kinematic data. Our results indicate that the displacements are: (1) almost parallel to the Philippine Fault, and (2) related to creep along the fault, because no moderate seismic events occurred between the two observation epochs.
Variations of connected porosity and inferred permeability in a thermally cracked granite
Authors: Géraud Yves
Published: February 2004

Connected porosity volume and throat diameter were measured in granitic samples with different porosity structures heated from 20 to 700°C. Three types of microstructures are recognized from SEM analysis: (1) a crack network of transgranular cracks with few intersections (2) a pipe network of intragranular and intergranular tubes with high connectivity (3) a mixed stucture of transgranular cracks connected by intragranular tube structures. Calculations predict a decrease of permeability through crack and mixed networks between 50 and 400°C followed by a sharp increase at higher temperatures. The decrease in permeability is associated predominantly with the decrease in throat diameter, whereas the increase in both throat diameter and the porosity volume account for the temperature rise. Only small variations of the permeability are predicted for the pipe network.
Estimating primary and secondary production of HCHO in eastern North America based on gas phase measurements and principal component analysis
Authors: Li Shao‐Meng , Anlauf Kurt G. , Wiebe H. Allan , Bottenheim Jan W.
Published: February 2004

Based on atmospheric measurements of multiple species at Egbert, a rural site in Ontario, Canada, during summer 1988, the emission ratios of HCHO/CO and HCHO/ΣNOy for area sources and secondary production of HCHO have been estimated using a modified principal component analysis technique. The technique yields three principal components that represent a photochemically aged air mass, a diurnal cycle, and fresh area emissions. The area emission component has an emission ratio CO/ΣNOy = 9±3 and SO2/CO = 0.005±0.003, in agreement with NAPAP area emission data for the eastern US [Buhr et al., 1992]. The emission ratios of HCHO/CO and HCHO/ΣNOy in this component are 0.0056±0.0022 and 0.05±0.007, respectively. If these ratios are typical of eastern North American area emissions, the total primary HCHO emission for this region will be 8×109 moles HCHO annually based on the NAPAP CO emission inventories. Evidence of secondary HCHO production can be found in the photochemically aged component which has considerably higher HCHO/CO (0.016±0.004) and HCHO/ΣNOy (0.29±0.03) ratios than the emission ratios. It is estimated that for every 1 ppb NOx converted to NOy, 0.4 ppb HCHO are produced for the ratio (1−NOx/NOy)<0.6; after which the relative HCHO production rate becomes smaller. Using this relative rate, the maximum total HCHO production over the eastern North America is estimated to be 1.3×1011 moles year−1, or approximately 16 times that from primary emission.
Transient electric signals prior to rock failure under uniaxial compression
Authors: Hadjicontis V. , Mavromatou C.
Published: February 2004

Transient variations of the electric field are detected, prior to the failure of a rock sample which is subjected to uniaxial compression at a variable rate. These precursory electric signals are attributed to the stress induced polarization of the sample and seem to have a form similar to the so called Seismic Electric Signals (SES), which are detected in Greece by the VAN network, prior to earthquakes. The emitted electric signals seem to follow in form the variations of the first time derivative of the externally applied stress. A tentative model for the origin of these signals is also discussed.
Recent observations of the OI 8446 Å emission over Millstone Hill
Authors: Lancaster R. S. , Kerr R. B. , Ng K. , Noto J. , Franco M. , Solomon Stanley C.
Published: February 2004

Evening twilight spectra of the OI 8446 Å emission were obtained during May and June of 1993 using a single‐etalon, pressure scanning, Fabry‐Perot interferometer located in the Millstone Hill Optical Facility. The goals of this work are to positively identify the 8446 Å emission in the twilight airglow and to determine the intensity decay as a function of solar depression angle. Also, a study of the relative triplet line strengths is performed in hopes of establishing the importance of the primary excitation mechanisms (photoelectron impact or Bowen fluorescence) during the twilight period. Although absent in most of the data, a distinct auroral influence is also found to contribute considerably, on occasion, to the emission over Millstone Hill. The ratio of the combined 8446.26 Å and 8446.38 Å intensities to the 8446.76 Å intensity varies as 0.13±0.03 per degree of solar depression angle, indicating that secondary excitation mechanisms are becoming increasingly important as evening twilight progresses. Bowen fluorescence is not found to be the primary excitation mechanism at any time during twilight, contributing just a few Rayleighs at most. These observations are an important first step toward a better characterization of highly variable thermospheric oxygen concentrations through ground‐based measurements of the OI 8446 Å emission.
Effect of nonstoichiometry on the magnetic and electrical properties of synthetic single crystal Fe2.4Ti0.6O4
Authors: Wanamaker B. J. , Moskowitz Bruce M.
Published: February 2004

A single crystal of titanomagnetite Fe2.4Ti0.6O4 (TM60) was synthesized using the floating zone technique. The Curie temperature, saturation magnetization at 5 K, and thermopower were measured for several pieces of the crystal as grown and following high temperature annealing at different oxygen fugacities within the stability field of the TM60. The magnetic and electrical data indicate that long‐range ordering in TM60 is a function of nonstoichiometry with higher cation vacancy concentrations producing a more random cation distribution. This effect may explain the differences among cation distribution models for TM developed previously by other workers.
Observation of kinetic Alfvén waves by the FREJA spacecraft
Authors: Louarn P. , Wahlund J. E. , Chust T. , de Feraudy H. , Roux A. , Holback B. , Dovner P. O. , Eriksson A. I. , Holmgren G.
Published: February 2004

It is shown that the low‐frequency (from 1 to 20 Hz) auroral electromagnetic turbulence consists of two kinds of phenomena: (1) magnetic fluctuations due to quasi‐static currents and (2) strong electric spikes (larger than 100 mV/m) with associated magnetic (30 nT) and density (dn/n ≥ 30%) fluctuations. These spikes are interpreted as kinetic Alfvén waves. They have transverse scale of the order of the electron inertia length (1 km) and then, could dissipate via the generation of a parallel electric field by finite electron mass effects. Given their strong Poynting flux (10−3 to 10−2 W/m²), they likely significantly contribute to the auroral plasma energization.
The impact of comet Shoemaker‐Levy 9 on the Jovian magnetosphere
Authors: Herbert Floyd
Published: February 2004

By the time of the impact of comet P/Shoemaker‐Levy 9 with Jupiter, the freshly‐broken surfaces of the accompanying rubble will have been outgassing for about two years, and will have produced an expanding and co‐moving cloud of gas hundreds ofRJacross. Much of this gas, escaping from the cometary fragments at low (≤ 1 km/s) speed, will arrive in the Jovian magnetosphere contemporaneously with the comet and drift through the magnetosphere. This gas, as it is photoionized, will be picked up primarily in the outer magnetosphere and the resulting high‐energy ions should intensify magnetospheric processes, such as Io plasma torus and auroral emissions, that are thought to be powered by outer magnetospheric mass loading. If the composition of the comet is similar to that of P/Halley, the power available from mass loading should be comparable to that driving the aurora (1014W) and at least an order of magnitude larger than that exciting the plasma torus for several weeks or months. Measurement of these emissions during and after the cometary encounter may constrain the mechanisms for energization of magnetospheric charged particle populations and magnetospheric transport processes.
Thermoelasticity of CaSiO3 perovskite and implications for the lower mantle
Authors: Wang Yanbin , Weidner Donald J.
Published: February 2004

We report measurements on thermal expansion of CaSiO3 perovskite within the stability field and its room temperature volume‐pressure behavior, as well as in situ determination of the perovskite stability field. The phase boundary between CaSiO3 perovskite and the lower‐pressure phase assemblage Ca2SiO4 + CaSi2O5 was determined at temperatures between 1200 and 1600 K, using NaCl as the pressure standard. At 1590(20) K, the boundary is located at about 11.3(3) GPa with a positive slope, in close agreement with previous quench studies. At 300 K, the perovskite structure remains metastable at pressures ∼ 2 GPa, below which the sample transforms into an amorphous phase, with an anomalous volume decrease of the remaining perovskite. The volume data above 2 GPa are fit using a second‐order Birch‐Murnaghan equation of state, yielding V0 = 45.83 (7) Å3 and K0 = 280(23) GPa. Over a wide temperature range of 600–1600 K, the average thermal expansion of CaSiO3 perovskite is α = 2.69(8) and 2.56(8)×10−5 K−1 at 10.6 and 11.7 GPa, respectively, with little temperature dependence. These data are combined with results on MgSiO3 perovskite to examine constraints on lower mantle composition. The predicted density of CaSiO3 perovskite is similar to that of PREM and the bulk modulus similar to that of (Mg,Fe)SiO3 perovskite under lower mantle conditions. Thus, including CaSiO3 yields an Fe/(Mg+Fe) ratio of 0.12(1) and an (Mg+Fe+Ca)/Si ratio of 1.7(3) for the upper portion of the lower mantle.
Dynamic orbit determination using GPS measurements from TOPEX/POSEIDON
Authors: Schutz B. E. , Tapley B. D. , Abusali P. A. M. , Rim H. J.
Published: February 2004

The GPS data acquired by the TOPEX/POSEIDON (T/P) Demonstration Receiver (DR) have been used in a dynamic orbit determination, which was based on the description of the gravitational and nongravitational forces in the equations of motion. The GPS carrier phase data were processed in a double difference mode to remove clock errors, including the effects of Selective Availability. Simultaneous estimation of the T/P orbit and GPS orbits was performed using five 10‐day cycles in the interval between December (1992) and April (1993). The resulting T/P orbits have been compared with the orbits determined from Satellite Laser Ranging, the French one‐way Doppler tracking system, DORIS, and with the JPL reduced dynamic orbits obtained from the GPS/DR data. Using similar dynamic orbit determination strategies and force models with the GPS/DR to those used with SLR/DORIS, the radial component of the T/P orbit (based on JGM‐2) was found to agree to better than 30 mm (rms) and 35 mm with the JPL reduced dynamic orbit. An experimental gravity tuning was accomplished using four cycles of GPS/DR data. The resulting GPS/DR‐orbits, determined by the dynamic technique with the experimental gravity field, are in better agreement with the JPL reduced dynamic orbits in both the radial component (21–25 mm) and altimeter crossover residuals than the JGM‐2 orbits.
Ionospheric response to traveling convection twin vortices
Authors: Schunk R. W. , Zhu L. , Sojka J. J.
Published: February 2004

Traveling convection twin vortices have been observed for several years. At ionospheric altitudes, the twin vortices correspond to spatially localized, transient structures embedded in a large‐scale background convection pattern. The convection vortices are typically observed in the morning and evening regions. They are aligned predominantly in the east‐west direction and have a horizontal extent of from 500–1000 km. Associated with the twin vortices are enhanced electric fields, particle precipitation, and an upward/downward field‐aligned current pair. Once formed, the twin vortex structures propagate in the tailward direction at speeds of several km/s, but they weaken as they propagate and only last for about 10–20 minutes. Because these convection structures might have a significant effect on the localized ionosphere, the USU ionospheric model was used to calculate the response of the ionosphere to “representative” traveling convection twin vortices for a range of background conditions. The ionospheric response includes localized temperature enhancements, ion composition changes, non‐Maxwellian ion distributions, and plasma upwelling events. The response is transient and the magnitude of the response depends on the background ionospheric conditions and on the characteristics of the twin vortices.
Ulysses at 50° south: constant immersion in the high‐speed solar wind
Authors: Phillips J. L. , Balogh A. , Bame S. J. , Goldstein B. E. , Gosling J. T. , Hoeksema J. T. , McComas D. J. , Neugebauer M. , Sheeley N. R. , Wang Y.‐M.
Published: February 2004

We present speed observations from the Ulysses solar wind plasma experiment through 50° south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km s−1 range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefactions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing spacecraft latitude. Trends in prevailing speed with increasing latitude support previous findings. A decrease in peak speed southward of 40° latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes.
Strain accumulation north of Los Angeles, California, as a function of time, 1977–1992
Authors: Savage J. C. , Lisowski M.
Published: February 2004

No significant change in the rate of strain accumulation in a 40×120 km trilateration network spanning the San Gabriel mountains was observed from 1977.5 to 1991.8 despite an apparent increase in seismicity (ML > 4.5) beginning in late 1987 in the northern Los Angeles basin immediately to the south. The observed deformation (0.13±0.01 µstrain/yr right‐lateral shear across a vertical plane striking N63°W±1°) can be attributed to strain accumulation on the San Andreas fault (local strike N65°W). No significant accumulation of compression normal to the strike of the San Andreas fault was observed in the network as a whole.
On the determination of biases in satellite‐derived temperature profiles
Authors: Bhatt Praful P. , Remsberg Ellis E. , Schmidlin Francis J. , Gordley Larry L. , Burton John C.
Published: February 2004

Comparisons are presented between Nimbus 7 LIMS mapped temperatures and both Datasonde and sphere in situ rocketsonde temperature measurements. With this approach up to 666 LIMS/Datasonde pairs were obtained for various pressure levels to look for small biases in LIMS temperatures as a function of altitude, latitude and season. Between 10‐1 hPa LIMS and Datasonde agree everywhere to better than ±2 K with the exception of a warm bias of about 3 K at 2 hPa at high latitudes. However, LIMS is colder than the Datasonde by about 4 K at 0.4 hPa and by about 8‐10 K at 0.1 hPa. When compared with the more accurate sphere temperatures the bias at 0.1 hPa is reduced by nearly one‐half. These results indicate that the LIMS zonal mean constituent profiles are nearly free of temperature bias, except perhaps at 0.1 hPa.
Comparison of column abundances from three infrared spectrometers during AASE II
Authors: Traub W. A. , Jucks K. W. , Johnson D. G. , Coffey M. T. , Mankin W. G. , Toon G. C.
Published: February 2004

Three Fourier transform infrared (FTIR) spectrometers were on board the NASA DC‐8 during the second Airborne Arctic Stratospheric Expedition (AASE II) in 1992. Two FTIRs used solar absorption and one used thermal emission. We compare over 2000 measurements from these 3 FTIRs, on 12 DC‐8 flights, for closely coincident air masses and times, both inside and outside the polar vortex. In the majority of cases the offset biases are quite small, in the range 1–4%, and comparable to the absolute precisions expected. In most cases the rms scatter is in the range 4–11%; this scatter is unlikely to be geophysical, but rather is probably instrumental or analytical in origin.
The Geotail Mission
Authors: Nishida A.
Published: February 2004

In this introductory article to the GEOTAIL special section, spacecraft specifications, science instruments, data handling procedures, and the orbit in the first 1.5 year of the operation are briefly described.
SPADE H2O measurements and the seasonal cycle of stratospheric water vapor
Authors: Hintsa Eric J. , Weinstock Elliot M. , Dessler Andrew E. , Anderson James G. , Loewenstein Max , Podolske James R.
Published: February 2004

We present measurements of lower stratospheric water vapor obtained during the SPADE mission with a new high precision, fast response, Lyman‐alpha hygrometer. The H2O data show a distinct seasonal cycle. For air that recently entered the stratosphere, data collected during the fall show much more water vapor than data from the spring. Fast quasi‐horizontal mixing causes compact relationships between water and N2O to be established on relatively short time scales. The measurements are consistent with horizontal mixing times of a few months or less. Vertical mixing appears to cause the seasonal variations in water vapor to propagate up to levels corresponding to air that has been in the stratosphere approximately one year.
A filament of energetic particles near the high‐latitude dawn magnetopause
Authors: Lui A. T. Y. , Williams D. J. , McEntire R. W. , Christon S. P. , Jacquey C. , Angelopoulos V. , Yamamoto T. , Kokubun S. , Frank L. A. , Ackerson K. L. , Tsuruda K.
Published: February 2004

The Geotail satellite detected a filament of tailward‐streaming energetic particles spatially separated from the boundary layer of energetic particles at the high‐latitude dawn magnetopause at a downstream distance of ∼80 RE on October 27, 1992. During this event, the composition and charge states of energetic ions at energies above ∼10 keV show significant intermix of ions from solar wind and ionospheric sources. Detailed analysis leads to the deduction that the filament was moving southward towards the neutral sheet at an average speed of ∼80 km/s, implying an average duskward electric field of ∼1 mV/m. Its north‐south dimension was ∼1 RE and it was associated with an earthward‐directed field‐aligned current of ∼5 mA/m. The filament was separated from the energetic particle boundary layer straddling the magnetopause by ∼0.8 RE and was inferred to be detached from the boundary layer at a downstream distance beyond ∼70 RE in the distant tail.
Evidence that Jupiter is not the source of the 2‐3 kHz heliospheric radiation
Authors: Gurnett D. A. , Kurth W. S.
Published: February 2004

It has been suggested that continuum radiation from Jupiter could provide the source for the 2‐ to 3‐kHz radio emissions detected by Voyagers 1 and 2 in the outer heliosphere. By a fortuitous set of circumstances the Ulysses flyby of Jupiter in early 1992 provided an opportunity to compare the intensity of a strong, new heliospheric radio emission event with the intensity of continuum radiation from Jupiter. These comparisons show no evidence that Jupiter is the source of the heliospheric radio emissions.
The determination of interplanetary magnetic field polarities around sector boundaries using E > 2 keV electrons
Authors: Kahler S. , Lin R. P.
Published: February 2004

The determination of the polarities of interplanetary magnetic fields (whether the field direction is outward from or inward toward the sun) has been based on a comparison of observed field directions with the nominal Parker spiral angle. These polarities can be mapped back to the solar source field polarities. This technique fails when field directions deviate substantially from the Parker angle or when fields are substantially kinked. We introduce a simple new technique to determine the polarities of interplanetary fields using E > 2 keV interplanetary electrons which stream along field lines away from the sun. Those electrons usually show distinct unidirectional pitch‐angle anisotropies either parallel or anti‐parallel to the field. Since the electron flow direction is known to be outward from the sun, the anisotropies parallel to the field indicate outward‐pointing, positive‐polarity fields, and those anti‐parallel indicate inward‐pointing, negative‐polarity fields.

We use data from the UC Berkeley electron experiment on the ISEE‐3 spacecraft to compare the field polarities deduced from the electron data, Pe (outward or inward), with the polarities inferred from field directions, Pd, around two sector boundaries in 1979. We show examples of large (>100°) changes in azimuthal field direction Φ over short (<1 hr) time scales, some with and some without reversals in Pe. The latter cases indicate that such large directional changes can occur in unipolar structures. On the other hand, we found an example of a change in Pe during which the rotation in Φ was < 30°, indicating polarity changes in nearly unidirectional structures. The field directions are poor guides to the polarities in these cases.
Recovery of stratospheric ozone over the United States in the winter of 1993–1994
Authors: Hofmann D. J. , Oltmans S. J. , Harris J. M. , Lathrop J. A. , Koenig G. L. , Komhyr W. D. , Evans R. D. , Quincy D. M. , Deshler T. , Johnson B. J.
Published: February 2004

Total ozone levels, which were 10–15% below normal over the U.S. during the winter of 1992–1993, returned to levels slightly above normal during the winter of 1993–1994. Investigation of ozone vertical profiles indicates that in the region where severe depletion occurred in 1992–1993 (25% reductions at 12–22 km), ozone had returned to normal, while above this region, ozone was abnormally high. Thus total ozone was also high. Low ozone values in 1992–1993 were believed to be related to heterogeneous chemistry on the Pinatubo volcanic aerosol. This interpretation is strengthened by these observations since the particle surface area available for heterogeneous processes in the stratosphere diminished substantially at midlatitudes during 1993 and was not replenished by transport from the equatorial reservoir during the winter as had occurred during the previous winter. However, the observation of continued unusually high ozone above 24 km in winter suggests that this phenomenon, thought to also have been at least partially due to heterogeneous chemistry, is mainly related to dynamics. Unusually high total ozone levels in high northerly latitudes during the winter of 1993–1994 and especially in early February, associated with warm stratospheric temperatures during December and January, are probably the source of high ozone above 24 km in midlatitudes at this time.
Long‐period earthquakes in the Long Valley Caldera Region, eastern California
Authors: Pitt A. M. , Hill D. P.
Published: February 2004

Most earthquakes occurring near Long Valley caldera since the onset of recurring swarm activity in 1980 have the broad‐band signature typical of tectonic or volcano‐tectonic earthquakes with impulsive, high‐frequency P and S waves. With the Mammoth Mountain earthquake swarm in mid 1989, we began detecting occasional events with a marked deficiency in energy above 5 Hz, a feature typical of long‐period (LP) volcanic earthquakes. These events occur beneath the southwest flank of Mammoth Mountain at focal depths ranging from 10 to 28 km, distinctly deeper than the 2‐ to 10‐km depth range for tectonic earthquakes in the area. The LP events occur at intervals ranging from weeks to months. Individual occurrences typically consist of several events within 2 to 5 minutes where the largest event has never been first. Magnitudes range from 0.5 to 1.8. The mid‐crustal focal depths of the LP events are similar to occurrences at a number of areas with Holocene volcanism in Japan and the western United States. They may indicate the movement of magmatic fluids but do not necessarily indicate an imminent volcanic eruption.
Structure of the neutral sheet in the distant tail (x=−210 Re) in geomagnetically quiet times
Authors: Nishida A. , Yamamoto T. , Tsuruda K. , Hayakawa H. , Matsuoka A. , Kokubun S. , Nakamura M. , Maezawa K.
Published: February 2004

We have analyzed the magnetic and the electric field data of GEOTAIL obtained in the neutral sheet of the distant tail at |x| = 210 Ree when Kp was 0 or 1. In the distant neutral sheet, By is strongly dependent on IMF By and when averaged in each IMF sector By is much larger than Bz. The average Bz is a few times of 0.1 nT or less so that the precise value is critically dependent on the offset determination with an accuracy better than 0.1 nT. The drift velocity is directed anti‐earthward and 300 to 400 km/s. A modified cusp reconnection model is proposed in which the tail field lines that reconnect with IMF on the surface of the tail are not open but traverse the neutral sheet. Magnetic torque is transmitted from the reconnection site along these tail field lines and produce the IMF‐dependent By component in the neutral sheet.
Ionospheric currents correlated with geomagnetic induced currents; Freja magnetic field measurements and the Sunburst Monitor System
Authors: Zanetti L. J. , Potemra T. A. , Anderson B. J. , Erlandson R. E. , Holland D. B. , Acuña M. H. , Kappenman J. , Lesher R. , Feero B.
Published: February 2004

Temporal and spatial fluctuations of large‐scale electric currents totaling millions of amperes in the ionosphere have long been known to induce current and voltage in the Earth's surface and on large manmade conductive structures. A strong, persistent solar wind can interact with the geomagnetic environment and produce auroral zone currents at mid latitudes. Presented here is a specific correlation of ionospheric auroral currents inferred from magnetic field measurements from the Swedish Freja satellite and induced current in the electric power distribution system on the east coast of the United States, in particular the Chalk Point, Maryland, transformer station. The event discussed here registered a Kp level of 6 to 8 and occurred on April 4–5, 1993. An important aspect is that information from both of these space‐ and ground‐based monitoring systems is available automatically and in real time. In addition, satellite data from earlier local times, e.g., data monitored from European ground stations, can give precursor information of later North American geomagnetic activity.
Rapid determination of global moment‐tensor solutions
Authors: Sipkin Stuart A.
Published: February 2004

In an effort to improve data services, the National Earthquake Information Center has begun a program, in cooperation with the Incorporated Research Institutions for Seismology Data Management Center (IRIS DMC), to produce rapid estimates of the seismic moment tensor for most earthquakes with a body‐wave magnitude of 5.8 or greater. Although this program is still undergoing testing and fine‐tuning, an estimate of the moment tensor can usually be produced within 20 minutes of the arrival of the broadband P‐waveform data from the IRIS DMC. Although the speed with which this data can be obtained varies, in many cases a solution can be obtained within two hours of the earthquake. These solutions do not vary significantly from the final solutions determined using the entire network. Because of the manner in which the data and the synthetic seismograms are aligned, the method is insensitive to the effects of timing errors, epicentral mislocation, and lateral heterogeneity in earth structure. This procedure was implemented in May 1993; the results from that month are presented here.
Ozone observations at San Pietro Capofiume, Italy: Preliminary results
Authors: Banzi M. , Carbonara C. , Cervino M.
Published: February 2004

Ozone profiles and column content have been measured routinely since March 1991 at a new ozone monitoring station located in northern Italy at San Pietro Capofiume (44°39′N, 11°37′E). We present preliminary results of one year of observations. As one measure of the reliability of results obtained, total ozone amounts derived from the ozonesonde profiles are compared with total ozone derived from Dobson spectrophotometer and Total Ozone Mapping Spectrophotometer (TOMS) satellite ozone observations.
The roles of time and displacement in the evolution effect in rock friction
Authors: Beeler N. M. , Tullis T. E. , Weeks J. D.
Published: February 2004

Room temperature friction experiments on quartzo‐feldspathic rocks obey a velocity dependence of strength which consists of two opposite‐sensed effects. The second of these effects has a negative velocity dependence and evolves over a characteristic displacement. This evolution effect was originally attributed by Dieterich [1978; 1979] to an underlying time‐dependent process but is often described by either of two empirical evolution laws. One depends explicitly on displacement (slip law) and the other retains time dependence (slowness law). The slip law is favored in representing behavior around steady‐state as seen in velocity stepping experiments. However, in this study slide‐hold‐slide tests conducted at different machine stiffnesses show that the evolution effect depends on time, not slip. For the slowness law the coefficient of time‐dependent strengthening b is measured directly in slide‐hold‐slide tests. Existing empirical evolution laws may not be sufficient to describe both near steady‐state and non steady‐state behavior. Provided a more correct form can be found, time‐dependent evolution may improve frictional models of the seismic cycle by reducing the amount of inter‐seismic slip.
Anisotropy in the center of the inner core
Authors: Vinnik Lev , Romanowicz Barbara , Breger Ludovic
Published: February 2004

We have assembled a collection of PKP data from broadband records of the Geoscope network. This collection is unique because, for the first time, it includes polar paths at epicentral distances between 172° and 177°, for which PKPDF samples the central part of the inner core. After Hilbert transforming the DF branch, the waveforms of PKPAB and PKPDF usually become very similar, and we measure differential travel times with an accuracy of a fraction of a second. The differential (AB‐DF) times for equatorial paths are close to those predicted by PREM, whereas for the polar paths, they are larger by 3 to 6 sec. Absolute DF times confirm that the effect is primarily in the inner core. These observations are compatible with a model of cylindrical anisotropy in the inner core with the axis of symmetry aligned with the Earth's spin axis and an amplitude of 3.5%. They require that the anisotropy extend to the central part of the inner core, confirming extrapolations made by Creager (1992) and ruling out models where anisotropy is confined to the outer 300 km of the inner core (Tromp, 1993).