bluuebunny/crossref_metadata_2025 huggingface dataset:
Energetic ion sputtering effects at Ganymede
Authors: Ip W.‐H. , Williams D. J. , McEntire R. W. , Mauk B.
Published: February 2004

The energy spectra of magnetospheric ion measurements from the Energetic Particle Detectors (EPD) experiment on Galileo during the G2 encounter with Ganymede were used to estimate the ion sputtering rate from the surface of this largest Galilean moon. A combination of the ion composition and the mass‐dependent sputtering yield shows that a total production rate of about 1026 ‐ 4.6 × 1026 H2O molecules/s can be expected from the precipitation of the energetic ions at the polar region. The emission of the sputtered neutral particles will contribute to the formation of an extended exosphere as well as a distributed gas cloud in the Jovian system. Additional sputtering might be possible if an electrostatic potential drop of a few kV forms leading to the acceleration of ionospheric (oxygen) ions towards Ganymede's surface.
Observations of earthward streaming electrons at the trailing boundary of a plasmoid
Authors: Fujimoto M. , Nakamura M. S. , Shinohara I. , Nagai T. , Mukai T. , Saito Y. , Yamamoto T. , Kokubun S.
Published: February 2004

In this paper, we report on highly asymmetric spectrum of electrons observed at the boundary of postplasmoid plasma sheet (PPPS). The data were obtained when GEOTAIL made repeated crossings of the boundary after encountering with a tailward flowing plasmoid at XGSM ∼ −46RE. In the spectrum, electrons in 0.1–1 keV energy range are seen to flow earthward along the lobe‐like field lines into the PPPS counter to more energetic components (ions and electrons) leaking from the PPPS. In the boundary region, earthward streaming electrons are observed even when the energetic leaking components almost disappear, which makes us characterize this region more generally by tailward flowing field aligned currents (FAC). By referring to hybrid code (ion particles, massless electron fluid) results, we propose that the earthward flowing electrons sustain the FAC away from the X‐line (tailward if a spacecraft is located tailward of the X‐line), which is a part of a Hall current loop built‐up in the course of magnetic reconnection.
S‐wave structure of the American Southwest and Mexico from single‐station broadband data
Authors: Jones Laura E. , Paulssen Hanneke , Muyzert Everhard
Published: February 2004

We investigate S velocity structure beneath the Southwestern U.S. and Mexico using upper mantle turning S waves and surface waves. The data are tangential component records from Baja California, Mexican and Central American events recorded at broadband station ANMO (Albuquerque, New Mexico). Study geometry allows investigation of the variation of S structure with source‐receiver azimuth for sources from Baja to Yucatan. The narrow backazimuthal sector studied comprises a transition from oceanic to tectonic to more ‘continent‐like’ structure. We document this transition in the lithosphere and upper mantle to roughly 450 km depth.
Time‐dependent residual deformations associated with the June 9, 1994 Bolivia Earthquake
Authors: Boschi L. , Piersanti A. , Spada G.
Published: February 2004

By means of a spherical Earth model with Maxwell rheology we compute the coseismic and the postseismic displacements associated with the June 9, 1994 Bolivia earthquake. Our results are compared with the coseismic uplift detected by an array of broadband seismic stations in Southern Bolivia and with previous theoretical predictions. Our solution method has been recently employed to study the global deformations due to large lithospheric earthquakes. In contrast to purely elastic Earth models, our method includes the time‐dependent effects associated with mantle relaxation. The results presented here show that the surface deformation due to a deep‐focus earthquake are sensibly magnified by the delayed viscoelastic mantle relaxation. The time‐scales which characterize mantle relaxation and the time evolution of surface observables depend on the rheological profile of the upper mantle, and particularly on the thickness of the viscoelastic asthenosphere.
Preliminary paleomagnetic results from the Upper Carboniferous of Uliastai Block, Inner Mongolia, China
Authors: Chen Haihong , Dobson Jon P. , Heller Friedrich , Hao Jie
Published: February 2004

Paleomagnetic samples from five sites from the Upper Carboniferous Baoligemiao Formation of the Uliastai block (117°10′E, 45°30′N) preserve stable normal and reversed magnetizations, with mean D=138.3°, I=−47.8°, a95=9.7°, k=9.9. IRM acquisition and thermal demagnetization of IRM indicate that the magnetization in these pyroclastic sediments is predominantly carried by magnetite, however, higher coercivity minerals contribute to the remnant magnetization as well. The pole position (53.4°N, 14.8°E) derived from these results is near those of Sino‐Korea and central Mongolia but significantly different from that of Siberia, suggesting that the Uliastai was not a Siberian‐related fragment as traditionally proposed. Instead the block, along with the Mongolia and Sonid blocks, may have moved as a series of north‐facing arc terranes (frontal and remnant arcs) of the Sino‐Korean continent during the Late Paleozoic, possibly an ancient analogue of the Southeast Asian archipelago today.
Measuring ionospheric densities, temperatures, and drift velocities simultaneously at Jicamarca
Authors: Aponte Nestor , Woodman Ronald F. , Swartz Wesley E. , Farley Donald T.
Published: February 2004

Incoherent scatter autocorrelation function measurements are difficult to make in the F region at Jicamarca because of very strong clutter contamination by coherent echoes from unstable plasma waves in the E‐region electrojet that are aligned with the magnetic field. We have developed a more effective way to deal with this clutter that improves the quality of the temperature (and composition when light ions are present) data. Other coherent echoes (much weaker than electrojet echoes but stronger than incoherent scatter) are also received through the antenna sidelobes from field‐aligned irregularities in the 140–170 km altitude range during daytime. These latter echoes have a very narrow bandwidth, and so it is easy to measure their Doppler shift and obtain the vertical plasma drift velocity, which is proportional to the zonal electric field.
Current collection at the shuttle orbiter during TSS‐1R high voltage charging
Authors: Agüero V. M. , Williams S. D. , Gilchrist B. E. , Krause L. Habash , Thompson D. C. , Raitt W. J. , Burke W. J. , Gentile L. C.
Published: February 2004

We compare measurements of collected currents and Space Shuttle Orbiter potentials, taken during the Tethered Satellite System (TSS) missions, with predictions of a numerical model. The model assumes thin potential sheaths about the Orbiter and contributions from both ram and thermal currents. It was originally developed to explain the smaller than expected Orbiter charging detected throughout the first TSS mission (TSS‐1). During periods of the TSS reflight (TSS‐1R) when the Orbiter potential was > −100 V the model effectively described current collection. Deviations from model predictions appeared at more negative potentials. These indicate bounds of applicability for the model and the growing importance of unaccounted physical processes. Data acquired near the time of the tether break suggest that additional current during the break was carried by secondary ions created in collisions between surface‐generated electrons and ambient neutrals within the Orbiter's high‐voltage sheath.
Contour lengthening rates near the tropopause
Authors: Bithell M. , Gray L. J.
Published: February 2004

We present the results of contour advection calculations using winds derived from the UK Universities Global Atmospheric Modelling Programme (UGAMP) model. Contours are initialised using PV values on a set of potential temperature surfaces which span the stratosphere and troposphere in order to examine the mixing properties of stratospheric and tropospheric air on a time‐scale of a few days. We show that the contour stretching rates do not convey any information about the location of the tropopause, although the lower layers of the stratosphere are vigorously mixed with the troposphere over this time. The results suggest that the stratosphere becomes more isolated from the troposphere with increasing potential temperature, with mixing confined to a narrow region in the subtropics at the higher levels (greater than 330K).
Interseismic and coseismic motions in GPS series related to the Ms 7.3 July 13, 1994, Malekula Earthquake, Central New Hebrides Subduction Zone
Authors: Calmant Stéphane , Pelletier Bernard , Pillet Robert , Régnier Marc , Lebellegard Pierre , Maillard Didier , Taylor Fred , Bevis Mike , Recy Jacques
Published: February 2004

On July 13, 1994, an earthquake Ms=7.3 occurred at Malekula, in the New Hebrides archipelago. The GPS data collected across the New Hebrides trench between 1990 and 1996 were processed in order to separate the interseismic and coseismic motions from the drifts related to the convergence with the Australian plate. The GPS‐derived coseismic displacements at the GPS site in Malekula are 49 ± 15 mm southward, 230 ± 30 mm westward and 170 ± 37 mm downward, when the CMT‐derived displacements are 50 mm southward, 210 mm westward and 150 mm downward. Taking into account the interseismic strain accumulation (25 mm/yr at the source established from historical seismicity, 7.5 mm/yr at the GPS site), the strain‐free convergence rate at Malekula is 49 ± 3 mm/yr. Other GPS‐derived convergence rates are 95 ± 1 mm/yr at Efate and 37 ± 2 mm/yr at Santo. These rates imply a regional right‐lateral motion between the Efate and the Santo‐Malekula segments. In contrast, the focal mechanism of the earthquake mostly indicates a left‐lateral motion. Therefore, we hypothesize that the earthquake is related to variations in the interplate coupling along the converging boundary of the Santo‐Malekula segment.
Non‐Maxwellian particle distributions and electromagnetic ion cyclotron instabilities in the near‐Earth magnetotail
Authors: Chaston C. C. , Hu Y. D. , Fraser B. J.
Published: February 2004

Ion distributions in the near‐Earth magnetotail often deviate significantly from a bi‐Maxwellian, the form usually assumed in previous studies of instability in this region of space. Here the electromagnetic dispersion equation for propagation parallel to the background magnetic field is derived from the linearised Vlasov equation for both the generalised bi‐Lorenztian (kappa) distribution and a crescent shaped distribution. For the hot drifting proton distributions in the near Earth magnetotail it is found that increasing deviation from bi‐Maxwellian toward bi‐Lorentzian and crescent shaped forms reduces the maximum temporal growth rates and extends the range of wavenumbers and frequencies where instability occurs. The extension of the range of unstable wavenumbers has the significant effect of increasing convective growth rates in the vicinity of the crossover frequency.
The TSS‐1R Mission: Overview and scientific context
Authors: Stone N. H. , Bonifazi C.
Published: February 2004

The Tethered Satellite System (TSS) program is a binational collaboration between NASA and the Italian Space Agency (ASI) with NASA providing the Shuttle‐based deployer and tether and ASI providing a satellite especially designed for tethered deployment. Twelve science investigations (see Table 1) were supported by NASA, ASI, or the Air Force Philips Laboratory. The goals of the TSS‐IR mission, which was the second flight of the TSS hardware, were to provide unique opportunities to explore (1) certain space plasma‐electrodynamic processes—particularly those involved in the generation of ionospheric currents, and (2) the orbital mechanics of a gravity‐gradient stabilized system of two satellites linked by a long conducting tether.

TSS‐IR was launched February 22, 1996 on STS‐75 into a 300‐km, circular orbit at 28.5° inclination. Satellite flyaway occurred at MET 3/00:27 and a unique data set was obtained over the next 5 hours as the tether was deployed to a length of 19,695 m. At MET 3/05:11, during a day pass, the tether suddenly broke near the top of the deployer boom. The break resulted from a flaw in the tether insulation which allowed the ignition of a strong electrical discharge that melted the tether. The operations that had begun at satellite flyaway, however, allowed significant science to be accomplished.
Is the geoeffectiveness of the 6 January 1997 CME predictable from solar observations?
Authors: Zhao X. P. , Hoeksema J. T.
Published: February 2004

We present a prediction scheme for specifying the duration and maximum strength of the southward IMF within a magnetic cloud from observations of the disappearing filament associated with the coronal mass ejection and the photospheric magnetic field made near the filament disappearing. Using this scheme we were able to predict that the Earth directed 6 January 1997 coronal mass ejection would be geoeffective. We expected that the southward IMF interval would have a maximum strength of −13±5 nT and a duration of 14±5 hours. This compares favorably with the WIND observations of −15 nT and 13 hours.
Negative shuttle charging during TSS 1R
Authors: Gentile L. C. , Burke W. J. , Huang C. Y. , Machuzak J. S. , Hardy D. A. , Olson D. G. , Gilchrist B. E. , Lebreton J.‐P. , Bonifazi C.
Published: February 2004

We studied 21 intervals during the TSS 1R deployment with a 15 Ω or 25 kΩ resistor connecting the tether to shuttle ground. Ion spectral peaks detected by the Shuttle Potential and Return Electron Experiment indicate that the shuttle consistently charged negatively with respect to the local plasma. With the 15 Ω shunt in the circuit, shuttle potential, Φs, decreased from −17 to −245 V as tether length, L, increased to 2.6 km. Current in the circuit depended strongly on ionospheric density. With the 25 kΩ resistor in place, Φs ≈ −300 V in the low density, nightside ionosphere with L = 5.1 km. Near local noon Φs ≈ −80 V with L = 17.2 km. The shuttle charged to ∼−600 V during two dawn terminator crossings, one with and one without thruster firings. As on TSS 1, firings of two aft vernier thrusters significantly increased |Φs|. In the case without thruster firings, simultaneous variations of Φs, tether current, and the inferred satellite potential are consistent with strong azimuthal and vertical ionospheric density gradients. These are the first known direct measurements of strong negative shuttle charging.
Energy‐time dispersed charged particle signatures of dynamic injections in Jupiter's inner magnetosphere
Authors: Mauk B. H. , Williams D. J. , McEntire R. W.
Published: February 2004

We report on the first detection of energy‐time dispersed charged particle signatures of dynamic injections within Jupiter's inner magnetosphere. They were observed by the Energetic Particle Detector on the Galileo spacecraft. The signatures documented here were detected most clearly in ∼15–880 keV electrons when Galileo was near local noon at a radial position of ∼11 RJ. On the basis of the character of the signatures (∼60‐min signatures within each energy channel and up to ∼90‐min time dispersions between channels), the injection disturbances occurred 24–33 h prior to the time of the detections and spanned ∼2.5 h (<40°) of azimuth at the time of the disturbances. Possible generation mechanisms and similarities with Earth magnetosphere events are discussed.
OH, HO2, and NO in two biomass burning plumes: Sources of HOx and implications for ozone production
Authors: Folkins Ian , Wennberg P. O. , Hanisco T. F. , Anderson J. G. , Salawitch R. J.
Published: February 2004

The ER‐2 made two descents through upper tropospheric biomass burning plumes during ASHOE/MAESA. HOx (= OH + HO2) concentrations are largely self‐limited outside the plumes, but become progressively more limited by reactions with NOx (= NO + NO2) at the higher NOx concentrations inside the plumes. Sources of HOx in addition to H2O and CH4 oxidation are required to balance the known HOx sinks both in the plumes and in the background upper troposphere. HOx concentrations were consistently underestimated by a model constrained by observed NOx concentrations. The size of the model underestimate is reduced when acetone photolysis is included. Models which do not include the additional HOx sources required to balance the HOx budget are likely to underestimate ozone production rates.
Electron microscope analysis of residual particles from aircraft contrails
Authors: Twohy Cynthia H. , Gandrud Bruce W.
Published: February 2004

Ice crystals larger than about 5 µm diameter were separated from interstitial particles in aircraft contrails and evaporated. Residual particles larger than 0.1 µm were analyzed by electron microscopy. Soot, metals, and volatile organic substances, apparently from the aircraft exhaust, were found. However, the residual particles also contained high percentages of minerals, thought to be crustal in origin, that were often mixed with sulfur. The percentage of particles in our samples (representing the larger residual particles from relatively large ice crystals) identified as exhaust‐derived and the percentage apparently derived from the ambient aerosol were roughly equal, suggesting that ambient particles may be important in contrail formation. Possible explanations for this are presented.
Suprathermal electrons observed on the TSS‐1R satellite
Authors: Winningham J. D. , Stone N. H. , Gurgiolo C. A. , Wright K. H. , Frahm R. A. , Bonifazi C. A.
Published: February 2004

Particle measurements up to 27,000 eV were made on the TSS‐1R (Tethered Satellite System) satellite. The TSS satellite developed a positive bias due to the Lorentz force. It was the intent that electron measurements on the TSS satellite could be used to track the spacecraft potential and collected current. What was observed was quite different. Accelerated ionospheric electrons were observed to only ∼70 eV even though larger spacecraft potentials were observed by other diagnostics on the TSS satellite. When observed they agreed with these independent measurements of the potential. In addition to the anticipated accelerated thermals, a suprathermal population of electrons was observed to be centered around 200 eV. This population exhibited a 4 orders‐of‐magnitude increase in intensity as the spacecraft potential exceeded the O+ ram energy. The disappearance of the accelerated thermals is explained by the observation that the suprathermal flux becomes larger in magnitude, thus hiding the thermals. However the suprathermals cannot be the dominant current carriers if they are the result of a DC process as their calculated current magnitude exceeds that observed. These results are best explained if one assumes an AC acceleration of the suprathermal electrons whose free energy is derived from the differential drift between electrons and ions.
The small‐comet hypothesis: An upper limit to the current impact rate on the moon
Authors: Grier Jennifer A. , McEwen Alfred S.
Published: February 2004

Frank et al. [1986b] and Frank and Sigwarth [1993] hypothesized the intense bombardment of the terrestrial atmosphere by small comets. Their model requires that the Moon is impacted by small comets (107‐108 g) at a rate of almost one per minute. We calculate that an object of this mass, even with an exceedingly low density and relatively low velocity, will nevertheless produce a crater at least 50 m in diameter. These craters will excavate immature lunar soil and produce a very bright spot with a diameter of at least 150 m. If low‐density comets exist that might not create deep craters [O'Keefe and Ahrens, 1982], they will nevertheless disturb the regolith sufficiently to create detectable bright spots. If the small‐comet hypothesis is correct then the near‐global lunar imaging returned by Clementine in 1994 should reveal ∼107 bright spots in locations where craters are not present in images acquired in the 1960's and early 1970's. We find no new bright spots in a carefully‐studied area of 5.2×104 km², so an upper limit to the current cratering rate by small comets is 33/yr, ∼104 below that expected if the small‐comet hypothesis were valid.
Time‐frequency decomposition of signals in a current disruption event
Authors: Lui A. T. Y. , Najmi A.‐H.
Published: February 2004

Wavelet transform has recently been developed to the level of sophistication suitable for application to signal processing in magnetospheric research. We explore this new technique in decomposing signals in the time‐frequency domain by first conducting continuous wavelet transform on a test signal to show its ability to resolve multiple‐frequency components embedded within white noise of half the amplitude as the signal. We then use this tool to examine the large‐amplitude magnetic fluctuations observed during a current disruption event. The results show the current disruption to be a multiscale phenomenon, encompassing low‐ as well as high‐frequency components. The lowest‐frequency component appears to behave quite independently from the higher‐frequency components. The analysis shows for the first time that in current disruption the high‐frequency components constitute a broadband excitation with a nonstationary nature, i.e., some oscillations appear to cascade from high to low frequency as time progresses.
UV absorption cross sections for SO3
Authors: Burkholder James B. , McKeen Stuart
Published: February 2004

Room temperature gas phase absorption cross sections for SO3 have been measured over the wavelength range 195 to 330 nm using a diode array spectrometer. The SO3 spectrum is continuous with weak diffuse vibrational band structure in the 225 to 295 nm region. Atmospheric photolysis rate calculations show that photolysis of SO3 in the 190 to 230 nm actinic window is important in determining the sulfur partitioning in the upper stratosphere.
MAHRSI observations of nitric oxide in the mesosphere and lower thermosphere
Authors: Stevens Michael H. , Conway Robert R. , Cardon Joel G. , Russell James M.
Published: February 2004

In November, 1994, the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) observed the distribution of NO between the altitudes of 76 and 140 km by measuring limb intensity profiles of solar resonance fluorescence in the NO A ²Σ → X ²II (1,0) γ band near 215 nm. The observations were made from the ASTRO‐SPAS (Shuttle Pallet Satellite) spacecraft which was deployed and retrieved by the space shuttle. The data provided a seven hour snapshot of lower thermospheric and mesospheric NO from sunrise near 48°S to sunset near 61° N latitude following a period of low solar and high geomagnetic activity. Inferred peak lower thermospheric NO densities ranged from 3 × 107 cm−3 near the equator to 2 × 108 cm−3 at high northern latitudes, roughly consistent with previous observations for the same conditions. Individual vertical density profiles showed substantial structure and large orbit to orbit variations, suggesting that the distribution of mesospheric and lower thermospheric NO is dynamically influenced.
On the steady‐state assumption for the energy distribution function of the nonthermal N(4S) atoms and the efficiency of NO production by these atoms in the terrestrial thermosphere
Authors: Dothe H. , Sharma R. D. , Duff J. W.
Published: February 2004

The time dependent energy distribution functions (EDF) of N(4S) atoms for altitudes greater than 100 km at 1400 hr local time are calculated by solving the time dependent Boltzmann equation. At time t=0 the time dependent sources and sinks are switched on into a Maxwell‐Boltzmann distribution of N(4S) atoms and the time dependence of the EDF is followed by solving the Boltzmann equation. It is found that the non‐Maxwellian tail of the EDF reaches a steady‐state in 0.01 s giving the fraction of nascent N(4S) atoms that react with O2 before the establishment of steady‐state to be less than 1%. The number of NO molecules produced per second, after the establishment of steady‐state, by the non‐Maxwellian tail of the EDF is at most about 3% of the number of N(4S) atoms in the sources. The last fraction, often referred to as “NO reaction efficiency”, is about an order of magnitude smaller than that given in recent literature. An important consequence of this study is that the models still calculate less NO in the mesosphere and lower thermosphere than is measured.
Single particle analyses of ice nucleating aerosols in the upper troposphere and lower stratosphere
Authors: Chen Yalei , Kreidenweis Sonia M. , McInnes Lynn M. , Rogers David C. , DeMott Paul J.
Published: February 2004

A newly developed instrument was deployed on the NASA DC‐8 airborne laboratory during the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS, Spring 1996) to detect and collect heterogeneous ice nucleating particles (IN) in the upper troposphere and lower stratosphere. The elemental compositions of both ambient particles and IN were determined with single particle analysis using analytical electron microscopy. IN collected during flights on May 4 and 8 had enhanced number fractions of metallic, crustal, and carbonaceous particles, compared with the ambient aerosol population, and were relatively deficient in sulfur‐containing particles. IN sampled within aircraft exhaust and contrails had higher number fractions of metallic particles, which includes those rich in Zn, Al, and Ti, than the IN sampled in air that was not immediately affected by aircraft exhaust.
A case study of oppositely propagating Alfvénic fluctuations in the solar wind and magnetosheath
Authors: Sibeck D. G. , Takahashi K. , Kokubun S. , Mukai T. , Ogilvie K. W. , Szabo A.
Published: February 2004

MHD solutions indicate that solar wind Alfvénic fluctuations striking the bow shock should launch a variety of disturbances into the magnetosheath, including both forward (antisunward) and reverse (sunward) propagating Alfvénic fluctuations. We present the first observational evidence of this prediction. This case study presents observations of the Wind spacecraft of Alfvénic fluctuations propagating antisunward along the away sector Parker spiral interplanetary magnetic field (IMF) on April 26 to 27, 1995. Simultaneous Geotail solar wind observations confirm the presence of Alfvénic fluctuations propagating along the spiral IMF, but Geotail magnetosheath observations indicate Alfvénic fluctuations propagating in the opposite direction relative to the draped, prenoon, magnetic field. The reversal in wave propagation direction at the bow shock provides striking evidence for the MHD model of waveshock interaction.
Formation of reconnection layer at the dayside magnetopause
Authors: Lin Y. , Xie H.
Published: February 2004

A two‐dimensional (2‐D) hybrid simulation is carried out to study the formation and structure of the reconnection layer at the dayside magnetopause. The result is shown for a case with a zero guide field (By = 0) in the magnetosheath and magnetosphere. A quasi‐steady reconnection layer develops behind a leading transient bulge in the outflow region of the reconnection, in which an intermediate shock is present on the magnetosheath side. The structure of the intermediate shock varies with the distance from the X line along the magnetopause. An accelerated plasma flow is present in the boundary layer on the magnetospheric side of the intermediate shock. The ion transport across the magnetopause boundary layer during the formation of the reconnect ion layer is also investigated.
HALOE observations of a slowdown in the rate of increase of HF in the lower mesosphere
Authors: Considine G. D. , Deaver L. , Remsberg E. E. , Russell J. M.
Published: February 2004

A statistical analysis of monthly averaged HF measurements from HALOE shows definite signs of a slowdown of the increase in HF at 55 km. The data used in this study are monthly averaged HF data from a latitude band from 50N to 50S at an altitude of 55 km. We find that the combination of a third‐order polynomial, an annual and semi‐annual cycle, and a 900‐day cycle provides a good model of the data. The changes in the HF trend are consistent with the trends of CFC‐11 and CFC‐12 in the troposphere in the early 1990's, adjusted by an estimated lag time to account for transport from the troposphere up to 55 km.
Enhanced UV penetration due to ozone cross‐section changes induced by CO2 doubling
Authors: Yung Yuk L. , Jiang Yibo , Liao Hong , Gerstell M. F.
Published: February 2004

Models predict that CO2 doubling in the atmosphere cools the stratosphere by as much as 10°C. We argue that this effect alone, through the temperature dependence of the ozone spectrum, can result in an increase of a few percent in UV‐B (280–320 nm) penetration at the Earth's surface. The increase in Erythema‐weighted UV radiation is about 1%. Future spectral observations of UV at the surface could distinguish this effect from any result of changes in ozone abundance.
Near real‐time GPS sensing of atmospheric water vapor
Authors: Rocken Christian , Van Hove Teresa , Ware Randolph
Published: February 2004

We describe sensing of atmospheric column water vapor in near real‐time using the Global Positioning System (GPS). We use predicted GPS orbits for automated computation of vertical column water vapor within 30 minutes of GPS data collection. Based on a 4 month comparison, near real‐time GPS column water vapor agrees with radiosondes and radiometers within 2 mm rms. Our near real‐time column water vapor data are posted hourly at www.unavco.ucar.edu. They are available for assimilation in numerical weather models and for other applications.
Total ozone trends at sixteen NOAA/CMDL and Cooperative Dobson Spectrophotometer Observatories during 1979–1996
Authors: Komhyr W. D. , Reinsel G. C. , Evans R. D. , Quincy D. M. , Grass R. D. , Leonard R. K.
Published: February 2004

Ozone trends, derived from 1979–1996 Dobson spectrophotometer total ozone data obtained at five U.S. mainland midlatitude stations, averaged −3.4, −4.9, −2.6, −1.9, and −3.3%/decade for winter, spring, summer, and autumn months, and on an annual basis, respectively. At the lower latitude stations of Mauna Loa and Samoa, corresponding‐period annual ozone trends were −0.4 and −1.3%/decade, respectively, while at Huancayo, Peru, the 1979–1991 annual trend was −0.9%/decade. A linear trend approximation to ozone changes that occurred since 1978 during austral daylight times at Amundsen‐Scott (South Pole) station, Antarctica, yielded a value of −12%/decade. By combining 1979–1996 annual trend data for three U.S. mainland stations with trends for the sites derived from 1963–1978 data, it is estimated that the ozone decrease at U.S. midlatitudes through 1996, relative to ozone present in the mid‐1960s, was −6.7%. Similar analyses incorporating South Pole data obtained since 1963 yielded an ozone change at South Pole (daylight observations) through 1996 of approximately −25%. South Pole October total ozone values in 1996 were lower than mid‐1960s October ozone values by a factor of two. Trend data are also presented for several shorter record period stations, including the foreign cooperative stations of Haute Provence, France; Lauder, New Zealand; and Perth, Australia.
Response of a volcanic conduit to step‐like change in magma pressure
Authors: Fukao Yoshio , Fujita Eisuke , Hori Sadaki , Kanjo Kenji
Published: February 2004

Freely damped oscillations associated with strain offsets were observed by a nearby volumetric strainmeter during the 1986 Izu‐Oshima Volcano eruption, Japan. These events are interpreted as a response of the magma‐filled conduit to step‐like changes in magma pressure. There were dramatic changes in the characteristic frequency of oscillation and the polarity of initial motion before and after the 6‐hour interval of the enormous ground deformation due presumably to magma intrusion. The frequency changed from 42.6 to 21.3 mHz and the polarity changed from contraction to expansion. We propose a conceptual conduit model to explain this polarity reversal, where magma is episodically supplied to the conduit before but is episodically drained back to the reservoir after an extensive magma escape away from the reservoir as dike intrusion. Stress caused by the dike intrusion is large enough to break the lid of the conduit, thus to change a boundary condition. This change in boundary condition reduces the frequency of oscillation by a factor of 2. In this model longitudinal wave speed of the magma fluid is 340 m/s if the conduit length is taken to be 4 km.
Deliquescence of sulfuric acid tetrahydrate following volcanic eruptions or denitrification
Authors: Martin Scot T. , Salcedo Dara , Molina Luisa T. , Molina Mario J.
Published: February 2004

A thermodynamic model is employed to investigate the effects of cooling sulfuric acid tetrahydrate (SAT) when the polar stratosphere is perturbed by denitrification or volcanic eruptions. Also, survey experiments are carried out to study the plausibility of the predictions of this model. In contrast to an atmosphere rich in HNO3 for which Koop and Carslaw [1996] calculated that SAT deliquesces upon cooling to form a ternary solution, in a denitrified atmosphere the liquid begins to form ∼3 K colder, and SAT is not predicted to deliquesce completely above the ice frost point. Likewise, in an atmosphere with a high sulfate loading, solid/liquid aerosols are predicted to coexist over a large temperature range. For these two cases, SAT particles should thus deliquesce only partially upon cooling, and hence, should return to solid form upon warming. Furthermore, the results of laboratory experiments suggest that HNO3‐induced deliquescence of SAT might be too slow to matter even under normal stratospheric conditions.
Green plants: A terrestrial sink for atmospheric CH3Br
Authors: Jeffers Peter M. , Wolfe N. Lee , Nzengung Valentine
Published: February 2004

Methyl bromide is reactively removed from air by the foliage of all 9 herbaceous, 18 deciduous, and 12 coniferous plants we have tested, in a process that appears enzymatic. Excised plant leaves yielded removal rates directly proportional to leaf surface area and first‐order in CH3Br concentration from 10 ppmv to 500 pptv, the current limit of our experimental technique. Observed rate constants for different plants vary within a factor of about 100 with a lower value of 1×10−3 hr−1cm−2 in systems where the rate is not diffusion limited. This sink for atmospheric CH3Br could be significant in calculations of the global methyl bromide budget.
Resistivity structure of the Olympic Mountains and Puget Lowlands
Authors: Aprea Claudia , Unsworth Martyn , Booker John
Published: February 2004

Magnetotellurics has been used to study of the geo‐electric structure of the Olympic Mountains and Puget Lowland. Data were collected along an west‐east line extending from the Pacific Ocean to the Cascade Mountains. The smoothest resistivity model consistent with the data suggests that subduction of the Olympic Mountains accretionary complex (Core rocks) has been prevented by a 30+km thick sequence of volcanic rocks. This may effectively couple the Juan de Fuca and North American Plates and may explain the concentration of crustal earthquakes beneath the Puget Lowland.
A comparison of precipitation datasets for the Amazon Basin
Authors: Costa Marcos Heil , Foley Jonathan A.
Published: February 2004

Six different estimates of precipitation (three based entirely on rain gauge measurements, one based on a combination of rain gauge measurements and satellite data, and two based on reanalyzed meteorological datasets) for the Amazon basin are compared. Altogether, these different estimates have a mean value of 2130 mm/yr. The long‐term spatial patterns of annual precipitation within the basin are in good agreement for datasets based on rain‐gauges, while data from the reanalyzed meteorological datasets appear to have significant spatial biases resulting from the influence of the spectral representation of topography. While the long‐term average precipitation climatology of the Amazon basin appears to be consistently described by the six different datasets, the interannual variability in precipitation (as represented by the four datasets that contain precipitation time‐series information with various lengths of record) has significant regional discrepancies. These results suggest that some caution be exercised when using precipitation time‐series data over the Amazon basin.
Contrail properties derived from high‐resolution polarization lidar studies during SUCCESS
Authors: Sassen Kenneth , Hsueh Ching‐yu
Published: February 2004

During the April 1996 SUCCESS field campaign, our ground‐based polarization lidar studied a variety of contrails ranging from a new NASA DC‐8 contrail to persisting contrails from commercial jet aircraft that had spread into an almost invisible cirrostratus sheet. What distinguishes these contrails from natural cirrus is their tendency to remain thin (∼50–500 m), and to generate strong laser backscattering and depolarization, often along with solar coronas, even an hour or more after formation. Lidar depolarization ratios in persisting contrails ranged from ∼0.3–0.7. Contrail‐cirrus clouds composed of high numbers of small (20–30 µm) particles would satisfy these findings, which has implications for comprehending their radiative and climatic effects.
Large‐scale Rossby wave in the mid‐latitude South Pacific from altimetry data
Authors: Wang L. , Koblinsky C. , Howden S. , Beckley B.
Published: February 2004

We present observations of large‐scale Rossby wave propagation in the mid‐latitude South Pacific (25°S) from analyzing 4 years of TOPEX/POSEIDON altimetry data. Using wavelet transform we separate phase propagation from amplitude modulation. The dominant Rossby wave has a wavelength of about 40° with a period close to 2 years (phase speed ∼6.4 cm/s). Its amplitude modulates both interannually and intraannually. In addition, we also found a shorter‐scale Rossby wave with a wavelength of about 16° and a period close to 9 months.
TMTM simulations of tides: Comparison with UARS observations
Authors: Yudin Valery A. , Geller Marvin A. , Khattatov Boris V. , Ortland David A. , Burrage Mark D. , McLandress Charles , Shepherd Gordon G.
Published: February 2004

This paper presents combined model‐data interpretation of the High Resolution Doppler Imager (HRDI) and Wind Imaging Interferometer (WINDII) wind, temperature and airglow data using the tuned mechanistic tidal model (TMTM) approach, including calculation of the nighttime oxygen emission rates induced by the simulated tides. This is the first demonstration of the consistency of the tidal signatures in the HRDI/WINDII temperature, airglow and wind observations in the mesosphere and lower thermosphere (MLT). This analysis gives increased confidence in these UARS measurements and also in our TMTM methodology.
Monitoring the comprehensive Test Ban Treaty: Possible ambiguities due to meteorite impacts
Authors: Chyba Christopher F. , van der Vink Gregory E. , Hennet Christel B.
Published: February 2004

For seismic magnitudes in the range of monitoring interest for the Comprehensive Test Ban Treaty, hypervelocity meteorite impacts will be detected about once every decade. Such detections could cause concern if they were difficult to distinguish from explosions and were associated with potential terrorist activity or treaty violations.
An upper limit on the production of N2O from the reaction of O(¹D) With CO2 in the presence of N2
Authors: Wingen Lisa M. , Finlayson‐Pitts Barbara J.
Published: February 2004

While the major sources and sinks of N2O are known, there is debate concerning additional processes. A new source of N2O was proposed, reaction of N2 with excited CO3*, formed from O(¹D) and CO2. Mixtures of O3, CO2, N2, and O2 at total pressures of 1 atm were photolyzed at 254 nm to form O(¹D). The decrease in O3 and a search for N2O formation were carried out using FTIR at 298 K and ∼264 K. N2O was not detected at either temperature. Upper limits were derived for the rate constant of the reaction CO3* + N2 → N2O + CO2, k≤5.5×10−13 cm³ molecule−1 s−1 at 298 K and k≤4.2×10−13 cm³ molecule−1 s−1 at 264 K. Applying the rate constant at 264 K to typical stratospheric conditions at the spring equinox, 17 km and 40°N, the N2O formation rate was calculated to be ≤1 molecule cm−3 s−1. These experiments did not use isotopically heavy reactants and therefore may underestimate the N2O yield. It is assumed that the results of these studies are applicable to stratospheric conditions. It is also assumed that N2O is not destroyed as it is formed by unrecognized secondary reactions. However, within these constraints, the upper limit suggests that this reaction is not a significant source of N2O.
Is there a quasi‐biennial oscillation in tropical deep convection?
Authors: Collimore Christopher C. , Hitchman Matthew H. , Martin David W.
Published: February 2004

We investigate the possibility that the stratospheric Quasi‐Biennial Oscillation (QBO) modulates deep convection in the tropics. Interannual variations of outgoing longwave radiation (OLR) in the tropics during 1975–87 are compared with stratospheric zonal winds at Singapore (a measure of the QBO), and with the Tahiti‐Darwin sea level pressure difference (the Southern Oscillation Index, or SOI). A monthly time series of anomalous OLR was constructed for regions of consistently low OLR, thus targeting areas of chronic deep convection. This “chronic cold” index and the SOI correlate at −0.6 for zero lag. The “chronic cold” index correlates with 30 hPa Singapore winds at +0.3 and with 50 hPa‐70 hPa wind differences at +0.4, both near zero lag. These results are not inconsistent with the hypothesis that deep convection may be enhanced in chronically cold areas when QBO westward shear exists in the lower stratosphere, and diminished during eastward shear.
FAST‐ Geotail correlative studies of magnetosphere ionosphere coupling in the nightside magnetosphere
Authors: Sigsbee K. , Cattell C. A. , Lysak R. L. , Carlson C. W. , Ergun R. E. , McFadden J. P. , Mozer F. , Elphic R. C. , Strangeway R. J. , Tsuruda K. , Yamamoto T. , Kokubun S. , Fairfield D. , Pfaff R. , Parks G. , Brittnacher M.
Published: February 2004

Data from conjunctions between FAST and Geotail were used to examine the physical processes which mediate coupling between the magnetotail at 30 RE and the nightside auroral zone near 1.5 RE. During one conjunction, Geotail observed a large scale recovery of the plasma sheet and several partial thinnings. Two of these encounters with the plasma sheet boundary were recorded by Polar at high latitudes on the dawn flank, indicating the global nature of the plasma sheet motions. Wavelet analysis of the FAST and Geotail electric and magnetic field data revealed low frequency waves which may be involved in magnetosphere‐ionosphere coupling. A brief electromagnetic pulse with a frequency of 0.9 Hz consistent with the Alfvénic structures discussed by Lysak [1997] was observed by FAST. Oscillations near this frequency were also observed in the Geotail electric field data. Signatures consistent with field line resonances in the frequency range 0.03 to 0.05 Hz were recorded by both FAST and Geotail. This is the first time these types of structures have been observed simultaneously in the auroral zone and the magnetotail.
In‐flight measurement of aircraft non‐methane hydrocarbon emission indices
Authors: Slemr F. , Giehl H. , Slemr J. , Busen R. , Schulte P. , Haschberger P.
Published: February 2004

Concentrations of non‐methane hydrocarbons (NMHC) and CO were measured in exhaust plumes of the DLR experimental aircraft ATTAS equipped with Rolls Royce M 45H Mk50l engines. The emission indices (EI) of individual light NMHC were determined from ratios of NMHC and CO concentration enhancements measured in grab samples and the concurrent in‐flight measurements of EI of CO by FTIR emission spectroscopy. Alkenes and alkynes generated by cracking of larger NMHC molecules and aromatic compounds originating from unburnt fuel constituted a larger and a smaller fraction of the NMHC emissions, respectively.
The flux of tidal energy across latitude 60°S
Authors: Ray Richard D. , Egbert Gary D.
Published: February 2004

How and where the ocean tides dissipate their energy are longstanding questions with both oceanographic and astronomical implications. Two decades ago, Doake suggested that flexing of Antarctic ice shelves by the underlying ocean tide is an important energy sink, perhaps accounting for over half the global dissipation rate. Observational constraints on Antarctic dissipation have been scarce. Here two new and complementary ocean‐tide models, both derived from Topex/Poseidon satellite altimeter measurements, are used to determine the flux of tidal energy across 60°S toward the Antarctic coastline. Our results show relatively small fluxes and they therefore rule out Doake's suggestion: Antarctica is an insignificant sink in the global tidal energy budget.
Dynamics of the outer radiation belt
Authors: Selesnick R. S. , Blake J. B.
Published: February 2004

Radial profiles of electron intensity and phase space density in the energy range of ∼0.7 to 8 MeV, between L values of 3 and 9, show that particle injections followed by fast radial diffusion lead to the main part of the outer radiation belt near L=4 to 5 during active periods. In quiet times the belt is supplied by inward diffusion from an external source. Various combinations of these two basic configurations are also seen.
Localized brightenings in Jupiter's Radiation belts resulting from Comet SL9 impacts
Authors: Sault R. J. , Leblanc Yolande , Dulk George A.
Published: February 2004

Using a technique that forms three‐dimensional brightness reconstructions of Jupiter's radiation belts, we analyze observations at the time of the comet Shoemaker‐Levy 9 impact with Jupiter in 1994. The 3‐D reconstructions provide far more information about an object than does conventional 2‐D astronomical imaging. Near Jupiter's magnetic equator, the 3‐D reconstructions of the comet‐perturbed state reveal that: i) the increase in brightness was localized near the longitudes of individual impacts or groups of impacts; ii) the brightenings did not start immediately after a given impact, but built up over one or two days; iii) the distance of the brightenings from Jupiter is related to the magnetic field lines where the impacts occurred; iv) the brightenings drifted little or not at all over the course of days; v) 10 days after the first impact, the brightenings were still observable, although with less intensity. These findings have important implications regarding the physical processes linking comet impacts to their effects on Jupiter's radiation belts.
Ulysses observations of a discrete wavepacket upstream of an interplanetary shock
Authors: Lucek E. A. , Balogh A.
Published: February 2004

We present a single example of a previously unidentified type of upstream wave structure, found several minutes ahead of a forward propagating, oblique interplanetary shock observed on day 6, 1992, using Ulysses magnetometer data. The wave appears as an isolated high frequency wavepacket associated with a larger scale compressive structure. In the region between the wavepacket and the shock the magnetic field is moderately, but significantly, compressed and deflected suggesting the existence of a foreshock. The wavepacket is dispersive and wavelet analysis shows a near linear decrease in frequency from 0.3 to 0.1 Hz, continuing across the large scale structure which is assumed to be the source of these waves. We suggest that the feature is similar in nature to the shocklet and associated discrete wavepacket commonly found in planetary foreshocks, but further examples are required before a definite conclusion can be reached.