bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional horizontal deformation associated with the March 2, 1987, Edgecumbe Earthquake, New Zealand
Authors: Crook C. N. , Hannah J.
Published: February 2008

Following the March 2 1987 Edgecumbe earthquake (magnitude ML 6.3) angle and distance measurements were made from 4 previously observed survey stations to a further 10 stations to determine the regional horizontal deformation associated with the event. The surface faulting associated with the earthquake was largely confined to the Rangitaiki Plain, a low lying flood plain on which four of the survey stations are located. These stations show large relative displacements which imply local compression of at least 100ppm. The stations off the Plain show a more consistent pattern of behaviour which may be characterised as the stations to the NW of the Plain having moved about 0.7m in direction N20°W with respect to the stations to the SE. The displacements can be modelled by a 28km long by 2.3km wide rectangular fault striking at N40°E, with a 39°dip to the NW and with the top at depth 3km, on which 1.4m right‐lateral strike‐slip and 5.4m normal dip‐slip movement occurred. Though the model fault plane is unrealistically narrow, its extrapolation is consistent with the hypocentre location, aftershock distribution, and focal mechanism observed for the event.
Paleomagnetism of the Cambro‐Ordovician Arbuckle Group and associated deposits in the southern Oklahoma Aulacogen: Evidence for block rotations
Authors: Elmore R. Douglas , Nick Kevin E. , Cochran Karen A. , Crawford Lisa D.
Published: February 2008

The magnetization in hydrocarbon‐impregnated Arbuckle Group limestones from the southern margin of the Southern Oklahoma Aulacogen (Limestone Hills) is secondary and resides in magnetite. The magnetization (Declination/Inclination=128°/2°, α95=7.6°, k=79) fails a fold test and is post Pennsylvanian. The corresponding pole position (146°E, 30°N), however, does not coincide with the post‐Pennsylvanian Apparent Polar Wander Path (APWP). Some Permian speleothems that fill caves in these rocks contain magnetizations that are also anomalous. Shallow remanent inclinations from the folded limestones and speleothems suggest that the most likely time of remanence acquisition was the Permian. The directions are at least 30° in declination from the expected directions based on the inferred ages of the magnetizations. This discrepancy can be explained by a horizontal counterclockwise rotation, consistent with left‐lateral wrench faulting, during deformation of the aulacogen.
Observation of electromagnetic ion cyclotron waves and hot plasma in the polar cusp
Authors: Erlandson R. E. , Zanetti L. J. , Potemra T. A. , André M. , Matson L.
Published: February 2008

On July 24, 1986 narrow band magnetic field fluctuations were observed by VIKING near the apogee altitude of 13,500 km in the polar cusp region during a period of strong southward interplanetary magnetic field (IMF). The VIKING magnetic field experiment obtained vector magnetic field measurements up to nearly the proton cyclotron frequency (fH=28 Hz). Simultaneously, magnetosheath‐like electrons and ions as well as an upward‐flowing field‐aligned current were observed. The most intense flux of electrons and ions were colocated with a 35 nT depression in the total magnetic field strength of 1860 nT, interpreted as a diamagnetic effect. The density of magnetosheath‐like plasma, estimated from the diamagnetic depression, reached ∼500 cm−3. This extremely high density was also consistent with total plasma density estimates using high frequency waves. Magnetic field fluctuations were observed from 18 to 27 Hz and occurred when the magnetic field strength depression was maximum. These waves were left‐hand elliptically polarized with ellipticity between 0.2 and 0.3 and may propagate in the Alfvén‐ion cyclotron branch of the cold electromagnetic dispersion relation. Possible free energy sources included anisotropies in the electron and ion distributions.
A relationship between radar backscatter and aerodynamic roughness: Preliminary results
Authors: Greeley Ronald , Lancaster Nicholas , Sullivan Robert J. , Saunders R. Stephen , Theilig Eilene , Wall Steven , Dobrovolskis Anthony , White Bruce R. , Iversen James D.
Published: February 2008

The ability of the wind to move particles and the flux of windblown sand are both dependent on the topographic roughness of the surface, as measured by the aerodynamic roughness (zo). For most surfaces, topographic roughness controls many of the characteristics of the radar return, and the magnitude of the radar backscatter can be regarded as a measure of the surface roughness at or near the wavelength scale. Radar backscatter data may therefore be useful in obtaining a value of aerodynamic roughness which can be used to assess aeolian sediment transport via remote sensing. In this study, calibrated LHH, CHH and KuVV radar data were used to derive characteristic backscatter coefficients (σo) for three lava flow units, an alluvial fan, and a playa surface. Preliminary analyses show that values of σo and zo both increase with topographic roughness and that there is a good correlation between the two coefficients. This correlation suggests that it may be possible to assess aerodynamic roughness directly from radar data.
Detectability of very slow earthquake from tide gauge records
Authors: Satake Kenji , Shimazaki Kunihiko
Published: February 2008

A very slow earthquake or crustal deformation with a rise time longer than the period of the free oscillation of the Earth is difficult to observe on seismograms. However, we show that it can be detected from tide gauge records, because the free oscillation of an ocean basin such as the Japan Sea contains longer eigenperiods than those of the solid Earth. Actually, such an oscillation was excited by the Niigata earthquake of 1964 and recorded on tide gauges. Comparison of the tide gauge spectra of the free oscillation with the noise spectra shows that the free oscillation of the Japan Sea excited by a magnitude 7 class earthquake can be detected in the present tide gauge observation system. Further, a simulation for a very slow earthquake with a source process time of 1 hour shows that the slow event, which cannot be detected on seismograms, is detectable on tide gauges. However, the smaller the slip, the more difficult it is to detect the movement because of the limited dynamic range of the existing tide gauge system. If a slow deformation precedes a large earthquake, tide gauge records would be useful for earthquake prediction, so improvements in the observation system are desirable.
Simultaneous measurement of UV radiation received by the biosphere and total ozone amount
Authors: Stamnes K. , Henriksen K. , Østensen P.
Published: February 2008

We have made ground‐based measurements of solar ultraviolet (UV) irradiance with a double monochromator. The measurements are calibrated in absolute units and used to evaluate the temporal and spectral variation of the UV radiation received at the ground. We derive the column density of atmospheric ozone by fitting calculated UV irradiances to the measurements, and show that it is in basic agreement with the ozone amount inferred by a nearby Dobson spectrometer. We have thus demonstrated the feasibility of determining atmospheric ozone abundances and spectral ultraviolet irradiances simultaneously with a UV sensitive spectrometer and thereby providing the missing link between stratospheric ozone content and UV radiation received at the ground. In view of the present concerns about potential ozone depletions and related increases in UV radiation reaching the biosphere, we suggest that this procedure be used in the future to monitor the relation between atmospheric ozone amounts and UV radiation transmitted through the atmosphere. We also suggest that a combination of UV measurements and appropriate radiative transfer modeling be used to assess the effects of other environmental parameters such as clouds, aerosols, and ground albedo on the transmitted UV irradiance and to estimate the amount of UV radiation penetrating into the ocean.
Determination of rock type on Mercury and the Moon through remote sensing in the thermal infrared
Authors: Tyler Ann L. , Kozlowski Richard W. H. , Lebofsky Larry A.
Published: February 2008

Thermal infrared emission spectra of the Moon and Mercury have been obtained using the Si:As photoconductor and circular variable filter (CVF) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Lunar spectra from 7.2 µm to 12.2 µm for two different locations in the south polar highlands have Christiansen frequency peaks at 8.1 µm and 7.9 µm respectively. This indicates different compositions at the two locations; mafic in the first case, more felsic in the second. Emission spectra from Mercury are not as spatially localized; however the longitude of maximum contribution to the spectrum can be calculated from thermal models of the earth‐facing disk. Results for areas centered at two longitudes have been obtained so far. Two locations in the intercrater plains were observed. At 40° longitude (very near the crater Homer), a peak at 7.9 µm indicates mafic igneous rock type. One day later, spectra emanating from 46° longitude have peaks at 7.8 µm and indicate a region borderline between mafic and intermediate composition.
Influence of polar stratospheric clouds on the depletion of Antarctic ozone
Authors: Salawitch Ross J. , Wofsy Steven C. , McElroy Michael B.
Published: February 2008

Precipitation of nitrate in polar stratospheric clouds (PSCs) can provide a significant sink for Antarctic stratospheric odd nitrogen. It is argued that the depth of the Ozone Hole is sensitive to the occurrence of temperatures below about 196 K. An increase in the prevalence of temperatures below 196 K would enhance ozone loss by increasing the spatial extent and persistence of PSCs, and by decreasing the level of HNO3 that remains following PSC evaporation. Concentrations of halogen gases in the 1960s and earlier were insufficient to support major ozone loss, even if thermal conditions were favorable.
A prediction for Neptune's exospheric temperature
Authors: Curtis Steven Andrew
Published: February 2008

We argue that if the magnetic field of Neptune does not possess a tilt and offset similar to that of the Uranus magnetic field, then the Neptune magnetosphere will lack what may be a major source of precipitation as compared to Uranus. Limited to auroral energy inputs alone, the Neptune exosphere may be much colder. Specifically, we expect the exospheric temperature at Neptune to be about 200° K as compared to nearly 800° K at Uranus. It is also suggested that the high exospheric temperatures, which also have been observed in association with electroglow on Jupiter, Saturn and Uranus are a necessary condition for the occurrence of electroglow on Neptune. Implications of this work for the existence of Neptune electroglow are discussed.
Tomographic image of the Juan de Fuca Plate beneath Washington and western Oregon using teleseismic P‐wave travel times
Authors: Rasmussen John , Humphreys Eugene
Published: February 2008

Backprojection tomography is applied to teleseismic P‐wave travel‐time residuals to produce a detailed image of the upper mantle beneath Washington and western Oregon. Beneath the Cascades volcanic arc from central Oregon to central Washington the subducted Juan de Fuca plate is imaged as a high‐velocity quasi‐planar feature dipping ∼65°E. Resolution analysis shows that beneath southern Washington, where resolution is best, the steeply dipping slab extends to a depth of only about 300 km. The slab may end near this depth, or low‐velocity structure in the vicinity of the slab or a shallowing of the slab dip may produce this result. Beneath Oregon, where resolution is poor, the slab extends steeply into the mantle to at least 150 km depth. The uppermost mantle beneath northeastern Washington is high in velocity, preventing the resolution of the slab geometry there.
Are atmospheric “greenhouse” effects apparent in the climatic record of the contiguous U.S. (1895‐1987)?
Authors: Hanson Kirby , Maul George A. , Karl Thomas R.
Published: February 2008

The temperature and precipitation climate records for the United States have been examined. These records consist of area‐averages across the contiguous United States and northern plains. They are based on as many as 6,000 stations. Time series of these data were tested for constancy of the mean using the Spearman rank test and two‐phase regression. Test results indicate that overall trends are near zero. The only evidence for a long‐term trend is in Fall precipitation for the contiguous United States. This trend appears to result from higher fall precipitation during the period 1970‐1987 compared to the remainder of the period (1895‐1969).
Review of the reaction of O+with H2O and its bearing on composition measurements from the space shuttle
Authors: Heninger M. , Fenistein S. , Mauclaire G. , Marx R. , Murad Edmond
Published: February 2008

The rate of reaction of ground state O+with H2O has been measured in the energy range, ECM, 0.03–11 eV. The measurements show that the rate coefficient does not decrease drastically with increasing energy, contrary to previous work. The rate constant measured here is then applied to a simple model, which includes reactions of O+with water dimers, to calculate water concentration in the vicinity of the Space Shuttle. The results suggest that the pressure of water vapor may be lower than previously thought, with an upper limit of 1 × 109molecules cm−3.
Jupiter's radiation belt ions: A comparison of theory and observation
Authors: Summers Danny , Thorne Richard M. , Mei Yi
Published: February 2008

We construct radial profiles for the Jovian radiation belt flux‐tube content Y* from the reported phase‐space density of energetic particles obtained from the Voyager 1 LECP data over the range L = 6 to L = 9. These experimental profiles are compared with theoretical solutions for Y* from our interchange‐diffusion model of the coupled radiation belt and Iogenic ion populations, which incorporates the pressure gradient of the radiation belt ions and spatially‐varying forms for the precipitation loss‐rate of the radiation belt ions and the concomitant height‐integrated Pedersen ionospheric conductivity. Subject to certain limitations of the Voyager 1 data, the model solutions are found to be consistent with the data for a variety of input parameters. Model solutions are also found corresponding to radiation belt ions in the energy range 1 (MeV/G) ≤ µ ≤ 10(MeV/G) (which was not sampled by Voyager) that are expected to be mainly responsible for the auroral energy input. Comparison of our theoretical profiles with the data implies that the energetic radiation belt ions should have a peak loss rate within a factor of three of that for strong diffusion scattering.
Loss of water from Phobos
Authors: Fanale Fraser P. , Salvail James R.
Published: February 2008

A quantitative model of the migrational history of any free water in the martian satellite Phobos is presented. Results include predicted depths of retained ice and current water fluxes as a function of latitude, regolith porosity and effective pore size. It is found that, despite Phobos’ small size, low albedo and proximity to the sun, ice may be present within the sounding depth of the GRUNT experiment on the Soviet Phobos Mission—at least at mid to high latitudes. Implications for other experiments on the Phobos mission are also discussed.
Photodissociation of CO in the thermosphere of Venus
Authors: Fox J. L. , Black J. H.
Published: February 2008

Recent investigations of CO photoabsorption demonstrate that photodissociation longward of the ionization threshold at 88.5 nm occurs primarily through line absorptions rather than continuous processes. We have constructed high resolution photoabsorption cross sections for CO at rotational temperatures near 250 K from the improved data on dissociating transitions. We examine the effects of the new cross sections on the rate of solar photodissociation of CO in the thermosphere of Venus and compare the results to values obtained with the lower resolution cross sections available previously. We find that the photodissociation profile peaks slightly higher in the atmosphere and the peak value and integrated total rate both decrease by about a factor of two.
Determination of regional sources of aerosol black carbon in the Arctic
Authors: Kahl Jonathan D. , Hansen A. D. A.
Published: February 2008

Black carbon aerosol (BC), a strong absorber of visible light, constitutes a small but significant fraction of the effluent arising from carbonaceous fuel combustion processes. Estimates of the source strengths and geographical distribution of BC emissions, needed to model their effects on radiative transfer, are currently unavailable. In this letter we present a methodology for estimating regional emissions of BC in Arctic latitudes based on the synthesis of three independent pieces of information: time‐resolved measurements of BC and CO2 at Pt. Barrow, Alaska; long‐range atmospheric trajectory analyses; and tabulated values of regional fuel consumption. From a limited data base we obtain an example result indicating annual BC emissions in the Novaya Zemlya/Taymyr Peninsula regions of the northern U.S.S.R. on the order of 108 g yr−1.
Infrared absorption coefficients of gaseous chlorine nitrate at 296 K
Authors: Tuazon Ernesto C. , Wallington Timothy J.
Published: February 2008

Peak and integrated absorption coefficients of the ν1, ν2, ν3, and ν4, fundamental bands of chlorine nitrate were measured at resolutions of 0.13 cm−1 and 0.70 cm−1 for both pure and pressure‐broadened samples at 296 K. The results are compared to previous literature data.
Observational evidence for diffracted SV in the shadow of the Earth's core
Authors: Vinnik Lev P. , Farra Veronique , Romanowicz Barbara
Published: February 2008

On the basis of observational evidence, it has been assumed for a long time in the seismological literature that the diffracted S wave in the deep shadow of the earth's core is polarized as SH, in good agreement with models that do not contain a well pronounced low velocity zone at the base of the mantle. While this seems often to be the case, broad band horizontal records from the GEOSCOPE network show that, for some wavepaths, the diffracted SV is strong enough to be clearly observed at distances between 107° and 117°. Moreover, in some cases, the diffracted SV is shifted with respect to SH by approximately a quarter period. Such observations should put additional constraints on the structure near the core‐mantle boundary. Among other possibilities, lateral variations of the gradient at the base of the mantle, allowing for regions with negative gradient, and possibly azimuthal anisotropy in D″, should be considered in order to explain these data.
Variations in effective compensation depth across Aphrodite Terra, Venus
Authors: Herrick Robert R. , Bills Bruce G. , Hall Stuart A.
Published: February 2008

Aphrodite Terra is the largest elevated terrain on Venus and it serves as a focal point in current discussions of global tectonic style. Using the topography and gravity data acquired by the Pioneer Venus Orbiter (PVO) we have estimated an effective depth of Airy compensation for each of 75 orbital arcs that provide fairly uniform areal coverage of the entire province. The most pronounced pattern that emerges is a general increase in compensation depth to the east. The most rapid change occurs near 135°; the average west of there is 70 km, while the average to the east is 230 km. Superimposed on this larger trend are five distinctive regional patterns, four well defined peaks and one interval of widely scattered and poorly constrained depths. The maxima in compensation depth are well correlated with regional topographic highs. While these observations are easily reconciled with the general notion that Aphrodite is a region of crustal divergence, the great depth of compensation is difficult to accord with the more specific suggestion that Aphrodite is a terrestrial type divergent plate margin. The alternative suggestion that Aphrodite, and the other equatorial highlands on Venus, are surface manifestations of hot, upwelling mantle plumes is consistent both with the great depths of compensation and with the pattern of regional peaks and intervening troughs. The broader scale increase in effective depth of compensation from west to east is more enigmatic, but it might reflect an age progression of the plumes.
D.C. electric field stabilization of plasma fluctuations due to a velocity shear in the parallel ion flow
Authors: Ganguli G. , Lee Y. C. , Palmadesso P. J. , Ossakow S. L.
Published: February 2008

Observations from the DE 2 satellite indicate the existence of a broadband turbulence associated with sheared ion flows. A recent attempt [Basu and Coppi, 1988, 1989] to explain the observed spectrum by electrostatic waves that are driven by a sheared ion flow along the magnetic field ignores the stronger shear in the ion flow transverse to the magnetic field. We show that when the shear in the transverse ion flow is also considered the modes described by Basu and Coppi [1988, 1989] are easily stabilized and their theory breaks down even when the shear in the parallel flow exceeds the shear in the transverse flow. Hence, the explanation of the DE 2 observations based on these modes is questionable.
The effect of mass loading on the temperature of a flowing plasma
Authors: Linker Jon A. , Kivelson Margaret G. , Walker Raymond J.
Published: February 2008

We have investigated how the addition of ions at rest (mass loading) affects the temperature of a flowing plasma in a magnetohydrodynamic (MHD) approximation, using analytic theory and time dependent, three‐dimensional MHD simulations of plasma flow past Io. The MHD equations show that the temperature can increase or decrease relative to the background, depending on the local sonic Mach number (MS) of the flow. For flows with MS > √9/5 ( when γ = 5/3), mass loading increases the plasma temperature. However, the simulations show a non‐linear response to the addition of mass. If the mass loading rate is large enough, the temperature increase may be smaller than expected, or the temperature may actually decrease, because a large mass loading rate slows the flow and decreases the thermal energy of the newly created plasma.
Balloon borne observations of PSCs, frost point, ozone and nitric acid in the North Polar Vortex
Authors: Rosen James M. , Oltmans S. J. , Evans W. F.
Published: February 2008

A new balloon borne instrument called a backscattersonde has been used to study Polar Stratospheric Clouds (PSCs) at Alert, NWT (82°N, 61.5°W) during January and February of 1989. These measurements were supplemented with frost point, ozone and nitric acid vapor soundings. Type I PSCs were observed at temperatures and pressures generally consistent with present vapor pressure models of HNO3/H2O condensate, but some noticeable inconsistencies exist. It is suggested that these apparent problems, as well as some characteristic peculiarities in the PSC profiles, could be explained by the presence of two phases of the HNO3/H2O condensate.
Generation mechanism of whistler waves produced by electron beam injection in space
Authors: Pritchett P. L. , Karimabadi H. , Omidi N.
Published: February 2008

Electromagnetic particle simulations are used to determine the generation mechanism of the whistler waves observed in connection with the artificial injection of electron beams in the ionosphere. The production of the waves is shown to be closely connected with the beam‐plasma interaction, which leads to the formation of a current structure which acts like an antenna and emits the whistler waves in a coherent manner. This process, in contrast to a mechanism involving amplification of radiation by a whistler mode plasma instability within the beam, allows the whistlers to be generated even though the beam width is less than one wavelength.
Stratospheric aerosols from CH4 photochemistry on Neptune
Authors: Romani Paul. N. , Atreya Sushil K.
Published: February 2008

We have used a combined photochemical‐condensation model to study hydrocarbon ices produced from CH4 photolysis in the stratosphere of Neptune. We predict a total stratospheric haze production rate of 4.2 × 10−15 grams cm−2s−1 (75% ethane, 25% acetylene, trace diacetylene). The total production rate is insensitive to within a factor of two to order of magnitude changes in the eddy diffusion coefficient and methane mixing ratio, which is within our estimate of uncertainty for this number. The condensation temperatures are 97 K for C4H2, 71 K for C2H2, and 64 K for C2H6. Voyager 2 images of Neptune will be able to confirm the presence of stratospheric aerosols and provide constraints on their production rate and location.
Triton: Stratospheric molecules and organic sediments
Authors: Thompson W. Reid , Singh Sushil K. , Khare B. N. , Sagan Carl
Published: February 2008

Hydrocarbons and nitriles are produced in Triton's stratosphere by energetic electrons from Neptune's magnetosphere and other charged particle sources. Laboratory plasma experiments reported here show a substantial yield of molecules from low‐pressure flows of 10−3 CH4 in N2 appropriate to Triton if both CH4 and N2 are saturated at the surface. An active magnetosphere similar to that of Uranus would result in a flux ∼ 0.3 erg cm−2 s−1 of 0.1–1 MeV electrons in Triton's stratosphere; molecular production rates are then 106‐108 cm−2s−1 for NH3, C2H2, HCN, and NCCN; tens to hundreds of gm cm−2 of these compounds per 109 yr (and lesser quantities of at least eight other molecules experimentally detected) would freeze to fine‐grained white condensates in the lower stratosphere and sediment to the surface. Along with dark/colored organic haze produced in the stratosphere and other heteropolymers produced at the surface, these condensates are subject to redistribution by aeolian processes and may appear as lag deposits and/or sediment layers. A simple eddy diffusion model indicates abundances ∼ 1019 molec cm−2 for HCN and C2H2, and > 1017 molec cm−2 for NCCN, CH3CCH, CH2CCH2, and CH3CN in the stratosphere; these and other organic molecules will be detectable by IRIS if the stratosphere is (as expected) heated through ultraviolet and visible light absorption by the haze.
Generalized approach to linearized inversion with constraints
Authors: Carrion Philip M. , de Jesus Carneiro Donizeti
Published: February 2008

In this paper, we will develop a novel formalism for the generalized linear least‐squares inversion with arbitrary a priori information incorporated in the inversion in terms of “soft” and “hard” bounds. The technique can be a valuable tool for solving different problems, including those related to global seismology and high‐resolution crustal imagery, especially when numerical algorithms break down due to the absence of properly chosen constraints. Due to different undesirable events in the recorded data (such as leg jumps, skips, significant noise level) the conventional least‐squares in realistic situations can give erroneous solutions since the model parameters can easily readjust to variations in the measured data and give inaccurate or even non‐physical results. Constrained inversion has been overlooked by geophysicists since the mathematics involved are much more complicated. We show that using the concept of duality, constrained problems can be transformed to unconstrained dual problems and an explicit solution with soft and hard bounds can be found.
Hydration and dehydration of Zeolitic Tuff from Yucca Mountain, Nevada
Authors: Kranz R. L. , Bish D. L. , Blacic J. D.
Published: February 2008

Naturally occurring zeolites expand and contract when hydrated or dehydrated. In tuffaceous rock composed largely of such zeolites, the entire rock may swell or contract significantly as the rock becomes saturated or dries out. If such rock is constrained, significant stresses may develop as a result of hydration or dehydration. We present experimental results that substantiate this. In a zeolitized, non‐welded tuff from Yucca Mountain, NV, rock permeability governs the swelling rate since the major constituent, clinoptilolite, hydrates as fast as it can be exposed to water. At Yucca Mountain, where a nuclear waste repository is proposed, strata of welded, devitrified tuff overlie non‐welded, zeolitic tuff. Should the hydration state of the units change significantly over the repository lifetime, additional stresses on the same order of magnitude as now exist may develop.
Relativistic electrons at geosynchronous orbit, interplanetary electron flux, and the 13‐month Jovian synodic year
Authors: Christon S. P. , Chenette D. L. , Baker D. N. , Moses D.
Published: February 2008

We report the results of a search to determine the correlation, if any, between the temporal behaviors of ≳ 0.2‐7 MeV electrons at geosynchronous orbit (∼6.6 Re) and 6‐10 MeV electrons in the interplanetary region near Earth at the period of the jovian synodic year (∼13 months). The ∼13‐month intensity variation results from the synodic interplanetary magnetic field connection of Earth to Jupiter. Direct comparison of intensity‐time flux profiles for the years 1976‐1984, ∼7 synodic jovian electron seasons, shows that the intensity envelope of peak electron flux at ∼6.6 Re6 does not appear to be correlated to the observed ∼13‐month intensity envelope of relativistic electron flux in the interplanetary region near Earth. A persistent ∼13‐month variation of geosynchronous orbit flux is not obvious, thus indicating that the intensity of electron flux at ‐6.6 Re is not directly and solely related to the intensity of jovian electron flux near Earth. We conclude that dynamic energization and redistribution processes in Earth‧s magnetosphere must be invoked to produce the intensity variations of relativistic electron flux at ∼6.6 Re and not interplanetary magnetic field connection to Jupiter.
Linear properties of eddies in a Jovian troposphere forced by deep jets
Authors: Orsolini Y. , Leovy C. B.
Published: February 2008

We use a linear quasi‐geostrophic β‐plane model to study large‐scale instabilities of the Jovian upper troposphere forced from below by zonal jets. The jets are presumed to be barotropically stable in the isentropic deep interior, but barotropically unstable in the statically stable upper troposphere. We explore the effect on this barotropic instability of weak vertical shear causing the jets to decay with height and find: (1) eastward jets are stabilized by weaker shear than westward jets, (2) the most unstable eddies are strongly confined by the shear, (3) eddy fluxes contribute to vertical decay of the jets, (4) the lower residual mean meridional circulation cells exhibit rising motion in regions of anticyclonic shear, but these are overlain by reverse cells.
Predicted compositions for high‐density hydrous magnesium silicates
Authors: Finger L. W. , Prewitt C. T.
Published: February 2008

Recent studies of high‐pressure hydrous magnesium silicates have revealed a wide variation of structures and chemistries. These materials are composed of layers of octahedra that have “rock‐salt” topology modified by vacancies and silicon replacing magnesium, and by layers with octahedral magnesium, tetrahedral silicon and olivine‐humite series stoichiometry. There are two ways to form a close‐packed oxygen substructure from these types of layers. One scheme has a 1∶1 ratio of the two layers and a four‐unit or 9.4Å repeat. The second stacking sequence has two olivine‐series layers for each octahedral unit and a six‐layer or 14Å repeat. A general formula for the compositions of these phases is , where mod(n,2) is the remainder when n is divided by 2; n = 1,2,3,4, ∞; and m = 1,2, ∞. This formula has been used to predict compositions and room pressure‐temperature densities. These phases have mixed tetrahedral and octahedral coordination for silicon and could be important constituents of the mantle transition zone.
Evolution of an unstable shell distribution of pickup cometary ions
Authors: Yoon Peter H. , Mandt M. E. , Wu C. S.
Published: February 2008

It has been established in recent years based on theoretical discussions and observations that the solar wind can pick up newborn cometary ions, and the pickup ions usually form a shell distribution. A relevant question is what can subsequently happen to such a distribution. To address this problem, two publications have discussed the linear stability of the shell distribution [Freund and Wu, 1988; Gary and Sinha, 1989]. In the present discussion, both the linear and nonlinear development of the waves and the evolution of the initial shell distribution are investigated by numerical simulations. For this purpose, the linear theory is also generalized so that some additional important effects are incorporated.
ER‐2 mountain wave encounter over Antarctica: Evidence for blocking
Authors: Bacmeister Julio T. , Schoeberl Mark R. , Lait Leslie R. , Newman Paul A. , Gary Bruce
Published: February 2008

A three dimensional linear model of orographically forced gravity waves (mountain waves) using realistic topography is used to simulate a high altitude (20 km) ER‐2 encounter with a large mountain wave over Alexander Island (72° W, 69° −72° S). Reasonable agreement between the linear model and observations is obtained if the effects of low‐level flow blocking are taken into account.
The extended tracking network and indications of baseline precision and accuracy in the north Andes
Authors: Freymueller Jeffrey T. , Kellogg James N.
Published: February 2008

The CASA UNO Global Positioning System (GPS) experiment (January‐February 1988) included an extended tracking network which covered three continents in addition to the network of scientific interest in Central and South America. The repeatability of long baselines (400–1000 km) in South America is improved by up to a factor of two in the horizontal vector baseline components by using tracking stations in the Pacific and Europe to supplement stations in North America. In every case but one, the differences between the mean solutions obtained using different tracking networks was equal to or smaller than day‐to‐day rms repeatabilities for the same baselines. The mean solutions obtained by using tracking stations in North America and the Pacific agreed at the 2–3 millimeter level with those using tracking stations in North America and Europe. The agreement of the extended tracking network solutions suggests that a broad distribution of tracking stations provides better geometric constraints on the satellite orbits and that solutions are not sensitive to changes in tracking network configuration when an extended network is used. A comparison of the results from the North Andes and a baseline in North America suggests that the use of a geometrically strong extended tracking network is most important when the network of interest is far from North America.
Aerosol nucleation in the winter Arctic and Antarctic stratospheres
Authors: Hamill Patrick , Toon O. B. , Turco R. P.
Published: February 2008

We calculate the formation rate of sulfuric acid ‐ water aerosol particles as a function of altitude for the conditions of the winter Arctic and Antarctic stratospheres. The theoretical results indicate that sulfate particle formation can occur in the polar winter stratosphere. Conditions for new particle formation are increasingly favorable as the altitude increases between 20 and 30 km because of the decrease in surface area of pre‐existing particles and increasing sulfuric acid vapor supply. The theoretical predictions are consistent with observations of a high altitude CN layer over Antarctica in the spring. Available vapor pressure data indicate that ternary system particles composed of sulfuric acid, nitric acid and water are not thermodynamically stable under winter stratospheric conditions.
Incorporation of stratospheric acids into water ice
Authors: Elliott Scott , Turco Richard P. , Toon Owen B. , Hamill Patrick
Published: February 2008

Hydrochloric and hydrofluoric acids are absorbed within the water ice lattice at mole fractions maximizing below 10−5 and 10−4 in a variety of solid impurity studies. The absorption mechanism may be substitutional or interstitial, leading in either case to a weak permeation of stratospheric ices by the acids at equilibrium. Impurities could also inhabit grain boundaries, and the acid content of atmospheric ice crystals will then depend on details of their surface and internal microstructures. Limited evidence indicates similar properties for the absorption of HNO3. Water ice lattices saturated with acid cannot be a significant local reservoir for HCl in the polar stratosphere.
Condensation of HNO3 on falling ice particles: Mechanism for denitrification of the polar stratosphere
Authors: Wofsy S. C. , Salawitch R. J. , Yatteau J. H. , McElroy M. B. , Gandrud B. W. , Dye J. E. , Baumgardner D.
Published: February 2008

Ice particles created in polar stratospheric cooling events are predicted to descend into Type I PSCs and accrete a coating of nitric acid trihydrate (NAT) that inhibits evaporation. Coated particles efficiently strip HNO3 from the atmosphere, providing a mechanism for denitrification without significant dehydration. Coatings that disintegrate may release large particles of NAT that influence subsequent particle growth.
Stratospheric constituent trends from ER‐2 profile data
Authors: Schoeberl Mark R. , Proffitt Michael H. , Kelly Ken K. , Lait Leslie R. , Newman Paul A. , Rosenfield Joan E. , Loewenstein Max , Podolske Jim R. , Strahan Susan E. , Chan K. Roland
Published: February 2008

Trend analysis of the AASE ER‐2 profile data reveals an average decrease in N2O on potential temperature isentropes which can be attributed to diabatic cooling of inner vortex air. This conclusion is independently supported by radiative transfer computations. Trends in ozone and water vapor over the same period are not consistent with the magnitude of the diabatic descent. After accounting for the diabatic motion (estimated from N2O) an additional 0.44±.3%/day average anomalous O3 decrease above 440K (∼20 km) is needed to balance the continuity equation. This ozone decrease suggests additional photochemical destruction of ozone in the presence of the high amounts of ClO observed during the mission. A 0.4±0.3%/day average anomalous increase in H2O is also observed near 420K (∼18 km) which may be due to the evaporation of ice crystals falling from higher, colder stratospheric layers.
Reconstruction of O3 and N2O fields from ER‐2, DC‐8, and balloon observations
Authors: Lait Leslie R. , Schoeberl Mark R. , Newman Paul A. , Proffitt Michael H. , Loewenstein Max , Podolske Jim R. , Strahan Susan E. , Chan K. Roland , Gary Bruce , Margitan James J. , Browell Edward , McCormick M. Patrick , Torres Arnold
Published: February 2008

Measurements of N2O and O3 during the Airborne Arctic Stratospheric Expedition have been composited using the potential vorticity and potential temperatire of each measurement as coordinates. For ozone, data sources included the ER‐2 and balloon ozonesonde in situ measurements, DC‐8 DIAL lidar, and SAGE satellite profiles. For N2O, only ER‐2 data were used. These chemical composites have been reconstructed onto average meteorological fields for the mission in a latitude‐altitude cross‐section, yielding a picture of the chemical composition of the polar vortex during this period. Tracers inside the vortex show an apparent descent of about 2 km relative to those outside, resulting in an apparent chemical edge on isentropic and isobaric surfaces.
Global three‐dimensional constituent fields derived from profile data
Authors: Douglass Anne R. , Rood Richard B. , Stolarski Richard S. , Schoeberl Mark R. , Proffitt Michael H. , Margitan James J. , Loewenstein Max , Podolske James R. , Strahan Susan E.
Published: February 2008

The success of 3D simulations of stratospheric constituent variability depends critically on the initialization of the constituent fields within the global model. We describe a technique for generating global 3D fields from vertical constituent profiles. The technique uses potential vorticity (q) and potential temperature (θ) to map the profiles onto the global domain. The profiles used here are obtained from a 2D model calculation that reproduces the relationship between θ, q, N2O and O3 observed during the Airborne Arctic Stratospheric Expedition (AASE). The method is verified by comparison with satellite data, aircraft data and model simulations.
Studies of Arctic stratospheric ozone in a 2‐D model including some effects of zonal asymmetries
Authors: Isaksen I. S. A. , Rognerud B. , Stordal F. , Coffey M. T. , Mankin W. G.
Published: February 2008

A two‐dimensional (2‐D) zonally averaged chemistry‐transport model of the stratosphere has been extended to include some zonally asymmetric effects to study the chemically disturbed conditions in the Arctic winter during the occurrence of polar stratospheric clouds (PSCs). The model allows air parcels that have been in PSCs in the polar night to be exposed to sunlight during the passage south through a wave trough. Large enhancements of ClO are estimated as well as significant ozone reductions, most pronounced around the 20 km height level. The ozone depletions maximize in late March, about one month after the cease in PSC activity in the model, and amount to 5–8% in column ozone at 70°N. In agreement with column measurements made from the DC‐8, the model estimates an increase in the columns of HNO3 and ClCNO2, and a decrease in the HCl column within the polar vortex.
Solar wind properties observed during high‐latitude impulsive perturbation events
Authors: Bering Edgar A. , Lanzerotti Louis J. , Benbrook James R. , Lin Z.‐M. , Maclennan Carol G. , Wolfe Allan , Lopez Ramon E. , Friis‐Christensen Eigil
Published: February 2008

The data base from the 1985–86 Balloon Campaign at South Pole Station, Antarctica, has been searched for impulsive magnetic and electric field events that occurred when IMP 8 was in the solar wind and data were acquired. Two events are shown that appear to be similar to published examples of high latitude “twin vortex” current systems. Neither event was preceded by a dynamic pressure pulse in the solar wind. These examples disprove the hypothesis that all such high‐latitude impulses arise solely from dynamic pressure pulses produced by the solar wind. Further, on a statistical basis, a total of 42 events were found for which IMP 8 data are available. Of these events, 12 occurred when the ZGSM component (BZ) of the interplanetary magnetic field (IMF) was northward and 30 occurred when BZ was southward. Only 3 of the BZ north cases and only 5 of the BZ south cases were preceded by pressure pulses greater than 0.4 nPa in amplitude.
Magnetic field configuration of the Theta aurora
Authors: Toffoletto F. R. , Hill T. W.
Published: February 2008

The theta aurora is an approximately Sun‐aligned transpolar arc that often extends the entire length of the polar cap, linking the dayside and nightside auroral zones. It is a remarkable manifestation of polar cap auroral activity that appears during periods of northward interplanetary magnetic field (IMF). In this paper we describe a magnetic configuration of the open magnetosphere that is conducive to the formation of the theta aurora when the IMF has a significant northward component. We present a magnetic field topology and polar cap configuration that is derived from a quantitative model of the open magnetosphere that incorporates Crooker's antiparallel merging hypothesis. Under this hypothesis, when the IMF has a northward component, the dayside merging line bifurcates, leaving a large fraction of the subsolar magnetopause untouched by the merging process. The polar cap, defined by tracing magnetic field lines that connect from the solar wind to the Earth, is similarly bifurcated, leaving a sun‐aligned stagnation region that is not magnetically connected to the solar wind and may plausibly be associated with the sun‐aligned “bar” of the theta aurora. The model provides testable predictions with regard to the position of this “convection gap” in both northern and southern hemispheres as functions of IMF direction.
High‐frequency waves following PKP‐CDIFF at distances greater than 155°
Authors: Nakanishi Ichiro
Published: February 2008

Using a seismic network in Hokkaido‐Tohoku region, Japan we observe PKP waves in the distance range 152 to 157°from a deep earthquake in Argentina. The seismic network consists of 26 stations and provides us with a data set of dense distance sampling. The examination of amplitude variation of PKP‐BC and PKP‐Cdiff with distance locates the C‐cusp at about 155.5° for a surface source for the path from Argentina to Japan. This C‐cusp position suggests a P velocity of 10.27 km/s at the bottom of the outer core. The bandpass filtering of the data shows that high‐frequency waves are observed following PKP‐Cdiff at distances beyond the C‐cusp. The waves are characterized by a dominant frequency of about 2 to 3 Hz, a long duration of oscillation until the arrival of PKP‐AB, and an apparent onset slowness of about 4 s/deg, which is approximately equal to that of PKP‐AB in the distance range. The onset time of the high‐frequency waves seems to be consistent with the least time of the scattering of PKP‐BC on the receiver side near the bottom of the upper mantle.
Chemical bonding and the incorporation of potassium into the Earth's core
Authors: Sherman David M.
Published: February 2008

It has been argued that most of the Earth's potassium was segregated into the outer core and that the radioactive decay of 40K provided the heat source for the geodynamo. This idea rests on the assumption that the affinity of potassium for sulfur or metallic iron is enhanced at high pressure. In this paper, the high pressure electronic structures of K in sulfide, iron sulfide and metallic iron coordination environments were determined from molecular orbital (SCF‐Xα‐SW) calculations on (KS8)15−, (KS8Fe6)3− and KFe14 clusters. It is shown that, even at high pressure, potassium cannot alloy with metallic iron. Although a high‐pressure electronic transition may enhance the potassium‐sulfur chemical bond, the electronic structure of the KS8Fe6 cluster shows that this electronic transition cannot happen in an iron sulfide melt. Consequently, potassium will not have an enhanced affinity for sulfur in planetary interiors. If the lower mantle were more reducing, potassium might be excluded from the silicate phases by more strongly lithophile elements and segregated into a metal sulfide phase in the outer core (cf. the phase assemblages in enstatite chondrites). Given the oxidation state of the Earth, however, it is unlikely that significant quantities of potassium have been incorporated into the outer core. The Earth, like the moon and the eucrite parent body, is depleted in potassium. An alternative heat source (e.g., the radioactive decay of U and Th) must be invoked to explain the geodynamo.
Photodissociation of Cl2O2 in the Spring Antarctic lower stratosphere
Authors: Eberstein Igor J.
Published: February 2008

The likely photodissociation pathways of chlorine peroxide are examined. Reasoning by analogy between hydrogen peroxide and chlorine peroxide, it is shown that photodissociation of chlorine peroxide at wavelengths longer than 250 nm is not likely to give chlorine atoms as a primary product. Reasoning by analogy with molecules whose visible spectra are known, it is concluded that chlorine peroxide is also likely to photodissociate in the visible to give ClO radicals as primary products.