bluuebunny/crossref_metadata_2025 huggingface dataset:
Diurnal variation of nitric oxide at 26 km
Authors: Kondo Y. , Iwata A. , Pirre M. , Ramaroson R. , Delannoy C. , Matthews W. A. , Koike M. , Suzuki K.
Published: February 2008

A chemiluminescent NO detector was launched from Uchinoura, Japan (31°N), at 0030 JST on July 29, 1987. The balloon reached a float altitude of 26 km at around 0200 JST and stayed at this altitude until 1600 JST when it started a slow descent. Near local sunrise, when the solar zenith angle reached 92.7°, the NO concentration started to increase rapidly. This rapid increase continued for about 30 minutes. The NO concentration continued to increase, albeit more slowly, for a further 7 to 8 hours, and then became stable. The NO diurnal variation is calculated by a time‐dependent photochemical model assuming a 14 ppbv total odd nitrogen concentration, constrained by ozone and temperature measured simultaneously with NO; the result agrees quite well with the observed temporal NO variation. The observed slow increase in NO can quantitatively be explained by the photodissociation of N2O5. The N2O5 concentration just before sunset is estimated to be 1.9±0.4 ppbv at 26 km.
Single station ocean current vector measurement: Application of the Spaced Antenna (SA) Technique
Authors: May Peter T. , Weber Bob L. , Strauch Richard G. , Lataitis Richard J. , Moran Kenneth P. , Merritt David A.
Published: February 2008

The Spaced Antenna (SA) technique is applied to measuring ocean surface currents for the first time. This allows the measurement of the ocean surface current transverse to the radar beam as well as the radial current and thus eliminates the requirement of two separate radars to measure the full current vector as with present ocean surface current radar systems. Therefore, this technique offers considerable advantages for ocean current mapping in terms of simplicity for real‐time operational systems and could have wide applications, for example at sites where it is not practical to have two separate radars.
The horizontally lying slab
Authors: Okino Kyoko , Ando Masataka , Kaneshima Satoshi , Hirahara Kazuro
Published: February 2008

An unusual earthquake (mb=6.2) occurred in the Izu‐Bonin Island region in July 1982. The event, occurring at a depth of 545 km, was clearly separated from the main inclined seismic zone by a distance of about 200 km. To diagnose the situation, we have considered two possibilities: 1) the event might be an unusual event in the sense that its location is unrelated to the position of the subducted slab and that there is probably no slab around it, or 2) the slab, at this depth, might be lying horizontally on top of the 650 km discontinuity, and the unusual event occurred in this horizontal part. Both possibilities have been modeled structurally. We have computed the P‐wave travel times for the present event, as well as for two other events located unambiguously in the inclined part of the seismic zone by employing a 3‐D ray tracing program. The computed travel time residuals have been compared with the observations at stations in western Japan. The observations are found to be consistent with the model of the horizontally lying slab. Our result, thus, suggests that the slab might be horizontal at this depth in this part of the Izu‐Bonin Islands.
Direct injection of ionospheric O+ into the dayside low latitude boundary layer
Authors: Fuselier S. A. , Klumpar D. M. , Peterson W. K. , Shelley E. G.
Published: February 2008

Observations from the AMPTE/Charge Composition Explorer (AMPTE/CCE) indicate the presence of two distinct O+ populations in the dayside subsolar low latitude boundary layer during some periods of northward Interplanetary Magnetic Field (IMF). The first population is O+ convected into the boundary layer from the outer magnetosphere and has been reported previously. It is suggested here that the new, second, O+ population is injected into the dayside boundary layer directly from the high latitude ionosphere. This second population can have a significant density and distinct characteristics such as field‐aligned flow relative to boundary layer H+ that modify both the plasma composition and dynamics in the low latitude boundary layer.
Three Dimensions Simulation of Spatial and Temporal Variability of Stratospheric Hydrogen Chloride
Authors: Kaye Jack A. , Rood Richard B. , Allen Dale J. , Larson Edmund M. , Jackman Charles H.
Published: February 2008

Spatial and temporal variability of atmospheric HCl columns are calculated for January 1979 using a three‐dimensional chemistry‐transport model designed to provide the best possible representation of stratospheric transport. Large spatial and temporal variability of the HCl columns is shown to be correlated with lower stratospheric potential vorticity and thus to be of dynamical origin. Systematic longitudinal structure is correlated with planetary wave structure. These results can help place spatially and temporally isolated column and profile measurements in a regional and/or global perspective.
The sorption behavior of SO2 on ice at temperatures between −30°C and −5°C
Authors: Clapsaddle Craig , Lamb Dennis
Published: February 2008

Laboratory experiments explored the sorption behavior of SO2 on ice between the temperatures of −30 and −5°C and with SO2 mixing ratios of 15 to 95 ppb. The time‐dependent data show clear evidence of two distinct exponential time constants and a dependence on SO2 concentration. The equilibrium amount of SO2 retained by the ice, determined by integration of the kinetic data, was found to increase strongly with temperature. The experimental results may be interpreted in terms of a disordered surface region which increases in thickness with temperature, enlarging the storage reservoir and generating the observed temperature dependence.
Particle motion and pressure relationships of ocean bottom noise: 3900 M depth; 0.003 to 5 Hz
Authors: Barstow Noël , Sutton George H. , Carter Jerry A.
Published: February 2008

Samples of ocean bottom noise in the frequency band 0.003 to 5 Hz are analyzed for coherency and amplitude and phase relationships among pressure and the three components of particle motion. Data available from the Columbia‐Point Arena ocean bottom seismic station (38° 09.2′N, 124° 54.4′W) provide examples of different noise conditions. Coherent energy peaks near 0.14, and 0.06 Hz suggest fundamental mode Rayleigh wave motion propagating shoreward. Coherent energy near .30 Hz appears to be variable. Pressure variations near 0.01 Hz and lower frequency correlate with wave heights along the California coast and appear to produce forced deformation of the bottom.
The interiors of Pluto and Charon: Structure, composition, and implications
Authors: Simonelli Damon P. , Reynolds Ray T.
Published: February 2008

We review recent models of the internal structure of Pluto and Charon made possible by analysis of the Pluto/Charon mutual events. At a mean density of just over 2 g cm−3 and a predicted rock mass fraction of roughly 0.7, the Pluto/Charon system is significantly rockier than the icy satellites of the giant planets, a contrast which may reflect its formation in a CO‐rich outer solar nebula rather than a circumplanetary nebula. Pluto and Charon may in fact be so rocky that they lost volatiles early in their history (possibly during a Charon‐forming impact event), although this is still an open issue. Finally, we review the outlook for future study of the Pluto and Charon interiors.
Thermal expansion measurements at very high pressure, systematics, and a case for a chemically homogeneous mantle
Authors: Chopelas A. , Boehler R.
Published: February 2008

New data on thermal expansivity, α, of iron to over 400 kbar in laser‐ and electrically‐heated diamond anvil cells and on MgO and forsterite from spectroscopic data to over 200 kbar and previously measured adiabats [Boehler, 1982], imply that α at high pressure may be described by a constant value of (∂1nα/∂1nV)T = 5.5 ± 0.5. This behavior is supported by previous α measurements at lower pressures on a large variety of materials. Densities of magnesio‐wüstite and silicate perovskite in a pyrolitic ratio calculated at lower mantle conditions using a finite strain equation and α at high pressures, using the above systematics, match those in PREM through the entire lower mantle, making a strong case for a uniform mantle.
Paleomagnetism of the Hog Heaven Volcanic Field, Montana: Difficulties in averaging paleosecular variation in volcanic fields
Authors: Sheriff Steven D.
Published: February 2008

Twelve virtual geomagnetic poles from 25 paleomagnetic sites in the Oligocene Hog Heaven volcanic field of northwestern Montana yield a mean pole at 74.4°N, 71.5°E (alpha 95 = 5.9°). This pole indicates clockwise rotation of 10.5° ± 7.4° and flattening of 13.2° ± 4.6° at the 95% confidence level. Assuming the axial geocentric dipole hypothesis criteria have been satisfied, at 95% confidence rotation and flattening are statistically different from zero. These results indicate clockwise rotation of the Hog Heaven volcanic field as expected for the Sanpoil block farther west. However under these assumptions this farsided pole requires northward transport of nearly 1400 km, about 100 times too much given the geologic constraints. Thus, although radiometric dates indicate 5 million years of volcanism, several igneous rock types are present, there are interbedded sediments and erosional intervals during volcanism, and both stable states of the geomagnetic field are recorded, this pole is not a reliable estimate of the Oligocene rotation axis. Perhaps the volcanic events were not distributed independently with respect to paleosecular variation, or a long‐term nondipole field component persisted during much of the evolution of the Hog Heaven volcanic field. These results and previous studies indicate paleomagnetic data from one volcanic field may not be sufficient to estimate tilt, translation, or rotation of a tectonic block.
Effect of metals on the rate of the oxidation of H2S in seawater
Authors: Vazquez G. Felipe , Zhang Jia‐zhong , Millero Frank J.
Published: February 2008

Recent measurements on the oxidation of H2S in the Black Sea yielded rates that were ten times faster than expected. To determine if this increase was due to trace metals, measurements have been made on the oxidation of H2S in seawater with added transition metals. Below a concentration level of 100 nM, none of the metals except Fe2+ affect the rate of oxidation. At higher concentrations the rates increase for all the metals except Zn2+. The increase in the rates followed the order. The increase in the rates below sulfide precipitation appears to be related to the formation of MHS+ ion pairs that have a higher rate of oxidation than HS−. Only Fe2+ and Mn2+ have concentrations high enough to be effective in influencing the rate of oxidation of H2S in the waters of anoxic basins and sediments. The estimated rates of oxidation of H2S in the Black Sea using the laboratory measurements were found to be in reasonable agreement with the measured values. Since CuHS+ has a higher rate of oxidation than HS−, it cannot be used to explain the stability of H2S in oxic seawaters. A more likely choice is ZnHS+.
Modulations in the polar mesosphere summer echoes and associated atmospheric gravity waves
Authors: Williams P. J. S. , van Eyken A. P. , Hall C. , Röttger J.
Published: February 2008

Mesospheric observations were made by the EISCAT VHF radar. On one occasion a relatively weak Polar Mesosphere Summer Echo (PMSE) was observed with its intensity varying with a period of about 27 minutes. Immediately below the PMSE layer an atmospheric gravity wave was observed, also with a period of about 27 minutes. The maximum intensity of the PMSE corresponded to the maximum upward velocity associated with the wave. Particle precipitation, adiabatic cooling due to the upward velocity and wave steepening and breaking at the mesopause may all play a role in causing PMSEs.
Search for atmospheric holes with the Viking cameras
Authors: Frank L. A. , Sigwarth J. B. , Craven J. D.
Published: February 2008

Images taken with the two ultraviolet cameras on board the Viking spacecraft were examined for evidence of transient decreases of Earth's ultraviolet dayglow. Comparison of near‐limb observations of dayglow intensities with those at smaller angles to the nadir with the camera sensitive to OI 130.4 nm emissions supports the existence of transient decreases in the near‐nadir dayglow. However, the amount of near‐nadir imaging is severely limited and only several significant events are found. More decisive confirmation of the existence of such transient decreases must await a larger survey from another spacecraft. The diameters of these regions as detected with Viking are ∼ 50 to 100 km. Occurrence frequencies, intensity decreases, and dimensions for these clusters of darkened pixels are similar to those previously reported for such events, or ‘atmospheric holes’, as seen in images of the ultraviolet dayglow with Dynamics Explorer 1.
Equatorially generated ULF waves as a source for the turbulence associated with ion conics
Authors: Johnson Jay R. , Chang Tom , Crew G. B. , André Mats
Published: February 2008

Low frequency turbulence present on closed field lines in the central plasma sheet has been used to explain ion heating and conic formation with remarkable success. However, the source of the turbulence has yet to be established, and there are no obvious local sources which could power such a broadband spectrum. Alternatively, observations reveal that ion distributions in the equatorial region are often anisotropic, and such distributions excite both ion cyclotron waves below the proton gyrofrequency and waves near the harmonics of the hydrogen cyclotron frequency. As these waves propagate to lower altitudes where the magnetic field is stronger, their left‐hand circularly polarized component resonates with heavy ions. The presence of a parallel gradient in the magnetic field complicates the details of wave propagation so that downcoming right‐hand circularly polarized waves, which acquire a left‐hand circularly polarized component at the crossover frequency, may tunnel through a “stop zone” to altitudes where they contribute to the observed ion heating.
The Uranian magnetopause: Lessons from Earth
Authors: Russell C. T. , Song P. , Lepping R. P.
Published: February 2008

Magnetic field measurements by Voyager 2 reveal differences between the Uranian magnetopause and the typical terrestrial magnetopause. In particular there are pulsations in the magnetic field at Uranus which may represent partial crossings of the magnetopause, the entry into magnetic flux ropes or the passage through mirror mode waves. Examination of terrestrial data especially those obtained under conditions of very high plasma beta suggests that the last possibility is the more likely. The magnetopause crossing itself is also different than those typically observed at 1 AU. It contains a magnetic field rotation of over 270°. While this is rare at 1 AU, an example has been found at Earth where the field rotation is also greater than 270°. In some aspects these crossings resemble slow shocks. This also occurred at a time of high plasma beta. Thus we conclude that plasma beta is very important in determining the structure of the magnetopause.
Plasticity of MGSIO3 perovskite: The results of microhardness tests on single crystals
Authors: Karato Shun‐ichiro , Fujino Kiyoshi , Ito Eiji
Published: February 2008

The Plasticity of single crystals of MgSiO3 perovskite was studied (at room temperature) by the microhardness tests using a Vickers and a Knoop indenter. The Vickers hardness, Hv, of MgSiO3 perovskite was determined to be 18 +/− 2 GPa, about a factor of two larger than the hardness of either enstatite or olivine, indicating a significantly larger resistance to plastic flow of this mineral than that of the upper mantle minerals. The normalized hardness, Hv/μ (μ: shear modulus), of MgSiO3 perovskite is in reasonable agreement with those of titanate perovskites (SrTiO3, BaTiO3, CaTiO3), although a cubic perovskite SrTiO3 has a significantly lower hardness than others. The Knoop tests showed anisotropic hardness consistent with the slip systems
.
Twin sources of high‐frequency volcanic tremor of Izu‐Oshima Volcano, Japan
Authors: Furumoto Muneyoshi , Kunitomo Takahiro , Inoue Hiroshi , Yamada Isao , Yamaoka Koshun , Ikami Akira , Fukao Yoshio
Published: February 2008

The 1986 fissure eruption of Izu‐Oshima volcano was preceded and followed by strong volcanic tremor activities. The post‐eruption tremor activity consists of an alternating sequence of a tremor episode lasting about 10 min and the subsequent quiescence of about 40–50 min. We observed this post‐eruption activity by a 24‐channel seismic array deployed on the caldera floor. The semblance analysis of the recorded data revealed that high frequency (>5Hz) components of the tremor were radiated from two separated sources beneath the caldera. The tremor first occurred at one source and then migrated to the other source in a transition time of about a few minutes during each tremor episode. This transition suggests that the two sources are dynamically linked with each other in a magma‐filled crack or conduit.
Large stratospheric sudden warming in Antarctic late winter and shallow ozone hole in 1988
Authors: Kanzawa Hiroshi , Kawaguchi Sadao
Published: February 2008

There occurred a large stratospheric sudden warming in the southern hemisphere in late winter of 1988 which competes in suddenness and size with major mid‐winter warmings in the northern hemisphere. Associated with the dynamical phenomenon of the sudden warming, total ozone increased over the eastern hemispheric part of Antarctica. The sudden warming as well as other warmings which followed it made the 1988 Antarctic ozone hole shallow in depth and small in area.
Magnetic impulses and associated optical signatures in the dayside aurora
Authors: Mende S. B. , Rairden R. L. , Lanzerotti L. J. , Maclennan C. G.
Published: February 2008

We present five magnetic impulse events observed at South Pole and in the magnetically conjugate area at Iqaluit. The magnetic signatures recorded during these events appear to be similar to those discussed by several authors as possible ionospheric signatures of sporadic dayside reconnection via the flux transfer process. Coordinated ground‐based image‐intensified all sky camera data were acquired at South Pole during the events. The optical data show that prior to the onset of each of the events the dayside cusp aurora is several degrees poleward of the station, signifying event initiation on closed field lines. Overhead aurora appears at the onset of the magnetic event and precipitation seems to expand over a large region equatorward of the quiescent cusp aurora. As the event decays the aurora dies away and the quiescent dayside cusp aurora, in four out of five cases, returns poleward of the station. This morphology is inconsistent with the model in which the ground based signature of an FTE is caused by a field aligned current configuration moving over a ground station in the antisunward direction. The observations show temporal events which begin at or inside the boundary of closed field lines. These are consistent with sudden precipitation activity on flux tubes which were previously equatorward of the cusp/cleft boundary and which became temporarily disconnected (non‐dipolar).
Ivory coast microtektites and geomagnetic reversals
Authors: Schneider David A. , Kent Dennis V.
Published: February 2008

The reported association of the Ivory Coast microtektite occurrence with the onset of the Jaramillo normal polarity subchron has given support to the notion that impact events can give rise to geomagnetic reversals. We re‐evaluate the paleomagnetic stratigraphy of two critical deep‐sea sediment cores bearing Ivory Coast microtektites (K9‐57 and V27‐239) and show that this event likely occurred during the Jaramillo subchron approximately 30 kY after its onset and 40 kY before its termination. This new result thus argues against any causal relationship between the Ivory Coast tektite‐producing event and a geomagnetic polarity reversal.
Stratospheric cloud micro‐layers and small‐scale temperature variations in the Arctic in 1989
Authors: Hofmann D. J.
Published: February 2008

Thin layers of large (r ≈ 2–3 μm) particles were observed in the Arctic between 14 and 27 km on 23 and 30 January 1989. Although the particle mass is consistent with the available HNO3 vapor, it is not always clear whether the morphology of the layers is the result of recent condensation or evaporation as the layers appear under conditions of both supersaluration and undersaturation with respect to nitric acid trihydrate (NAT). Large amplitude, small vertical scale temperature variations appear to be associated with the layers but not in a simple manner. In regions supersaturated with respect to NAT, condensation on only a few of the available condensation nuclei takes place. Such preferential condensation into thin large particle layers suggests that this class of nuclei may be different than the previously assumed sulfate aerosol nuclei. The possibility that they may be derived from solid fuel rocket effluent and spacecraft ablation products is examined and cannot be excluded. Such a source may explain the appearance of these cloud layers at high altitude.
Turbulent polar heliospheric fields
Authors: Roberts D. A.
Published: February 2008

Recent observational studies of interplanetary field fluctuations and magnetohydrodynamic (MHD) simulation results are used to suggest that the turbulent evolution of the fields over the solar poles leads to a state intermediate between the large fields of the static limit and the small fields given by “saturation” (δB/B ≈ 1). In particular, assuming the strength of the coronal hole sources of fluctuations are similar in all solar regions, the polar fluctuations in the outer heliosphere are likely to be nearly isotropic with amplitudes somewhat smaller than those predicted by the WKB extrapolation from 1 AU in the ecliptic plane.
Current carriers in the near‐Earth cross‐tail current sheet during substorm growth phase
Authors: Mitchell D. G. , Williams D. J. , Huang C. Y. , Frank L. A. , Russell C. T.
Published: February 2008

Throughout most of the growth phase of a substorm, the cross‐tail current at x ∼ −10 Re can be supplied by the curvature drift of a bi‐directional field aligned distribution of ∼1 keV electrons. Just prior to its local disruption after substorm onset, the cross‐tail current in the now thin (∼400 km) current sheet is carried by the cross‐tail serpentine motion of non‐adiabatic ions (Speiser, 1965). The instability of this latter current leads to the local disruption of the near‐earth current sheet.
Lateral variation of Q from singlet modal Q measurements of 0S2
Authors: Tanimoto Toshiro
Published: February 2008

Attenuation parameter Q of five singlets for the spheroidal mode 0S2 (m=−2, −1, 0, 1, 2) are measured from a strain recording for the 1960 Chilean earthquake and three gravimeter recordings for the 1977 Indonesian (Sumbawa) earthquake. From the variation of modal Q as a function of m, three spherical harmonic components of radially averaged Q, angular degree and order (0,0), (2,0) and (4,0), can be determined. The solution indicates lower Q values in the polar regions than in the equatorial regions of the lower mantle, although error bars for (2,0) and (4,0) are large. Assuming a thermally activated process with the activation energy of about 100 kcal/mol, this variation of Q is consistent with a few tens of degrees of lateral temperature variations. With better 0S2 data, large scale temperature variation in the lower mantle can be constrained in principle.
High frequency (1–100 HZ) noise and signal recorded at different depths in a mine, northwest Adirondacks, NY
Authors: Barstow Noël , Carter Jerry A. , Pomeroy Paul W. , Sutton George H. , Chael Eric P. , Leahy Patrick J.
Published: February 2008

Seismograms of noise recorded simultaneously at the surface and at two subsurface stations (335m and 945m below surface level) show that high frequency (1–100 Hz) background noise is reduced at the subsurface stations. Seismometers at all three stations are well coupled to hard crystalline bedrock. Most of the noise reduction occurs between the surface and 335m depth. Between 1 and 3 Hz, seismic noise correlates well with wind speed at all levels. Above 3 Hz, wind speed up to 8 m/sec does not influence high frequency noise levels at 335m or 945m depths. At the surface, however, high frequency noise is associated with wind speeds in excess of 2 m/s. A site resonance is characteristic of the surface spectra, but is not characteristic of the subsurface sites. Spectral signal‐to‐noise (S/N) ratios, measured for S‐waves from a regional earthquake (Δ = 530 km, mb = 4.1), are roughly equal from 1–10 Hz at all depths. Above 10 Hz, however, S/N is greater at the subsurface stations with S/N greater than 1 up to 30 Hz for the surface station, ≈ 50 Hz for the 335m station, and ≈ 70 Hz for the 945m station. Results indicate the advantage of employing high frequency sensors sufficiently below the surface to reduce the level of noise and to improve the S/N ratio in the high frequency range. Such an advantage could be critically important for nuclear test detection and discrimination.
High‐temperature techniques for measuring microcoercivity, crystallite size, and domain state
Authors: Dunlop David J. , Argyle Kenneth S. , Bailey Monika E.
Published: February 2008

We describe three useful techniques for investigating magnetic microstructure and granulometry, high‐temperature alternating‐field (AF) demagnetization, thermal fluctuation analysis (TFA), and determination of the demagnetizing factor N, and give examples of their use. For synthetic magnetite samples, thennoremanent magnetization and anhysteretic rémanent magnetization are shown to differ in their AF demagnetization spectra at all temperatures up to the blocking range. Moreover, various coercivity fractions of either spectrum evolve differently with temperature than does the bulk coercive force. TFA of high‐temperature coercive force data for dispersed magnetite crystals with mean sizes of 215, 390 and 540 run indicate that ≈200 nm regions are thermally activated in each case. These regions may be responsible for pseudo‐single‐domain behaviour. A crude estimate of N for multidomain grains at any temperature is the ratio between bulk coercive force and saturation remanence. The 215–540 nm magnetites appear to contain two or three domains between −100°C and 400°C; new domains may nucleate at higher temperatures.
An algorithm for determining grainsize spectra from plane of cut information
Authors: Robertson D. J.
Published: February 2008

An algorithm is developed for obtaining grainsize distribution by volume from observations of areas of particles exposed in a plane of cut. The approach follows existing methods except that error estimates are included and a logarithmic scale of grainsize is adopted. One tenth decade class intervals in grainsize are suggested, arid there is no limit on the number of orders of magnitude which can be accommodated. The scheme was devised to permit the inventory of magnetic minerals in rocks to be studied, but it may be useful in other branches of petrology.
Radium distribution and indoor radon in the Pacific Northwest
Authors: Duval Joseph S. , Otton James K.
Published: February 2008

Aerial gamma‐ray data were compiled to produce a map showing the distribution of radium (226Ra) in near‐surface materials in the Pacific Northwest (Washington, Oregon, and Idaho, and parts of Montana, Wyoming, California, Nevada, and Utah). A comparison of measurements of indoor concentration levels of radon (222Rn) in homes with the apparent surface concentration of radium shows that aerial gamma‐ray data provide a first order estimate of the relative amounts of indoor radon for township‐sized areas where soils have low to moderate permeability. Townships with average indoor radon levels above the general trend of the data are almost all characterized by soils that have higher intrinsic permeabilities.
Indirect evidences for a gas/dust torus along the Phobos orbit
Authors: Dubinin E. M. , Lundin R. , Pissarenko N. F. , Barabash S. V. , Zakharov A. V. , Koskinen H. , Schwingenshuh K. , Yeroshenko Ye. G.
Published: February 2008

Observations from the PHOBOS‐2 space‐craft of plasma and magnetic field effects in the solar wind near Mars suggest that a neutral gas (dust?)torus/ring resides along the orbit of the Martian satellite Phobos. Magnetic ‘cavities’(strong decreases of the magnetic field strength) coincident with strong plasma density increases (up to a factor of ten) are observed during the first elliptic transition orbits when the spacecraft approached the Phobos orbits. The characteristic transverse dimension of the structures along the spacecraft orbit is in the range 100–1000 km, ‘Torus effects’ also have characteristics similar to the formation of a bow shock with increases of plasma density and ion temperature, and a characteristic deflection of the ion flow. This suggests a rather strong interaction between the solar wind plasma and plasma near Phobos orbit. The interaction appears quite similar to that of the solar wind with a comet. The oiitgassing of matter from Phobos (and Deimos) is also suggested by plasma observations in the wake/tail of the Martian satellites. Altogether, our observations imply that a neutral gas cloud—possibly also associated with a faint dust ring—exists along the Phobos orbit.
Martian bow shock: Phobos observations
Authors: Schwingenschuh K. , Riedler W. , Lichtenegger H. , Yeroshenko Ye. , Sauer K. , Luhmann J. G. , Ong M. , Russell C. T.
Published: February 2008

Data obtained with the MAGMA magnetometer on the subsolar passes of the Phobos spacecraft during its 3 elliptic orbits reveals a turbulent bow shock with a strong foot consistent with the reflection of solar wind protons. The bow shock lies at a subsolar distance of 1.47 ± .03 RM. The circular orbit phase of the mission reveals a bow shock with a highly varying location. The median terminator crossing lies at 2.72 Mars radii. The location of the bow shock in the terminator plane is sensitive to neither the EUV flux nor to planetary longitude.
Effects of ion temperature anisotropy on the interhemispheric plasma transport during plasmaspheric refilling
Authors: Singh Nagendra , Torr D. G.
Published: February 2008

Effects of temperature anisotropies on the early stage refilling of the outer plasmasphere are studied by solving an appropriate set of hydrodynamic equations. The anisotropies result from the supersonic outflows from the conjugate ionospheres and from the perpendicular ion heating in the equatorial region. The equatorial ion heating affected by wave‐particle interaction is included phenomenologically. Even for the equatorial heating associated with moderate wave levels, the mirror force on the flows severely limits the interhemispheric plasma exchange. The temporal evolution of the flow developing in an empty flux tube is characterized by: (1) supersonic plasma outflows from the conjugate ionospheres, (2) reflections of the flows by the mirror force as they begin to penetrate into the opposite hemispheres, (3) formation of shocks in the reflection region and (4) propagations of the shacks to the ionospheres of the origins of the flows. In the quasi‐steady state when flow completely subsides, the density distribution in the flux tube shows distinctive large‐scale features, determined by the balance between electric, pressure and anisotropy forces. The latter force becomes significant in a broad equatorial region where Tt > > Tp and also at relatively high geomagnetic latitudes where Tt < < Tp; Tt and Tp are the perpendicular and parallel ion temperatures, respectively. The force balance at high latitudes keeps the flux tube far from completely filled with minimum density < 10−1n0, where n0 is the ionospheric density. The equatorial ion population with Tt > > Tp is found to be similar to the trapped ions observed from satellites.
Historic trend of the levels of atmospheric H2O2 during 1960's – 1980's in Los Angeles
Authors: Sakugawa Hiroshi , Tsai Wangteng , Kaplan Isaac R. , Cohen Yoram
Published: February 2008

The historic trend of the levels of gaseous H2O2 during 1960's–1980's in Los Angeles was assessed from field date and numerical simulations. The results indicate that during 1960's–1970's concentrations of H2O2, as well as O3, were likely to have been higher than those during 1980's, For the period 1969–1987, predicted summer peak concentrations of H2O2 and O3 in the ground level atmosphere were in a range of 6–10 ppb and 200–350ppb, respectively. Also H2O2 and 03 concentrations decreased by about 35% and 42% respectively from the levels of 1975 to 1987. Model simulations indicated that the reduction of NMHC and CO emissions from industrial and automotive sources have resulted in the decrease in H2O2 levels during the late 1970's–1980's, whereas the reduction of NMHC, CO and NOx emissions have resulted in lower O3 levels. The role of H2O2 as an oxidant for SO2 and as a possible toxin on trees in Los Angeles and surrounding mountains during the past decades are discussed. From the historic data of atmospheric levels of sulfate in Los Angeles, we suggest that the decrease in the levels of H2O2 and O3 may have contributed to the decrease in sulfite levels during the 1980's.
Horizontal motions due to post‐glacial rebound
Authors: James Thomas S. , Morgan W. Jason
Published: February 2008

North American horizontal post‐glacial rebound velocities are computed for three five‐layered, incompressible, spherical Maxwell earth models, using a simple glacial loading cycle centered on Hudson Bay. The reference earth model has a 120‐km thick elastic lithosphere and upper‐ and lower‐mantle viscosities of 1021 Pa·s and 2 × 1022 Pa·s, respectively. The second model has a lower viscosity upper‐mantle (5 × 1020 Pa·s) and a higher viscosity lower‐mantle (1023 Pa·s), and the third has a 250‐km thick lithosphere. The reference model and the low‐viscosity upper‐mantle model calculations are in good agreement with uplift and gravity data, although they may somewhat overestimate the present‐day central uplift rate. The thick lithosphere model fares less well because it fails to exhibit the well‐pronounced peripheral bulge sinking that is required by eastern North America tide gauge data. The reference model generally has the largest horizontal rebound velocities, reaching a maximum of 4 mm/yr towards Hudson Bay at 2400 km from the load center. The effect of a thick lithosphere or of a low‐viscosity upper‐mantle is to reduce present‐day horizontal velocities, especially in the formerly glaciated region. The sensitivity of horizontal motions to lithospheric thickness and upper‐mantle viscosity may assist in discriminating between different models of the earth's rheology once sufficient high‐quality geodetic data exist.
Fractal boundaries in magnetotail particle dynamics
Authors: Chen J. , Rexford J. L. , Lee Y. C.
Published: February 2008

It has been recently established that particle dynamics in the magnetotail geometry can be described as a nonintegrable Hamiltonian system with well‐defined entry and exit regions through which stochastic orbits can enter and exit the system after repeatedly crossing the equatorial plane. It is shown that the phase space regions occupied by orbits of different numbers of equatorial crossings or different exit modes are separated by fractal boundaries. The fractal boundaries in an entry region for stochastic orbits are examined and the capacity dimension is determined.
The structure of the Birkeland current system in the post‐midnight plasma sheet
Authors: Nagai Tsugunobu , Takahashi K. , Potemra T. A. , McEntire R. W. , Lopez R. E. , Klumpar D. M.
Published: February 2008

Simultaneous magnetic field and particle measurements by AMPTE/CCE with magnetic field measurements by GOES 5 and GOES 6 clarify the structure of the field‐aligned Birkeland current system in the post‐midnight region of the near‐Earth magnetotail. The current system, consisting of current sheets flowing in opposite directions, exists near the boundary region of the plasma sheet; its magnetic effects are confined mainly to the current region because of its structure. During the expansion phase of substorms, a single‐sheet current system is formed in the boundary region of the plasma sheet and net current is probably present in one meridian plane. This type of current system produces the substorm‐related transient variations in the azimuthal (D) component normally observed at synchronous orbit.
Geomagnetic activity for northward interplanetary magnetic fields: AM index response
Authors: Scurry L. , Russell C. T.
Published: February 2008

The Am index is used to study the response of the magnetosphere to northward IMF. It is shown that most of the observed increase in activity can be explained by a correlation of the solar wind dynamic pressure with the IMF field strength such that the Am index varies only slightly with northward IMF strength when the solar wind dynamic pressure is held constant. There remains a smaller response of Am to solar wind velocity, which is usually attributed to a viscous interaction of the solar wind with the magnetosphere such as through the Kelvin‐Helmholtz instability. The diurnal variation of Am during northward fields is also examined. A model invoking the Kelvin‐Helmholtz instability on the flanks of the magnetopause have been used to predict the annual behavior of this diurnal variation. The predicted annual behavior is not found for northward IMF. The difference in diurnal variation from summer months to winter months, suggested to be caused solely by the Kelvin‐Helmholtz instability, appears only for southward fields. Thus, while the Kelvin‐Helmholtz instability may play some role in energy transfer into the magnetosphere and the resultant geomagnetic activity, this role is much less than that of dynamic pressure fluctuations and we find no evidence that it by itself plays any role in the annual variation of the diurnal variation of geomagnetic activity.
Latitudinal evolution of the Réunion hotspot deduced from paleomagnetic results of Leg 115
Authors: Vandamme Didier , Courtillot Vincent
Published: February 2008

During ODP Leg 115 in the Indian Ocean, four holes penetrated the basement. Paleomagnetic measurements on basement cores yield good quality results, but their interpretation is limited by possible but often undetectable subsequent tectonic tilting, and in one case by insufficient averaging of secular variation. Two Sites (64 and 55–60 Ma) yield apparently reliable results. Results from sediments of another Site (36 Ma) studied by Schneider and Kent also appear to be reliable. The three corresponding paleolatitudes are roughly in agreement with values predicted from the synthetic apparent polar wander paths of the African and Indian plates. Together with results from the Deccan (67 Ma), they indicate smooth and rather slow (8mm/yr) northward drift of the Réunion hotspot since its inception at the Deccan. This motion is consistent with the hotspot models of Morgan and Duncan.
Evidence for errors in the geomagnetic polarity time‐scale at 17–15 Ma: 40Ar/39Ar dating of basalts from the Pacific Northwest, USA.
Authors: Baksi Ajoy K. , Farrar Edward
Published: February 2008

40Ar/39Ar incremental heating studies have been carried out on whole‐rock basalt samples from the Columbia River Basalt (CRB) and the Steens Basalt, to obtain crystallization ages with a standard error <1%. These high precision, accurate, ages are utilized with the known magnetostratigraphy of the CRB, to test the accuracy of the Early to Middle Miocene section of the geomagnetic polarity time‐scales currently in use. We conclude that these time‐scales underestimate the ages of various chrons within this time range by ∼0.9 m.y.
Trapping of aqueous fluids in the deep crust
Authors: Bailey R. C.
Published: February 2008

Free aqueous fluids in the deep (ductile) crust have residence times there which are very short in geological terms. If not consumed by retrograde metamorphic reactions, they empty very rapidly upwards. This can be shown by applying the theory of magma percolation in a ductile host to the problem of aqueous fluid percolation. Below the brittle‐ductile transition thermal activation of ductility is strong enough to facilitate the rapid evolution of porosity and consequently allow rapid fluid transport. In the cooler crust above the brittle‐ductile transition, however, this mechanism vanishes. As a consequence, fluid overpressures resulting from the accumulation of fluid in the transition zone must induce hydraulic fracturing rather than pore inflation. In regions of horizontally compressive regional stress, the commonest situation in stable continental crust, these fractures will be horizontal. Aqueous fluids rising through or liberated from the lower crust will therefore probably accumulate (at least initially) at the brittle‐ductile transition in horizontally extensive reservoirs with high horizontal permeability but low vertical permeability.
Polarizations of reflected shear waves
Authors: Liu Enru , Crampin Stuart , Yardley Gareth
Published: February 2008

Past seismic investigations have relied principally on analysis of first arrival P waves with longitudinal particle displacements rather than the slower shear waves with more complicated transverse motions. Consequently, even quite elementary behavior of shear waves is sometimes poorly understood. It might be supposed, that the direction of polarization of shear waves would remain essentially unchanged on reflection from a plane horizontal isotropic‐to‐isotropic interface. This paper shows that in general this is not the case. In some circumstances, the direction of polarization can rotate by almost 180° as the angle of incidence varies. Since there is growing interest in using shear wave polarizations to examine the internal (anisotropic) structure of the rockmass in both earthquake and exploration seismology, such anomalous behavior of shear wave polarizations is important for understanding the behavior of shear waves and investigating the structure of the crust. The anomalies we display are a necessary result of the behavior of the reflection coefficients, which are well‐known, but the possibility of such wide variations in polarization of the reflected shear wave does not appear to have been recognized previously in the literature.
Winds in the upper mesosphere at mid‐latitude: First results using an imaging Fabry‐Perot Interferometer
Authors: Rees David , Aruliah Anasuya , Fuller‐Rowell Timothy J. , Wickwar Vincent B. , Sica Robert J.
Published: February 2008

The first stage of a new midlatitude facility at the Hardware Ranch Observatory near Bear Lake (41.93°N, 111.42°W, 1970 M elevation), for studies of the aeronomy of the middle and upper atmosphere, was completed during early September 1989. An Imaging Fabry‐Perot interferometer (IFPI) (Rees et al., 1982; Rees et al., 1990), was commissioned with a special Imaging Photon Detector (IPD) (McWhirter et al., 1982), equipped with a Gallium Arsenide (GaAs) photocathode. Wind and temperature structure can be deduced from observations of the Doppler shift and Doppler broadening of airglow and auroral emissions from the mesosphere and thermosphere. The near infra‐red Meinel bands from near 86 km in the upper mesosphere were observed with the IFPI and show 40 ms−1 amplitude wind oscillations, consistent with a semi‐diurnal tidal mode.
Observations of backscatter, particle concentration and frost point in north polar vortex stratospheric clouds
Authors: Rosen James M. , Kjome Norman T. , Oltmans Samuel J.
Published: February 2008

Near‐simultaneous soundings of backscatter, particle size distribution and frost point were obtained in north polar stratospheric clouds (PSCs) near the center of the vortex. The measured particle sizes and concentration in type I PSCs tend to confirm earlier predictions based on remotely sensed properties.
Cloud condensation nuclei over the Southern Ocean
Authors: Gras John L.
Published: February 2008

The basis of a cloud condensation nucleus (CCN) climatology program has been in place at Cape Grim (Tasmania) since 1982. This has shown both marked seasonal variation and evidence of interannual variation in CCN concentration. CCN concentrations have been found to be substantially understandable in terms of the condensation or Aitken nucleus (CN) concentration and size. Whether CCN concentrations are systematically changing in response to climate change and/or increasing anthropogenic sulfur emission is an unresolved question. Although present CCN concentrations are higher than those reported for clean oceanic regions two decades earlier, the data do not allow confident conclusions about the cause.
Influence of equatorial QBO and SST on polar total ozone, and the 1990 Antarctic Ozone Hole
Authors: Angell J. K.
Published: February 2008

Based on data through 1989, comparisons are made between the variation of total ozone at Resolute, Canada (75°N) and South Pole, and the variation of low‐stratospheric temperature at Singapore (reflecting the equatorial QBO) and SST in eastern equatorial Pacific (reflecting the ENSO phenomenon). Total‐ozone variations at Resolute have been more closely related to the QBO, whereas the total‐ozone variations at South Pole appear to have been almost equally related to QBO and SST. When the average of 50 mb and 30 mb June‐July‐August (JJA) values of Singapore temperature (
) increased from one year to the next, the decrease in South Pole springtime total ozone for the same years averaged 21 ± 14% greater than when
decreased. When the JJA values of equatorial SST increased from one year to the next, the decrease in South Pole springtime total ozone for the same years averaged 18 ± 12% greater than when SST decreased. In the 6 cases when JJA values of both Singapore
and equatorial SST increased from one year to the next, the spring values of South Pole total ozone have decreased, whereas in the 6 cases when both
and SST decreased from one year to the next, South Pole total ozone has increased. Both Singapore
and equatorial SST will probably be warmer in JJA of 1990 than they were in JJA of 1989 suggesting, based on these previous relations, an even deeper Antarctic ozone hole in 1990 than in 1989 and ending the biennial variation in depth of the hole of the last 6 years.
The position of the magnetotail neutral sheet in the near‐Earth region
Authors: Lopez Ramon E.
Published: February 2008

The position of the near‐earth neutral sheet throughout the nightside region between R = 5 RE and R = 8.8 RE is examined statistically using magnetic field data from AMPTE/CCE. As has been demonstrated previously, the latitudinal position of the neutral sheet is primarily controlled by the dipole tilt angle. The position also depends on local time, radial distance, and magnetic activity. These dependencies may be represented by the empirical formula MLAT = − (0.14 Kp + 0.69) [cos(Φ)]1/3 (0.065 R0–8 − 0.16) DTA, where MLAT is the position in degrees of the neutral sheet relative to the magnetic equator, Kp is the 3‐hourly magnetic activity index, Φ is the magnetic local time in degrees (midnight = 0°), R is the radius in RE, and DTA is the dipole tilt angle in degrees.