bluuebunny/crossref_metadata_2025 huggingface dataset:
On the heliographic latitude dependence of the interplanetary magnetic field as deduced from the 22‐year cycle of geomagnetic activity
Authors: Russell C. T.
Published: February 2008

The geomagnetic activity index, Ci, exhibits a double sunspot cycle in which 11‐year periods alternately have more, then less, than average activity. The amplitude of the cycle‐to‐cycle variation has varied markedly since 1885, being large from 1885 to 1907, small from 1908 to 1948 and large again from 1949 to 1970. If we assume that the 22‐year variation is caused by reversals every sunspot cycle of the heliographic latitude dependence of the dominant polarity of the interplanetary magnetic field, the behavior of the Ci index implies that the amplitude of the heliographic latitude dependence varies with time. If, as has been proposed, the heliographic latitude dependence is associated with the magnetic field at the solar poles, then the Ci index variation also implies that the polar magnetic field strength has undergone long‐term changes.
Evidence for late formation and young metamorphism in the Achondrite Nakhla
Authors: Papanastassiou D. A. , Wasserburg G. J.
Published: February 2008

We have determined an age T=1.37 AE for Nakhla and an initial 87Sr/86Sr, I = 0.7023. A rather thorough Sr equilibration took place at this time between all the phases of this meteorite, but there is clear evidence of somewhat incomplete isotopic equilibrium during the 1.37 AE event, which is not consistent with the derivation of Nakhla from a magma at this time. Nakhla has a young model age of 3.6‐2.9 AE which requires that gross differentiation processes for its parent body occur between 3.6 and 1.37 AE, significantly later than 4.6 AE. The most reasonable model is that Nakhla formed as an igneous rock at ∼3 AE and was metamorphosed at 1.37 AE. Several similarities exist between the Nakhla parent planet and the Earth and indicate the existence of other objects with close terrestrial chemical affinities.
Current estimates of mean Earth ellipsoid parameters
Authors: Rapp Richard H.
Published: February 2008

Independent estimates of a, J2, kME (of the solid earth), Ro (scale factor for lengths), γe (equatorial gravity) and a fixed ω are used in a weighted least squares adjustment to determine adjusted values for the variable parameters assuming a rotational equipotential ellipsoid as the figure of reference. The adjusted values are: kME = (3.9860034±0.0000023)×1014 m³/sec²; γe = 978031.69±0.77 mgals; f = 1/(298.25636±0.00147); Ro = 6363674.98±2.50 m, a = 6378139.0±2.51m and Wo (the geoid potential) = 6263681.62kgal m.
Diffusionless dilatancy model for earthquake precursors
Authors: Stuart William D.
Published: February 2008

A dilatancy model without extensive pore fluid diffusion is proposed as an explanation for time‐dependent geophysical anomalies occurring prior to earthquakes. As with the fluid flow models, the creation of thin dry or undersaturated cracks due to progressive distortion near the focal region is assumed. Rather than invoking fluid migration from the surrounding crust to fill cracks, the cracks are thought to close again before the earthquake because of decreasing stress levels imposed by strongly nonlinear constitutive properties of fault zone material. The proposed model and the fluid flow model predict qualitatively similar Vp/Vs, and resistivity histories. Whereas the fluid flow model predicts maximum epicentral uplift due to dilatancy at the time of the earthquake, the diffusionless model predicts uplift followed by subsidence prior to the earthquake, as well as premonitory creep in the focal region.
Crustal and upper mantle stratigraphy beneath eastern Kansas
Authors: Brookins D. G. , Meyer H. O. A.
Published: February 2008

The kimberlites of Riley County, Kansas contain xenoliths of upper mantle and crustal rocks. The kimberlite probably originated below the Low Velocity Zone (LVZ). Deep seated xenoliths include ilmenite‐pyroxene symplectites, lherzolite, and eclogite. Other xenoliths from below the Moho include pyroxenites, plagioclase‐bearing eclogites, and several types of granulites. Above (or near) the Moho (35 kilometers depth) occur granulites overlain by metanorites which in turn are overlain by noritic‐gabbroic rocks and diorites. Metamorphic amphibolite and schistose xenoliths are rare, as too are granitic rocks. Presumably the granites occur below the Rice Formation (Arkosic Rocks) and Clay Formation (Basaltic Rocks) which are in fault contact with each other and extend into the midcontinental region from the Lake Superior Province. Above the Precambrian basement, there occurs approximately 1.7 kilometers of Paleozoic shales and limestones; xenoliths of these rocks are common in the kimberlite diatremes.
The distribution of Sr and REE between diopside and silicate liquid
Authors: Grutzeck M. , Kridelbaugh S. , Weill D.
Published: February 2008

Distribution coefficients (weight concentration in the solid divided by concentration in the liquid) have been determined experimentally in diopside‐liquid pairs. Experiments were carried out in air at 1265 °C in the system NaAlSi3O8‐CaAl2Si2O8‐CaMgSi2O6 at the two bulk compositions: 5‐30‐65 and 32‐11‐57 (weight percentage of components in the order given above). Small differences are observed in the distribution coefficients between the two compositions. Mean values of the coefficients in the first system are: Sr=.078, La=.069, Ce=.098, Nd=.21, Sm=.26, Eu=.31, Gd=.30, Dy=.33, Er=.30 and Lu=.28. At low oxygen fugacities of 10−9.5 and 10−12.5 atmospheres the distribution of Eu between diopside and liquid develops a “negative Eu‐anomaly” with coefficients of .23 and .12 respectively.
Identification of fault planes associated with deep earthquakes
Authors: Billington Selena , Isacks Bryan L.
Published: February 2008

Application of the method of Joint Hypocenter Determination (JHD) to carefully determined arrival time data from a small network of sensitive and well‐distributed local and teleseismic stations provides very precise locations of deep earthquakes. The precision of locations attained by this method—the relative locations are good to about 5 km—is limited mainly by the accuracy and precision of the measurements of arrival times. Application of the technique to a small and very active part of the deep earthquake zone of the Tonga island arc (depths near 600 km) reveals probable fault planes associated with the occurrence of deep earthquakes. The spatial distribution of precisely relocated hypocenters is closely related to the orientation of the focal mechanism solutions of two deep earthquakes. Hypocenters cluster in a plane parallel to one of the nodal planes for each of the two solutions examined. The planar features are yearly vertical and have linear dimensions of about 40 km. In one case the shocks defining the fault plane also tended to cluster in time near the occurrence of the largest event. These and other data suggest the existence of several distinct fault planes in the area studied. Our study is being extended to examine the structure of the entire Tonga deep seismic zone.
On the radial variation of the interplanetary magnetic field: Pioneer 6
Authors: Villante U. , Mariani F.
Published: February 2008

Analysis of simultaneous plasma and magnetic field observations by Pioneer 6 suggests, at heliocentric distances of 0.8 to 1.0 AU, significant deviations from Parker's theory: in particular, a radial variation as r−2 is estimated for the azimuthal magnetic field component.
Tornado characteristics revealed by Doppler radar
Authors: Burgess Donald W. , Lemon Leslie R. , Brown Rodger A.
Published: February 2008

A Doppler velocity signature of large shear coincident with tornado location has been discovered in an Oklahoma thunderstorm. The gate‐to‐gate tangential shear (GGS) signature is used to draw conclusions concerning vertical depth of the tornado vortex and its apparent descent from storm mid‐levels to the surface.
Pressure effect on water content of amphiboles
Authors: Kuroda Yoshimasu , Hariya Yu , Suzuoki Tetsuro , Matsuo Sadao
Published: February 2008

The water content of synthetic amphibole (richterite50 + tremolite50 solid solution) markedly increases with increase in the vapor pressure in the range from 5 to 20 kb at fixed temperatures. Temperature change from 750°C to 900°C at fixed pressures does not affect the water content of synthetic amphiboles. The water content of common hornblende from ultramafic‐mafic rocks is found to be always higher than that from granitic rocks. This difference indicates a difference in the confining pressure of formation of two rock types.
High resolution daytime photoelectron energy spectra from AE‐E
Authors: Doering J. P. , Peterson W. K. , Bostrom C. O. , Potemra T. A.
Published: February 2008

The daytime photoelectron energy spectrum has been measured at altitudes above 154 km by the photoelectron spectrometer experiment on the Atmosphere Explorer‐E satellite. Much higher energy resolution spectra than previous AE‐C results have been obtained. Below 200 km, well resolved peaks are observed in the spectrum corresponding to production of O+ and N2+ in various electronic states from photoionization of N2 and O by solar He II (304A) radiation. Vibration‐rotation excitation of N2 by inelastic electron scattering is observed at 2.5 eV. The features due to nitrogen disappear from the spectrum at altitudes above 200 km.
Interpretation of heat flow measurements in the Vema Fracture Zone
Authors: Langseth Marcus G. , Hobart Michael A.
Published: February 2008

23 measurements in the floor of the Vema Fracture Zone show heat flow to be above normal and remarkably uniform between the active spreading centers (HF = 3.5 HFU). A simple thermal model of a transform fracture zone shows that heat flow over the fault plane should equal the means of the heat flows over the two abutting lithospheric plates. This model predicts a rather uniform heat flow between the two spreading centers.
Nd isotopic variations and petrogenetic models
Authors: DePaolo D. J. , Wasserburg G. J.
Published: February 2008

The decay of 147Sm to 143Nd allows 143Nd/144Nd to be used to trace Sm/Nd fractionation in long time‐scale geologic processes. 143Nd/144Nd has been measured in terrestrial rock samples of different ages to establish the characteristics of Nd isotopic evolution in the crust and mantle. The evolution of 143Nd/144Nd in the mantle indicates Sm/Nd essentially equal to that of chondrites, and implies a chondritic REE distribution for the earth. Variations in 143Nd/144Nd do exist in the mantle, however, indicating Sm/Nd heterogeneity and the existence of distinct mantle reservoirs with characteristic 143Nd/144Nd. 143Nd/144Nd in average crustal rocks today is much lower than found in recent mantle samples and reflects their age and low Sm/Nd. Oceanic tholeiites and alkali basalt are derived from sources with Sm/Nd which has been 5‐10% greater than chondritic over the age of the earth. Alkali basalt can not be derived from mantle reservoirs which have been light REE‐enriched for long times.
Height variation of wind speed and wind distributions statistics
Authors: Justus C. G. , Mikhail Amir
Published: February 2008

For use in various wind engineering applications (e.g. wind energy conversion, wind loads on structures, air pollution transport) it is desirable to have a consistent relationship by which to project height variations of both "instantaneous" (e.g. few minute average) winds and parameters of the wind speed probability distribution. The power law V2/V1 = (Z2/Z1)n is often used for height projection of wind profiles, with the exponent n sometimes taken as depending on surface conditions or on atmospheric stability. The power law profile for wind speed is shown here to be consistent with observed height variation of Weibull wind speed probability distribution functions which have been found to fit observed wind speed distributions (at least above relevant threshold wind speeds). For consistency between the wind speed profiles and the height variation of the Weibull wind speed probability distributions, it is necessary only that the exponent n vary as n = a + b ℓn V1, where a and b are constants whose values depend on the reference height at which wind speed V1 is measured. For a reference height of 10 m, it is found that a = 0.37 and b = −0.0881 (with V1 in m/s) adequately describes both the observed height variation of wind speed and wind speed probability distributions.
Combustion as a source of nitrous oxide in the atmosphere
Authors: Pierotti David , Rasmussen R. A.
Published: February 2008

Recent measurements of the exhaust gases in the stacks of power plants burning coal and natural gas have shown high levels of nitrous oxide. Calculations based upon the known combustion parameters of the power plants and extrapolated to the current world production of coal and natural gas indicate that combustion may be a significant source of nitrous oxide in the atmosphere. In view of the predicted increases in the combustion of fossil fuels, particularly coal, it is likely that the importance of combustion as a source of atmospheric nitrous oxide will increase. As a result of the current uncertainty regarding the size of the various sources and sinks of nitrous oxide in the atmosphere, it would appear that the question of the importance of combustion to the atmospheric nitrous oxide budget deserves further scrutiny.
Trace metal concentration as a function of particle size in marine aerosols from Bermuda
Authors: Duce R. A. , Ray B. J. , Hoffman G. L. , Walsh P. R.
Published: February 2008

Three samples of marine aerosols were collected from a 20 m high tower on the coast of Bermuda using a high volume cascade impactor. The elements Na, Al, Fe, Mn, Sc, Th, and Co were found primarily on particles with aerodynamic equivalent radii of approximately 1 µm or greater and their source is likely either the sea (Na) or crustal weathering. However, the elements Cu, Zn, As, Cd, Pb, Sb, Se, and Hg are present in concentrations too high to be explained by a bulk seawater or normal crustal weathering source. The major mass of these elements is present on particles with equivalent radii less than 1 µm;, suggesting that a volatile phase is critical at some stage of the atmospheric lifetime of these anomalously enriched elements in mid‐ocean marine aerosols.
The solubilization of anthropogenic atmospheric vanadium in sea water
Authors: Walsh Paul R. , Duce Robert A.
Published: February 2008

A major fraction of the anthropogenically derived enriched V on atmospheric particles is rapidly solubilized in sea water. The generally longer residence times of soluble species relative to particles indicates that pollution V in the ocean will be long‐term although this input source will not significantly increase the oceanic V reservoir.
A rocket measurement of the O2(b1Σg+ − X3Σg−) atmospheric band nightglow altitude distribution
Authors: Deans A. J. , Shepherd G. G. , Evans W. F. J.
Published: February 2008

A rocket measurement of the
atmospheric band altitude distribution in the nightglow has been made under high latitude winter conditions. An integrated intensity of 1.4kR was observed with a peak volume emission rate of 750 photons cm‐3 sec‐1 at 91 km. An atomic oxygen altitude distribution with a number density of 1.7 × 1011 cm‐3 at 100 km is derived.
Densities of fertile and sterile garnet peridotites
Authors: Boyd F. R. , McCallister R. H.
Published: February 2008

Densities of a fertile peridotite (PHN 1611) and a depleted sterile peridotite (PHN 1569) have been calculated to be 3.39 and 3.30, respectively. These densities were calculated from the cell dimensions of the component minerals, the mineral analyses, and the bulk rock analyses. Studies of kimberlite nodules suggest that lighter, sterile peridotites overlie heavier, more fertile peridotites uniformly in the upper mantle beneath southern Africa. A temperature difference of 500°C reduces the density of fertile peridotite PHN 1569 to approximately 3.33, which is insufficient to cause it to float in sterile peridotite. However, if fertile peridotite PHN 1569 undergoes 25% partial melting and the garnet is dissolved, its zero pressure density would be reduced to approximately 3.2, which is less than that of depleted, sterile mantle.
Mariner 10: Mercury atmosphere
Authors: Broadfoot A. L. , Shemansky D. E. , Kumar S.
Published: February 2008

Reduction of data from the three Mariner 10 encounters to this date have allowed identification of helium and hydrogen as atmospheric constituents. Subsolar point densities are estimated at 4500 cm−3 for He and 8 cm−3 for the thermal component of H. A non‐thermal component in H with a scale height of ∼ 70 km has been observed near the limb off the subsolar point, providing a total apparent number density of 90 cm−3. Upper limits on other atmospheric constituents have been reduced an order of magnitude. A very tentative identification of O has been obtained but the uncertainty is large and we require further data reduction for confirmation.
Atmospheric circulation: Exploration over Antarctica and seasonal variations
Authors: Singh Sehra Parmjit
Published: February 2008

Seasonal wind variations over Antarctica in an altitude region from surface up to about 80 km are studied using data from 52 successful M‐100 meteorological rocket soundings at Molodezhnaya, Antarctica where the author worked during 1971‐73. It is found that the South Polar summer was characterised by light easterly winds increasing in strength with altitude and the winter exhibited strong westerly winds halving jet speeds of about 90 m/s increasing in strength as the season progressed, while the autumn and the spring were the wind reversal periods. The Antarctic winter regime was the most active period with a wind persistence of about 95% marked by strong westerly flow. Departures of the actual zonal winds from the Groves Model were found to be quite significant showing hemispheric asymmerties in the Northern and the Southern Hemispheres. The physical properties of the immense southern oceans play an important role in these differences.
Inferences about magma sources and mantle structure from variations of 143Nd/144Nd
Authors: DePaolo D. J. , Wasserburg G. J.
Published: February 2008

Continental flood basalts and mid‐ocean ridge (MOR) tholeiitic basalts have distinctly different 143Nd/144Nd which may permit a priori distinction between "continental" and "oceanic" igneous rocks. Initial 143Nd/144Nd of continental igneous rocks through time fall on a Sm/Nd evolution curve with chondritic REE abundance ratio. These observations indicate that many continental igneous rocks are derived from a reservoir with chondritic REE pattern which may represent primary material remaining since the formation of the earth. Oceanic igneous rocks are derived from a different ancient reservoir which has Sm/Nd higher than chondritic. Initial 143Nd/144Nd and 87Sr/86Sr in young basalts from both oceans and continents show a strong correlation suggesting that Sm‐Nd and Rb‐Sr fractionation events in the mantle may be correlative and caused by the same process. From this correlation Rb/Sr for the earth is inferred to be 0.029.
Daytime satellite radio scintillation and sporadic E near the magnetic equator
Authors: Rastogi R. G. , Deshpande M. R. , Murthy B. S. , Davies K.
Published: February 2008

The radio beacon signals on 40 MHz, and 140 MHz and 360 MHz from ATS‐6 satellite at 34°E longitude, received at Ootacamund, India (11.43°N, 76.70°E, dip 4°N) are found to have intense scintillations during daytime on some occasions. These daytime scintillation events are not associated with the q type of sporadic E layer as seen at Kodaikanal (10.23°N, 77.49°E, 3.5N) but are due to the intense ionisation patches in the E region indicated by occurrence on the ionograms of the non q type i.e. either high or flat type of sporadic E layer which either shows multiple reflections or blankets the higher reflections.
The sources of island arcs as indicated by Nd and Sr isotopic studies
Authors: DePaolo D. J. , Wasserburg G. J.
Published: February 2008

Island arc lavas from New Britain and the Marianas have 143Nd/144Nd similar to other oceanic basalts and distinctly different from continental flood basalts and thus appear to be derived from a high Sm/Nd, light‐REE‐depleted reservoir. Consideration of both Nd and Sr isotopes suggests seawater involvement in the generation of some island arc lavas and thus indicates that they may be derived from altered subducted oceanic crust. Other island arc lavas show no evidence of seawater involvement and may be derived from mantle reservoirs with affinities to the sources of ocean island basalts. Andesite and rhyolite from an Andean volcano reflect assimilation of old continental crust. Nd and Sr in basaltic and ultrapotassic continental rocks indicate that some mafic magmas in continental regions may be derived from old low‐Sm/Nd reservoirs or are heavily contaminated with old continental crustal material. Fish debris from the ocean floor provides an estimate of 143Nd/144Nd in seawater and indicates that light‐REE in the marine environment are derived mainly from continents. Basalts erupted above sea level in oceanic and continental areas are isotopically distinct from those erupted on the ocean floor, suggesting a relationship between parental reservoirs and hydrostatic head.
A double Benioff Zone beneath the central Aleutians: An unbending of the lithosphere
Authors: Engdahl E. R. , Scholz C. H.
Published: February 2008

Seismicity located using the Adak seismograph network shows the Benioff zone below a depth of 100 km consists of two thin zones of earthquakes about 25 km apart that merge at a depth of 175 km. Focal mechanisms in the upper zone are consistently down‐dip compression, while those of the lower zone are down‐dip tension. An elastic‐plastic model of the lithosphere predicts that these two zones reflect the stresses in the elastic core of the lithosphere due to unbending.
Atmospheric concentrations of carbonyl sulfide in the southwestern and eastern United States
Authors: Maroulis P. J. , Torres A. L. , Bandy Alan R.
Published: February 2008

Atmospheric concentrations of OCS were measured in the Southwestern and Eastern United States. The average concentrations were 435 ± 54, 454 ± 31 and 511 ± 36 parts‐per‐trillion by volume at Philadelphia, Pa., Wallops Island, Va. and Lawton, Okla., respectively. The data suggest that the lifetime of OCS is much longer than common atmospheric sulfur gases such as H2S and SO2, and that the OCS sources are diffuse and are not concentrated in urban areas. The transport of OCS to the stratosphere from the troposphere may be an important source of stratospheric sulfur.
Consequences of a past encounter of the Earth with an interstellar cloud
Authors: McKay Christopher P. , Thomas Gary E.
Published: February 2008

In its motion through the galaxy the sun may have suffered a number of encounters with dense interstellar clouds for which the number density of molecular hydrogen H2 is > 10³ cm−3. Several authors have shown that this is sufficient density to stop the solar wind inside the earth's orbit. The earth's atmosphere would be subjected to an interstellar H2 flux of > 7×109 cm−2 s−1 for periods of ∼ 105 years. We have examined by means of simple scaling arguments several consequences for the earth's atmosphere: (1) the ionospheric F‐region would largely disappear; (2) the water vapor content of the middle atmosphere would be greatly enhanced, reducing the mesospheric ozone concentrations and thereby lowering the average temperature and altitude of the mesopause; (3) as a result of (2), widespread mesospheric ice clouds would occur, increasing the planetary albedo; (4) the resultant radiative cooling at the surface may have been sufficient to "trigger" an ice age.
The auroral 2150 Å feature: A contribution from lines of singly ionized atomic nitrogen
Authors: Dick K. A.
Published: February 2008

The observed auroral spectral feature at ∼ 2150 Å may consist partially of spin forbidden transitions in singly ionized atomic nitrogen, N II. These transitions are analogous to the 1356 Å feature of O I in that they represent transitions from the lowest lying quintet term to the ground state ³P. Prior consideration of these transitions may have been hampered both by the uncertainty of a precise wavelength value for the observed auroral spectral feature (due to its evidently complex nature) and by the relatively recent determination of the wavelengths of intercombination lines joining the quintet levels of N II to the more abundant triplet and singlet levels.
Relative timing of rifting and volcanism on Earth and its tectonic implications
Authors: Sengör A. M. Celal , Burke Kevin
Published: February 2008

Rifts occur in diverse tectonic environments that result from the continuous two‐dimensional evolution of the multi‐plate mosaic of the Earth and also from the interaction between the mantle processes and the overlying lithosphere. Most rifts have associated volcanics that are mainly basaltic. In continental rifts these basalts are predominantly alkaline and the relative timing of rifting and volcanism is variable; however, despite this variation there seem to be two basic types of rifting‐volcanism relative timing: in one, volcanism and usually local doming predates major rift formation whereas, in the other, rifts form first and volcanism (? and doming) follow thereafter. These two basic types of rifting‐volcanism relative timing may be related to two basic modes of rifting. In the first the mantle plays an active role, convection ‘plumes’ dome up and crack the lithosphere, whereas, in the second, the horizontal movements of plates give rise to extension of the lithosphere and induce rifting. In this latter case, the mantle is passive. Numerous local conditions complicate this simple pattern and result in extremely complicated rifting‐volcanism relationships that make geophysical/geochemical modelling difficult. Petrologic/geochemical studies of rift volcanics do not provide unique solutions for our understanding of rift environments. Detailed stratigraphic/structural analysis of individual rifts are still the best methods for rift analysis.
Thermal structure and kinematics of mid‐oceanic ridge axis, some implications to basaltic volcanism
Authors: Sleep Norman H.
Published: February 2008

Studies of ophiolitic complexes and thermal and mechanical speculations indicate a highly complex history of basaltic magmas at mid‐ocean ridges. A thin molten region about 3 km wide probably exists at the top of the magma chamber. Primitive material enters the uppermost part of the chamber from below. Fractionated material is removed by the upward extrusion of dikes and settling of crystals to form a mush which probably fills the bulk of the chamber. The roof of the magma chamber is probably cooler than the melting temperature of primitive basalt. Secondary melts are probably produced most voluminously in the cumulate mush and also at the distal ends of the magma chamber and the bottom portions of dikes which cannot immediately solidify. The volume of the uppermost molten region can in principle be determined from chemical heterogeneities in basalts over a limited area and time. For mechanical reasons, the volume of additions of material from below is comparable to the volume of crustal dikes. Weaknesses along the line of dike intrusion and limited plating of material onto the roof of the chamber may restrict dike intrusion to the exceeding narrow zone inferred from ophioltic complexes.
Morphometric evolution of composite volcanoes
Authors: Wood Charles A.
Published: February 2008

Statistical relations have been determined between geometry, volume, slope, and age for 26 circum‐Pacific composite (strato) volcanoes. General trends in eruption characteristics, repose periods, flow lengths, and petrology are also documented. Few examples of the earliest stages of composite volcano activity are known, perhaps because these small volcanoes are indistinguishable from cinder cones. If cinder cones evolve into composite volcanoes a fundamental change in morphometry, eruption style, and petrology occurs at a basal diameter of 2 km.

Composite volcanoes (stratovolcanoes), composed of layered deposits of pyroclastics and lavas, are the characteristic volcanic landform at sub‐ducting plate margins, and are the most abundant type of large volcano on the Earth's surface. Composite volcano morphology results from repeated eruptions of pyroclastics and relatively short lava flows from a central vent. By comparison, pyroclastics are insignificant and lava flows tend to be much longer (10‐100 km) for shield volcanoes. Most composite cones are formed of andesites or basaltic andesites, but some are composed of basalts (Fuji, Fuego, Izalco); thus petrology may be less important in determining the morphology of composite cones than eruption style, as is true for shield volcanoes (Wood, 1977a). In this study, observations of eruption characteristics and chemical/petrological trends for a number of composite cones were synthesized with newly determined measurements of cone morphology to document statistically the evolution of composite volcanoes and to examine their relation to cinder cones. Additionally, such quantitative descriptions of terrestrial volcanoes provide basic data for comparisons with volcanic structures on Mars and the Moon.
The redox state of planetary basalts
Authors: Haggerty Stephen E.
Published: February 2008

A well established data base exists for the oxidation‐reduction (redox) states of basalts on the Earth and on the Moon; the former equilibrate along the fayalite‐magnetite‐quartz buffer curve, and the latter crystallize in the field of metallic iron stability, below the iron wustite buffer. Preferred accumulation of volatiles and the disproportionation of water into hydrogen and oxygen in thick terrestrial lavas and in ponded lava lakes results in high states of oxidation equivalent to that of hematite stability. At the other extreme, lunar basalts exhibit the effects of subsolidus reduction and estimates yield T = 700‐1000°C and fO2 = 10−16 to 10−23 atms. Based on a number of cosmogenic properties, models for planetary interiors, and the sequence of condensation with heliocentric distance from the protosun, estimates for the redox states of inner solar system planetary basalts yield the following results: Basalts on Mercury and the Moon crystallize below the iron‐wustite buffer curve; Venusian basalts are more oxidized than those on Mercury, less oxidized than those on Earth, and crystallization within the field of wustite stability is suggested; basalts on Earth are dominantly in the field of magnetite stability in close proximity to the fayalite‐magnetite‐quartz buffer curve; Martian basalts are estimated to crystallize in the upper regions of magnetite stability and well into the hematite field of stability expressed in terms of temperature and oxygen fugacity.
Multi‐harmonic electron cyclotron instabilities
Authors: Ashour‐Abdalla M. , Kennel C. F.
Published: February 2008

We present parametric studies of the loss cone instability of multi‐harmonic electron cyclotron instabilities in a plasma consisting of a hot component with loss cone free energy source and a cold thermal component. We find that the cold upper hybrid frequency must exceed the wave frequency in order that a non‐convective instability exist. When NC/NH ∼ 0.5, at least the first three harmonic bands can be simultaneously non‐convective. However, the first harmonic band has large spatial growth rates over the widest parameter range; it should therefore be the most commonly observed harmonic, and except in certain circumstances should normally accompany the higher harmonics when they are observed.
Lunar Mare versus terrestrial mid‐ocean ridge basalts: Planetary constraints on basaltic volcanism
Authors: Papike J. J. , Bence A. E.
Published: February 2008

Major differences which exist between terrestrial midocean ridge basalts (MORB’s) and lunar mare basalts reflect the different planetary characteristics of Earth and Moon. MORB’s are enriched in aluminum and have higher Mg/(Mg + Fe²+). These features reflect a more aluminum and magnesium‐rich mantle source for MORB’s. Mare basalts are depleted in sodium and potassium relative to MORB’s and, consequently, mare feldspars are depleted in the albite component relative to MORB feldspars; these features are a reflection of the alkali depleted nature of the Moon relative to the Earth. The oxygen fugacities that obtained during MORB petrogenesis follow the quartz‐magnetite‐fayalite buffer curve very closely while those of mare basalts are several orders of magnitude lower. This results in reduced valence states for Fe, Cr and Ti in mare basalts, which, in turn, has a significant effect on mineral‐melt partitioning.
Simultaneous measurements of energetic protons and electrons in the distant magnetosheath, magnetotail, and upstream in the solar wind
Authors: Krimigis S. M. , Venkatesan D. , Barichello J. C. , Sarris E. T.
Published: February 2008

Measurements of energetic protons (Ep > 0.29 MeV) and electrons (Ee ≳ 0.22 MeV) in the magnetopause/magnetosheath region of the tail and simultaneously upstream from the bow shock in the solar wind using data from JHU/APL instruments on the IMP‐7 and IMP‐8 spacecraft during December 9 to 14, 1974 are reported. Similar fluxes of protons and electrons exhibiting extreme time variation were found to be present simultaneously in the solar wind and the distant (≳ 30 Re) magnetopause/magnetosheath during this period. Protons and electrons were streaming in the antisolar direction in the magnetosheath, with the protons exhibiting much larger tailward‐to‐sunward anisotropies (maximum values of ∼ 700∶1 compared to ∼ 9∶1 for protons and electrons, respectively). The ratios of energy densities of protons‐to‐electrons ranged from ∼ 500 to ≳ 2000 in the magnetosheah, during selected time intervals. Protons and electrons upstream were moving sunward away from the bow shock. Additional measurements on September 11‐12, 1975 in the magnetosheath and inside the magnetotail show proton and electron intensities to be much larger (up to ∼ × 10) inside the magnetotail. The observations are interpreted as a temporal rather than spatial phenomenon, the source of the particle bursts being inside the magnetosphere. It is concluded that there is no connection between the presence of energetic particles in the tail magnetopause/magnetosheath and the postulated energy release via field line merging at the subsolar magnetopause.
Thermal excitation of atmospheric tides due to insolation absorption by O3 and H2O
Authors: Forbes Jeffrey M. , Garrett Henry B.
Published: February 2008

The thermal excitation of diurnal and semidiurnal tidal modes due to insolation absorption by O3 and H2O is investigated. Significant structural and seasonal differences from the heating profiles given by Chapman and Lindzen (1970) are reported.
Hydroxyl and peroxy radicals in polluted tropospheric air
Authors: Hov Øystein , Isaksen Ivar S. A.
Published: February 2008

Model calculations show that hydroxyl is a rather conservative specie with respect to abundance and diurnal variation. Calculated maximum concentrations range from about 6×10−5 to 4×10−4 ppb for winter and summer, clear and clouded sky, temperatures ranging from 0 to 25°C and pollutant emissions ranging from average values for Western industrialized countries to urban areas. Peroxy radicals show a much stronger variability in concentration partly due to their strong dependence on NO. Gas phase sulfate conversion rates up to 3% hr−1 are calculated. Sulfate and ozone are efficiently generated in moderately polluted air.
Measurements of tropospheric and stratospheric H2CO by an infrared high resolution technique
Authors: Barbe Alain , Marché Pierre , Secroun Claude , Jouve Pierre
Published: February 2008

Formaldehyde, H2CO, has been detected in the atmosphere at 2807 and 2869 cm−1 using high resolution infrared absorption spectroscopy from a ground based station. An order of magnitude measure of the column concentration (5 × 1015 molecules per cm²) is given, and an estimate of the trospospheric and stratospheric concentrations is derived from the line pressure broadening.
Earthquakes along the passive margin of eastern Canada
Authors: Stein Seth , Sleep Norman H. , Geller Robert J. , Wang Shi‐Chen , Kroeger Glenn C.
Published: February 2008

An active seismic zone extends along the passive margin of eastern North America from Baffin Island to the Grand Banks of Newfoundland. We have determined the focal mechanisms of several of the earthquakes, including the 1933 Ms 7.3 Baffin Bay earthquake, the largest event ever recorded along the eastern North American margin. The mechanisms show thrust faulting for earthquakes seaward of the 1000 m contour, and primarily normal faulting for earthquakes landward. We propose that these earthquakes are induced by the removal of the Pleistocene glacial loads which extended onto the continental shelf. The deglaciation reactivated basement faults remaining from rifting associated with the opening of the Labrador Sea. Baffin Bay and the Atlantic. A simple flexure calculation yields horizontal extension (normal faulting) in the previously glaciated region, and horizontal compression (thrust faulting) farther seaward, in good general agreement with the observed earthquake mechanisms. The magnitude of the stresses, 100 to 150 bars, is sufficient to reactivate preexisting basement faults. Large passive margin earthquakes may occur as far south along the coast as glaciation extended.
The Moho as a magnetic boundary
Authors: Wasilewski Peter J. , Thomas Herman H. , Mayhew M. A.
Published: February 2008

Mantle derived rocks — peridotites from St. Pauls rocks, dunite xenoliths from the Kaupulehu flow in Hawaii, as well as peridotite, dunite, and eclogite xenoliths from Roberts Victor, Dutoitspan, Kilbourne Hole, and San Carlos diatremes — are weakly magnetic at room temperature. Saturation magnetization values range from 0.013 emu/gm to <0.001 emu/gm equivalent to ∼0.01 to 0.001 wt % Fe3O4. A review of pertinent literature dealing with analysis of the minerals in mantle xenoliths provides evidence that metals and primary Fe3O4 are absent, and that complex Cr, Mg, Al, Fe spinels dominate the oxide mineralogy. These spinels would be non‐magnetic at mantle temperatures. The crust/mantle boundary can be specified as a magnetic mineralogy discontinuity. Curie depth estimates from aeromagnetic anomalies do not require a source of magnetization in the mantle. All of the available evidence supports the new magnetic results, indicating that the seismic Moho is a magnetic boundary. The source of magnetization is in the crust and the maximum Curie isotherm depends on the type of magnetic mineralogy and is located at depths which will vary with the regional geothermal gradient.
Energy coupling function and solar wind‐magnetosphere dynamo
Authors: Kan J. R. , Lee L. C.
Published: February 2008

The power delivered by the solar wind dynamo to the open magnetosphere is calculated based on the concept of field line reconnection, independent of the MHD steady reconnection theories. By recognizing a previously overlooked geometrical relationship between the reconnection electric field and the magnetic field, the calculated power is shown to be approximately proportional to the Akasofu‐Perreault energy coupling function for the magnetospheric substorm. In addition to the polar cap potential, field line reconnection also gives rise to parallel electric fields on open field lines in the high‐latitude cusp and the polar cap regions.
A comparison of Pioneer Venus and Venera bow shock observations: Evidence for a solar cycle variation
Authors: Slavin J. A. , Elphic R. C. , Russell C. T.
Published: February 2008

Observations by the Venera 9 and 10 orbiters in 1975‐76 have been used in previous studies to determine the mean location and shape of the Cytherean bow shock. In addition it has also been reported that the shock is found to be more distant from the planet above regions of the ionosheath where draped IMF field lines are oriented perpendicular to the flow as opposed to parallel. An examination of the dependence of shock altitude in the terminator plane on upstream IMF direction using 86 Pioneer Venus orbiter bow shock crossings in 1978‐79 sets an upper limit on this asymmetry of 12% or approximately half that derived earlier from the Venera data. More significantlythe mean distance to the bow shock observed by Pioneer Venus Orbiter is 35% greater than was the case in 1975‐76 near solar minimum. As the growth in effective obstacle radius is an order of magnitude larger than can be accounted for in terms of varying ionopause altitude due to all causesthese results strongly suggest that Venus can absorb significantly more of the incident solar wind plasma during solar minimum when EUV flux is low than during the current epoch in which maximum is approaching.
Detection of nitrous acid in the atmosphere by differential optical absorption
Authors: Perner D. , Platt U.
Published: February 2008

HNO2 was investigated by long path optical absorption at three sites in Western Europe. It vas definitely identified and measured in moderately polluted air at Jülich. Mixing ratios as high as 0.8 ppb were observed before sunrise. After sunrise the HNO2 is photolyzed and considerable amounts of OH are produced. The formation of HNO2 is unclear and possible reactions are discussed.
Nonlinear stabilization of the current convective instability in the diffuse aurora
Authors: Chaturvedi P. K. , Ossakow S. L.
Published: February 2008

The current convective instability has recently been proposed as a possible mechanism for generating large scale irregularities in the auroral F region, driven by weak field‐aligned currents associated with the diffuse aurora and a plasma density gradient. In this report, we show that this instability can stabilize nonlinearly by generating linearly damped harmonics. An estimate of the saturated amplitudes shows good agreement with the available experimental data. In addition, with a northward plasma density gradient, the dominant nonlinear harmonic is in the northward direction, in agreement with DNA Wideband satellite observations.
Sunward flow in Jupiter's magnetosheath
Authors: Siscoe G. L. , Crooker N. U. , Belcher J. W.
Published: February 2008

The position of Voyager crossings of Jupiter's bow shock show a dependence on solar wind pressure to the −1/3 power. This dependence is used to calculate typical bow shock speeds of 50 km/s from Voyager solar wind plasma data. Since the bow shock and magnetopause move approximately in unison in response to solar wind pressure changes, the resulting movement of the magnetosheath at a sizeable fraction of the solar wind speed leads to reversed, sunward flow in large portions of the dayside region when the boundaries are expanding. Voyager 1 plasma data show evidence of such reversed flow.
Spatial and temporal studies of Jovian kilometric radiation
Authors: Kurth W. S. , Gurnett D. A. , Scarf F. L.
Published: February 2008

Plasma wave measurements taken during the Voyager 1 and 2 Jupiter encounters are used as a basis for synoptic studies of Jovian kilometric radiation. The studies reveal the existence of a shadow zone near the magnetic equator within which kilometric radiation is seldom or weakly observed. This shadow is presumably cast by the Io plasma torus whose density is high enough to refract electromagnetic waves generated either near the torus or closer to Jupiter. At 56.2 kHz this shadow zone has a half width of about 10°. In addition to a latitudinal shadow zone, there occasionally appear to be long‐lived longitudinal variations of kilometric radiation intensities. That is, individual features may reappear on successive rotations at nearly constant System III longitudes. This may imply longitudinally asymmetric structures in the kilometric source region or intervening magnetosphere such as the Io torus which corotate and have lifetimes of up to several days. Some of the features appear to drift to higher longitudes with increasing time suggesting deviations from corotation ranging up to a few percent. Gross changes in the character of Jovian kilometric radiation on time scales of a few days imply dramatic changes in the inner Jovian magnetosphere on the same time scale and may be indicative of magnetospheric substorms or changes in plasma injection rates from Io.
Nitric oxide cooling in the terrestrial thermosphere
Authors: Kockarts G.
Published: February 2008

A simple formulation of the nitric oxide cooling by the emission of the 5.3 µm fundamental band in the terrestrial thermosphere indicates that this process is an important mechanism which has been omitted previously in all thermospheric models. The cooling effect is highly variable as a consequence of its strong temperature dependence and of the observed variability of the nitric oxide concentration. The infrared emission is never in local thermodynamic equilibrium above 120 km altitude and the predominant cooling probably occurs during NO auroral enhancements.
Dobson spectrophotometer total ozone measurement errors caused by interfering absorbing species such as SO2, NO2, and photochemically produced O3 in polluted air
Authors: Komhyr W. D. , Evans R. D.
Published: February 2008

Total ozone measurements made with Dobson spectrophotometers in polluted air are subject to errors caused by interfering trace gas species that absorb solar ultraviolet radiation. While such interference is probably non‐existent or small at the majority of Dobson instrument stations throughout the world, errors of up to 25% and 5%, resulting from absorption by SO2 and NO2 respectively, may occur occasionally at a few stations located in extremely polluted atmospheres. Interference by other absorbers, including N2O5, H2O2, HNO3, acetyldehyde, acetone, and acrolein has been found to be negligible. Ozone produced photochemically in polluted near‐surface air may occasionally constitute from 5% to 10% of the atmospheric total ozone column. Such ozone interferes with measurements of atmospheric background total ozone.
Evidence of gravity waves at E‐region heights
Authors: Giraldez Alberto E.
Published: February 2008

Electron density fluctuations of Sporadic‐E structures lasting several hours without appreciable change in height for days with associated large scale TIDś at F‐Region are under analysis for a latitudinal chain of five ionospheric stations in the South Hemisphere sector. The existence of travelling disturbances at E‐Region affecting Es layers is observed, with propagational velocity towards equator between 250 and 600 m/sec. Power spectra analysis of data shows a few discrete frequencies and a broad band. Comparison of discrete spectra components among stations demonstrate that the wave period grows linearly with distance from the source.
On temperature and speed of He++ and O6+ ions in the solar wind
Authors: Schmidt W. K. H. , Rosenbauer H. , Shelly E. G. , Geiss J.
Published: February 2008

First results on fluid parameters of heavy ions in the solar wind from ISEE‐1 mass spectrometer data are presented. Temperatures and speeds of the He++ and O6+ ions have been determined for about 150 hours of data in late 1977. It is found that the temperatures are roughly proportional to atomic mass of the ion species. When temperatures are comparatively low, this proportionality does not hold for H+. At high speeds and high temperatures the minor ions stream somewhat faster than H+, but there is on average practically no difference between speeds of He++ and O6+.
Postglacial rebound and transient rheology
Authors: Peltier W. R. , Yuen D. A. , Wu P.
Published: February 2008

We consider the possibility that significant effects due to transient creep might conceivably contaminate the measurement of mantle viscosity which one obtains from postglacial rebound data. A time domain mapping is employed which allows us to consider Maxwell and standard linear solids in which the viscosity is time dependent. This technique is used to investigate the impact which either of two recently proposed transient rheologies would have upon inferences of viscosity from isostatic adjustment data. The free decay regime relaxation data from a site near the center of the Laurentide depression (Richmond Gulf) are invoked to show that transient effects, if they exist at all, are most probably weak.