bluuebunny/crossref_metadata_2025 huggingface dataset:
A laboratory study of the λ2145 Å auroral mystery feature
Authors: Erdman P. W. , Espy P. J. , Zipf E. C.
Published: February 2008

The prominent emission feature near λ2145 Å in the ultraviolet spectrum of an aurora has been tentatively identified by Dick [1978] as the doublet lines, λ2139.68 Å and λ2143.55 Å, emitted by metastable N+(5S) ions, and dissociative excitation of N2 by electron impact with a cross section ≥2 × 10−18 cm² has been proposed as the source of this species. A detailed laboratory study of dissociative excitation is described in this letter which suggests two alternative viewpoints of this process: (1) If the calculated radiative lifetime for the N+(5S) state [4.4 µsec] is correct, then the N+(5S) dissociative excitation cross section is <3 × 10−21 cm². Thus, a new N+(5S) source mechanism would have to be found in order to account for the auroral data. (2) If dissociative excitation does form N+(5S) ions efficiently, then the laboratory and field observations imply a radiative lifetime for this state >10 msec, thus suggesting that there are major errors in the lifetime computation.
Influence of the Bx component of the interplanetary magnetic field on magnetopause reconnection
Authors: Gonzalez W. D. , Gonzalez A. L. C.
Published: February 2008

A first clear evidence of an effect of the Bx component (in Solar Magnetospheric Coordinates) of the Interplanetary Magnetic Field (IMF) on magnetopause reconnection has been obtained from polar ionospheric electric fields measured with balloons during an away sector of the IMF. This Bx ‐ effect is such that larger electric field values were measured when Bx was small, and vice versa, during intervals of time with Bz ≤ O, and while the transverse component of the IMF
and the solar wind speed had approximately constant values. For those cases, changes of Bx form 2 to 8 gammas are found to account for as much as a factor of two decrease in the magnitude of the convection electric field at the polar cap. When Bz > O, there is also some indication that the measured dusk to dawn polar cap electric field (reversed convection) became larger when |Bx| was small and vice versa.
A nonlinear mechanism for magnetic reconnection and substorm activity
Authors: Sundaram A. K. , Das A. C. , Sen A.
Published: February 2008

We study the nonlinear effect of a background of microturbulence (in the lower hybrid/ion cyclotron frequency range) on the evolution of a tearing mode instability in the magnetospheric tail region. We find that the linearly stable collisionless tearing modes can be driven unstable by the additional dissipation due to the turbulent fluctuations. The growth times are of the order of 8 to 16 minutes. This mechanism could be important for understanding substorm activity and rapid magnetic reconnection in the tail region.
Implications of solar cycles 19 and 20 geomagnetic activity for magnetospheric processes
Authors: Feynman Joan
Published: February 2008

The solar cycle variations of geomagnetic indices are compared for the last two solar cycles. It is found that the midlatitude aa index and the ring current index, Dst, exhibit a markedly different relationship to one another in the two cycles.

During solar cycle 20 the yearly averaged aa has been shown to be linearly related to either the yearly averaged |Bz| v² or v², where Bz is the north‐south component of the interplanetary field and v is the solar wind velocity. However, the yearly averaged Dst is well represented by a linear function of Bzv and not by a function v². A combination of regression formulas for Dst and aa allows estimates to be made of the annual average v and Bz from 1957 until 1965, when in situ measurements of the solar wind became available. Most interesting, however, is the point that the dependence of aa and Dst on different functions of solar wind parameters implies that the ring current is not directly produced by substorm injections. This result is in agreement with models of magnetospheric processes in which the increased ring current and substorm activity are two separate aspects of increased magnetospheric convection.
Martian climatic change: A magnetic trigger?
Authors: Cordell Bruce M.
Published: February 2008

A new mechanism for climatic change on Mars involving interactions between the atmosphere and a hypothesized ancient planetary magnetic field is suggested and discussed. An early dynamo for Mars is not inconsistent with either current data on the martian interior, models of planet origin, or dynamo theory. The Jacobs/Busse scaling law suggests a martian dynamo field would have effectively shielded the atmosphere from the solar wind. Cooling and/or solidification of the core would cause dynamo extinction and expose the martian atmosphere to the full solar and galactic particle flux. These events may have triggered atmospheric cooling and the present martian frozen surface; as suggested by: (1) climatic records of the earth, and (2) current models of nucleation and other relevant atmospheric processes.
In‐situ measurements of scattering phase functions of stratospheric aerosol particles in Alaska during July 1979
Authors: Grams Gerald W.
Published: February 2008

A laser nephelometer developed for airborne measurements of polar scattering diagrams of atmospheric aerosols was flown on the NCAR Sabreliner aircraft to obtain data on light‐scattering parameters for stratospheric aerosol particles over Alaska during July 1979. Observed values of the angular variation of scattered‐light intensity were compared with those calculated for different values of the asymmetry parameter g in the Henyey‐Greenstein phase function. Our observations indicate that, for the time and location of the experiments, the Henyey‐Greenstein phase function could be used to calculate polar scattering diagrams to within experimental errors for an asymmetry parameter value of 0.49 ± 0.07.
A study of crustal and upper mantle structure of northwestern Turkey
Authors: Necioğlu Altan , Maddison Bryan , Türkelli Niyazi
Published: February 2008

The crustal thickness and uppermost mantle P wave velocity at several seismic stations in Northwestern Turkey were estimated using the established travel time‐distance relation method. The data suggest a flat layered crust of average thickness 28.4 ± 3.45 km with an average uppermost mantle P wave velocity of 8.05 ± 0.17 km/s. This is similar to results obtained for the North Aegean Sea and suggests a close structural link between the two areas.
Lidar detection of volcanic aerosols in the atmosphere following the Mount St. Helen eruption
Authors: D'Altorio Alfonso , Visconti Guido , Fiocco Giorgio
Published: February 2008

We report lidar measurements of the aerosol content of the atmosphere for the first two months following the volcanic eruption of Mt. St. Helen. The measurements were taken near L'Aquila (Italy) with a lidar system utilizing a 50cm diameter telescope. The measurements are compared to similar data for the previous quiescent period and show a large increase of the backscattering ratio in the stratosphere and upper troposphere. Layers have been observed at various altitudes. A strong layer at 10‐14Km has been observed only initially. Layers between 14‐25Km have been observed continually. These features show a considerable day to day variability.
Precipitation of energetic neutral hydrogen atoms at Arecibo during a magnetic storm
Authors: Tinsley Brian A. , Burnside Roger G.
Published: February 2008

The production of ionization at upper E region levels at Arecibo and other low latitude sites during magnetic storms had been previously found to be associated with a few rayleighs of N2+ 4278Å emission, but it had not been possible to decide between energetic electrons, ions or neutrals as the primary particles involved.

Observations of H Balmer β emission during such an event now demonstrate that energetic hydrogen atoms or protons are involved. Of these, H atoms from charge exchange of ring current protons are the more plausible explanation. Smaller contributions to the ionization and N2+ emission by other species may be present, and larger contributions to energy deposition by precipitating oxygen are probably present.
Jupiter's magnetopause, bow shock, and 10‐hour modulated magnetosheath: Voyagers 1 and 2
Authors: Lepping R. P. , Burlaga L. F. , Klein L. W.
Published: February 2008

This summary report discusses Jupiter's magnetopause, bow shock and magnetosheath, based on fine scale magnetic field data from the Voyager 1 and 2 encounters. Explicit models of the dawnside magnetopause and bow shock in Jupiter's orbital plane employ an axisymmetric parabola and hyperbola, respectively, and satisfy average boundary crossing positions, inbound and outbound; these models are determined separately for the two encounters. Average magntopause normals, estimated by minimum variance analyses of the field, generally satisfy the model‐parabola to within a few degrees, except for the voyager 2 outbound crossings. A new phenomenon has been discovered in Jupiter's magnetosheath. It is manifested as (5 or) 10 hour quasi‐periodic modulation of the direction of the magnetic field in the outbound magnetosheath, predominantly in the northward (N) and southward (S) directions. It was seen to occur during both encounters and appears most evident in Voyager 2 outbound observations. The durations of the N ⇄ S transitions range from tens of minutes to ∼ 3 hours. These transitions occur in a plane parallel to the local model magnetopause location. These signatures may be due to magnetosheath field line draping modulated by the large scale motion of the magnetospheric plasma disk.
On the parametric dependences of the beam‐plasma‐discharge at low pressures and magnetic field strengths
Authors: Cuperman S. , Roth I.
Published: February 2008

An explanation for the relationship between the critical current and the physical parameters observed in recent experiments on beam‐plasma‐discharge at low pressures and magnetic fields is proposed. The observed relationship is reproduced by combining the threshold condition for electrostatic instability in a magnetized, bounded beam‐plasma system and the balance equation for the rate of plasma production and that of loss through the ends. It is found that the principal scaling of the threshold criterion with variations in the magnetic field is determined by the variations in the radius of the beam‐plasma system.
Paleomagnetism and age of Mafic Plutons, Wichita Mountains, Oklahoma
Authors: Roggenthen William M. , Fischer Joseph F. , Napoleone Giovanni , Fischer Alfred G.
Published: February 2008

A paleomagnetic reconnaissance (43 samples) of the Raggedy Mountain Gabbro Group, which is comprised of a layered complex of anorthosites, anorthositic gabbros, and massive gabbro, shows: (1) stable remanent magnetization and (2) consistent directions which differ significantly from those of the nearby Cambrian Wichita Granite Group, with exception of one site near the granite contact. These results suggest a Precambiran age for the gabbro group. The difference in pole positions between the granitic and mafic groups demonstrates that the plutonic episodes responsible for the mafic and granitic magmas are significantly separated in time. Models of formation of the Wichita aulacogen should be altered to account for the difference in time between the mafic and silicic plutonism.
Correlation of groundwater radon anomalies with earthquakes in the Greater Palmdale Bulge Area
Authors: Teng Ta‐liang , Sun Liang‐fang , McRaney John K.
Published: February 2008

Recent measurements in the Central Transverse Ranges of southern California suggest possible correlations of changes in groundwater radon content with occurrences of nearby earthquakes. Since measurements began in 1974, three radon anomalies have been accompanied by subsequent nearby seismic events. Two of these anomalies were associated with moderate‐sized earthquakes and one with a swarm. Within a 60‐day window prior to the seismicity, groundwater radon increased in each case at sites close to the earthquake epicenters. Before the Big Bear earthquake of June 30, 1979 (M=4.8), radon anomalies were found at three nearby monitoring sites. Groundwater radon content at one site near the January 1, 1979 Malibu earthquake (M=5.0) showed negative as well as positive anomalies both prior to and following the earthquake. A radon anomaly occurred at a nearby spring prior to the fall 1976 Palmdale swarm. The observed pattern is similar to pre‐earthquake anomalies reported from Russia, China and Japan.
Uranium concentrations and 234U/238U activity ratios in fault‐associated groundwater as possible earthquake precursors
Authors: Finkel R. C.
Published: February 2008

In order to assess the utility of uranium isotopes as fluid phase earthquake precursors, uranium concentrations and 234U/238U activity ratios have been monitored on a monthly or bimonthly basis in water from 24 wells and springs associated with Southern California fault zones. Uranium concentrations vary from 0.002 ppb at Indian Canyon Springs on the San Jacinto fault to 8.3 ppb at Lake Hughes well on the San Andreas fault in the Palmdale area. 234U/238U activity ratios vary from 0.88 at Agua Caliente Springs on the Elsinore fault to 5.4 at Niland Slab well on the San Andreas fault in the Imperial Valley. There was one large earthquake in the study area during 1979, the 15 October 1979 M=6.6 Imperial Valley earthquake. Correlated with this event, uranium concentrations varied by a factor of more than 60 and activity ratios by a factor of 3 at the Niland Slab site, about 70 km from the epicenter. At the other sites monitored, uranium concentrations varied in time, but with no apparent pattern, while uranium activity ratios remained essentially constant throughout the monitoring period.
Interpretation of a hydraulic fracturing experiment, Monticello, South Carolina
Authors: Narasimhan T. N. , Palen W. A.
Published: February 2008

Pressure transient data from a hydraulic fracturing experiment have been analyzed using a numerical model. Several system parameters and their sensitivities were evaluated, assuming a vertical, penny‐shaped fracture geometry. Although the best‐fit parameters may not constitute a unique set, they do appear credible from what current field experience would indiate. It was found that the injection pressure transient is sensitive to initial fracture aperture, fracture stiffness, minimum horizontal stress, rock toughness, and host‐rock permeability.
Postseismic rebound due to creep of the lower lithosphere and asthenosphere
Authors: Cohen Steven C.
Published: February 2008

Postseismic surface deformations are attributed to the inelastic flow of the subcrustal regions of the earth following an earthquake. A multilayer representation of the earth's rheological properties is used in conjunction with a finite element computational scheme to calculate time‐dependent displacements and strains subsequent to a strike‐slip earthquake. The deviatoric stress‐strain relation for the uppermost layer is assumed elastic. Lower layers are assumed to be, in order of increasing depth, a standard linear, three‐element, viscoelastic solid; a linear viscoelastic fluid; and another elastic solid. Physically these layers correspond to the upper lithosphere, lower lithosphere, asthenosphere, and lower mantle, respectively. Elastic dilatational properties are assumed throughout. Appreciable postseismic displacements, possibly approaching meters for large earthquakes, arise from the viscoelastic relaxation following the sudden coseismic slip. Furthermore, compared to the simpler case of an elastic lithosphere over a viscoelastic asthenosphere the near‐fault postseismic shear strain is increased, by a factor of two or more in some cases, by the presence of a viscoelastic lower lithosphere. Also the duration of postseismic straining is increased if the viscosity of the lower lithosphere is greater than that of the underlying asthenosphere.
Observations of the far ultraviolet nightglow
Authors: Paresce Francesco
Published: February 2008

The extreme ultraviolet telescope on the Apollo‐Soyuz mission observed the far UV nightglow in the 1350‐1700 A band from an altitude of 225 km at solar minimum in July 1975. Looking down when the spacecraft was clear of the auroral zones, a faint glow well above instrumental background and varying smoothly with solar zenith angle is recorded. The minimum intensity at solar zenith angles >150° is ≈100 photons cm−2 s−1 sr−1 A−1 (≈ 0.2 Rayleighs) in this passband and is most probably due to N2 Lyman‐Birge‐Hopfield band emission. Looking up, the airglow, if it exists, is very difficult to disentangle from the astronomical background, except in one case where an obvious equatorial enhancement of ≈ 1000 photons cm−2 s−1 sr−1 A−1 is observed. The measured intensities looking down are in all cases substantially less than those reported by Huffman et al. [1980] and consistent with upper limits established in 1968 by Prinz and Meier [1971]. Thus the enhancements observed by Huffman et al. must be due either to an impulsive short‐lived source or to a secular increase since 1975 of one or more of the parameters affecting the unknown emission mechanism.
Strain and displacement measurements for the June 9, 1980 Victoria, Mexico Earthquake
Authors: Darby D. , Nyland E. , Suarez F. , Chavez D. , Gonzalez J.
Published: February 2008

A microgeodetic network 22 km south east of Est. Guadalupe Victoria, Baja California Norte, installed in late May 1980, has been resurveyed in an experiment that started 12 hours after the June 9, 1980 Victoria earthquake, which had an epicenter at 10 km depth about 12 km from the network. The resurvey was complete by June 13. Both the initial observations and the resurvey were done with HP3800 distance meter equipment. Some angular control was provided with a Wild T3 theodolite. The network underwent a compressive strain of 7 ± 3 micro strain essentially parallel the Cerro Prieto fault about the time of the earthquake. Strains of this size are associated with simple dislocation models of earthquakes of this magnitude. Its direction appears to be anomalous however. This may indicate compression related to soil liquefaction processes or strain near the end of the slip plane.
Factors in the design and manufacture of large high pressure and high temperature triaxial cells
Authors: DuBois Andrew
Published: February 2008

Factors important to the design of vessels for testing the physical and hydraulic properties of rock samples of the order of one meter diameter by three meters long are discussed. The stored energy of water and nitrogen gas pressurized at 60 MPa and 200° C are shown to be comparable. Some constraints imposed by heating needs, vessel material selection, cell geometry, materials handling, and safety are reviewed.
On physical modeling of rock
Authors: Cheney James A.
Published: February 2008

The problems of satisfying similarity between a physical model and the prototype in rock wherein fissures and cracks place a role in physical behavior is explored. The need for models of large physical dimensions is explained but also testing of models of the same prototype over a wide range of scales is needed to ascertain the influence of lack of similitude of particular parameters between prototype and model. A large capacity centrifuge would be useful in that respect.
Non‐thermal equilibrium between electrons and neutrals at ionospheric E‐region heights
Authors: Duhau S. , Azpiazu M. C.
Published: February 2008

The results of measurements of electron temperature in the E‐region by incoherent scatter radar and Langmuir probes are contradictory. To provide an additional empirical evidence a correlation is found between the collision frequency data obtained by the method of deviative absorption and F10.7 (for a height of 110 km) at noon. A remarkable agreement is found between these results and those obtained with the collision frequencies calculated from temperatures measured with probes on quiet days. We conclude that, contrary to what is usually assumed, electrons and neutrals are not in thermal equilibrium in the E‐region, the quotient between the electron and neutral gas temperatures (Te/Tn) depends strongly on F10.7, and that there is a mechanism whereby electrons are heated, totally localized in the E‐region.
Modulation of Venus ion densities associated with solar variations
Authors: Bauer S. J. , Taylor H. A.
Published: February 2008

The dayside ion concentrations in the Venus ionosphere obtained by the Pioneer Venus orbiter ion mass spectrometer exhibit a modulation corresponding to the 27‐day solar variation. Comparisons were made of the amplitudes of modulation of CO2+, C+, and O2+, with the amplitudes of the 27‐day variation in the 10.7 cm solar radio flux and the simultaneously measured EUV fluxes at He II (304A) and Lyman β (1026A), together with a theoretical analysis of the effects of solar variability on the ionosphere and neutral atmosphere of Venus. This analysis leads us to the conclusion that the observed modulation of dayside ion densities is primarily due to the variability in the ionizing EUV radiations and, to a much lesser extent, the result of the variability with solar activity of the neutral atmosphere via the variability in exospheric temperature. In this connection, we also show, theoretically, why the percentage variation of exospheric temperature on Venus (as observed in the ONMS data) for a given variation in F10.7, is only half of the exospheric temperature variation for Earth.
Boundary forces and plate velocities
Authors: Carlson Richard L.
Published: February 2008

The notion that plate motions result from forces associated with plate boundaries implies that average plate velocities in a mantle (hot spot) frame of reference are systematically related to the nature and geometry of plate boundaries, and to the proportion of continental lithosphere included in the plates. Several simple, linear models relating plate velocity v to net ridge push (RP), slab pull (SP), trench suction (TS) and continental drag (CD) have been evaluated by multiple linear regression. Ridge push, slab pull and continental drag are found to be vitally important. Trench suction may be a real force, but because effective trench lengths are small and only three of the twelve plates considered are affected, it is not a statistically significant contributor to plate motions.

The preferred relation, v(cm/yr) = (2.7±.4) + (5.2±1.9)RP + (13.2±1.6)SP − (4.7±.6)CD is a remarkably good predictor of average plate velocities, with an rms error of 0.50 cm/yr, and a correlation coefficient of 0.97. The implied balance between these net forces is generally consistent with the results of force‐balance models. The constant term includes all forces not explicitly considered, and suggests that the combined effects of such forces are about equal for all plates. Finally, because the parameters used for any particular plate are independent of all other plates, the success of this simple model strongly suggests that the forces which drive plate motions are intimately related to the plates themselves.
Global atmospheric distribution and trend of methylchloroform (CH3CCl3)
Authors: Rasmussen R. A. , Khalil M. A. K.
Published: February 2008

Over the last two years atmospheric measurements of methylchloroform (CH3CCl3) have been made at six locations using EC/GC techniques. The concentrations are reported, and it is shown that CH3CCl3 concentrations increased at rates of 3.8%±2.1% per year at Alaska (∼70°N) between 8/79 and 1/81, 6.6%±3.2% per year at Oregon (∼45°N) between 1/79 and 1/81, 4.3%±4% per year at Hawaii (24°N) between 11/79 and 1/81, 4.1%±4.8% per year at Samoa (14°S) between 2/80 and 1/81, 11.5%±1.5% per year at Tasmania (42°S) between 1/79 and 6/80, and at 8.7%±5.7% per year at the south pole between 1/79 and 1/81. These recent yearly increases are smaller than earlier rates of increase but are consistent with a lifetime of ∼7 years (6 years‐10 years) and a decline in the rate of global emissions.
Comments on “A meteor‐ablation model of the sodium and potassium layers” by D. M. Hunten
Authors: Clemesha B. R. , Kirchhoff V. W. J. H. , Simonich D. M.
Published: February 2008

The published results of lidar observations of the atmospheric sodium layer show that any consistent change in the abundance of sodium during the night is very small, and that there is probably little change between day and night. These measurements also show that the winter increase in sodium observed at mid‐latitudes occurs mainly on the bottomside of the layer. Recent 24‐hour observations show that any 24‐hour component in the diurnal variation in abundance is less than about 5% of the mean. At least as it stands the recently proposed meteor‐ablation model, in which sodium atoms which enter the atmosphere during meteor ablation are lost by ionization and subsequent attachment of the ions to aerosols, is shown to be inconsistent with these experimental data.
Standing waves observed at the dayside magnetopause
Authors: Fahnenstiel Steven C.
Published: February 2008

Energetic (>24 keV) ion distributions are used to remotely sound an ion trapping boundary at the dayside magnetopause for two inbound crossings of ISEE‐2 on days 347 and 312, 1977, at 0830 and 1100 LT. By applying single particle trajectory models to the observed temporal relationships between trapping boundary distance and orientation parameters, we conclude that longitudinal standing waves occur on the boundary, having typical wavelengths of 1500‐3000 km, amplitudes of 500 km, and periods of 200‐400 sec. The standing wave nodes move along the node axis with velocities 1.5 to 6 km/sec. The data are inconsistent with models of traveling waves moving tailward along the boundary.
Finite‐strain equation of state for high‐pressure phases
Authors: Jeanloz Raymond
Published: February 2008

A linear least‐squares fit of a finite‐strain equation of state to pressure‐density measurements is possible even when the initial density is unknown. This provides an objective extrapolation of data on a high‐pressure phase to zero pressure, and the zero‐pressure density and elastic properties (as well as their uncertainties) can be directly estimated. For typical uncertainties in ultrahigh pressure diamond‐cell experiments, compression data extending over strains of the high‐pressure phase of at least 0.04 and 0.11 (i.e., compression ranges, Δρ/ρ, of at least 12% and 35%) are required in order to constrain, respectively, third‐ and fourth‐order contributions to the equation of state.
Externally driven magnetic reconnection versus tearing mode instability
Authors: Sato Tetsuya , Hasegawa Akira
Published: February 2008

Theoretical estimate as well as numerical simulations show that while a resistive tearing mode instability saturates at a low flow velocity, an externally driven reconnection, however weakly driven, brings a new nonlinear state with strong plasma jet which squeezes out tearing mode driven magnetic islands. This result suggests that the externally induced reconnection is the more likely candidate for explosive phenomena such as magnetospheric substorms and/or solar flares.
Electrostatic plasma instabilities in the daytime lower ionosphere
Authors: Basu B. , Chang Tom , Jasperse J. R.
Published: February 2008

Using a model collision operator we derive the dispersion relation for high frequency electrostatic waves in the lower ionosphere for daytime, midlatitude conditions. We find that the suprathermal electrons near 5 eV can excite unstable electron cyclotron and upper hybrid waves. The possible role of these instabilities in determining the shape of the photoelectron energy spectrum from 2 to 6 eV is briefly discussed.
The equation of state of Mg0.6Fe0.4O to 200 GPa
Authors: Vassiliou M. S. , Ahrens Thomas J.
Published: February 2008

New Hugoniot data on polycrystalline (avg.porosity 6.9%) samples of the magnesiowustite Mg0.6Fe0.4O are presented, covering the pressure range up to 200 GPa. When our data are fit by a single 3rd order Eulerian Hugoniot with KO constrained to its ultrasonic value of 161.5 GPa, the required isentropic pressure derivative KO′ is 4.37 +/− 0.37. This value is significantly lower than the ultrasonic one of 6.18; existing isothermal compression data, however, are in agreement with our value rather than the ultrasonic one. Our data are adequately explained without phase transitions. There is some marginal evidence for a possible phase transition around 120 GPa. If such a transition indeed occurs it is probably of small volume change compared to the transition observed in FeO; we place an extreme upper bound of 3% on the density change such a transformation could involve and still be consistent with the data. Contrary to earlier hypotheses, we believe that a phase transition in magnesiowustite is not a likely explanation of the seismic effects in the D″ region of the lower mantle. The wustite transition may be a more complex phenomenon than initially supposed— perhaps an effect of nonstoichiometry localized to the iron‐rich end of the solid solution series.
Simulation of the October 23,1980 stratoprobe flight
Authors: Evans W. F. J. , McElroy C. T. , Kerr J. B. , McConnell J. C.
Published: February 2008

Measurements of ozone, water vapour, nitric acid and nitrogen dioxide taken during the STRATOPROBE flight of October 23, 1980 from Palestine Texas at 32°N are presented. The measured ratio of HNO3 to NO2 is in good agreement with that of a one dimensional model using current photochemistry. The measured ratio is used to infer "proxy" hydroxyl densities. These OH densities are very low below 25 km, in agreement with the findings of earlier flights.
Magnetic charts of Canada derived from MAGSAT data
Authors: Newitt L. R. , Dawson E. , Coles R. L. , Nandi A.
Published: February 2008

To evaluate the use of scalar and vector Magsat data for the production of regional magnetic charts, comparisons have been made between charts of the north, east, vertical and total fields derived from Magsat with those derived primarily from Canadian aeromagnetic data. Approximately 12000 satellite data were reduced to sea‐level using the spherical harmonic model MGST (4/81). Approximately 9900 aeromagnetic data from 1959 to 1976 were also reduced to sea‐level and updated to 1980. All data were gridded at 1deg; intervals of latitude and longitude, and charts contoured.

Good agreement exists between charts produced from the two data sets; the overall rms difference is 150 nT. The poorest agreement occurs in the north component. In all components the largest differences occur in the northern United States and along the east coast of Canada. Over the rest of the map area there are only a few large, randomly distributed differences.
MAGSAT magnetic anomalies over Antarctica and the surrounding oceans
Authors: Ritzwoller Michael H. , Bentley Charles R.
Published: February 2008

A procedure to select and reduce satellite magnetic anomaly data in high southern latitudes is described, and a map of Antarctica, constructed using this procedure, is shown. The map is qualitatively analyzed for error and geologic significance. Correlations are noted between magnetic anomalies and mountain ranges, subglacial basins, tectonic provinces, regional gravity anomalies, a hypothetical continental rift feature, oceanic basins, and oceanic rises. Overall, the correlation between the magnetic anomaly patterns and known geological features is good.
MAGSAT scalar anomalies and major tectonic boundaries in Asia
Authors: Frey Herbert
Published: February 2008

The distribution of MAGSAT scalar anomalies is compared with locations of major tectonic boundaries in Asia. Foldbelts separate large‐scale positive and negative anomalies inside and outside the Siberian Platform, and sediment‐filled aulacogens within the Platform separate the anomalies into two parts which overlie the Anabar and Aldan Shields. Tectonic boundaries appear to exercise some control over the extent and distribution of the satellite‐observed crustal anomalies.
An equivalent layer magnetization model for the United States derived from MAGSAT data
Authors: Mayhew M. A. , Galliher S. C.
Published: February 2008

Long wavelength anomalies in the total magnetic field measured by Magsat over the United States and adjacent areas are inverted to an equivalent layer crustal magnetization distribution. The model is based on an equal area dipole grid at the Earth's surface. Model resolution, defined as the closest dipole spacing giving a solution having physical significance, is about 220 km for Magsat data in the elevation range 300‐500 km. The magnetization contours correlate well with large‐scale tectonic provinces.
Regional magnetic and gravity anomalies of South America
Authors: Hinze W. J. , von Frese R. R. B. , Longacre M. B. , Braile L. W. , Lidiak E. G. , Keller G. R.
Published: February 2008

Preliminary satellite scalar magnetic anomaly data (MAGSAT) reduced to vertical polarization and long‐wavelength‐pass filtered free‐air gravity anomaly data of South and Central America are compared to major tectonic features. A number of correlations are observed, but these must be generalized because of the preliminary nature of the geophysical data and the inherent petrophysical variations within tectonic features. Statistical analysis of the magnetic data reveals that South and Central America are more magnetic and magnetically more variable than adjacent marine areas. More obvious correlations exist between magnetic anomalies and tectonic elements of the continents than in the case of oceanic areas. No obvious correlations occur between the tectonic features of the Atlantic Ocean, including the Mid‐Atlantic Ridge, and magnetic anomalies. The continental shields generally are more magnetic than adjacent basins, oceans and orogenic belts. In contrast, the major aulacogens are characterized by negative magnetic anomalies. Positive free‐air gravity anomalies are related to the Andean Foldbelt, but the relationship of this feature to magnetic anomalies is much less obvious. However, along the west coast of South America, the magnetic anomalies of the Pacific Ocean are separated from those of the eastern platforms by north to northwest trending anomalies. South of the equator along the Foldbelt, gravity maxima are related to magnetic minima, a relationship analogous to the situation observed in the Rocky Mountain Cordillera. North of the equator in Columbia, gravity and magnetic maxima roughly correlate along the Foldbelt.
A satellite magnetic model of northeastern South American Aulacogens
Authors: Longacre M. B. , Hinze W. J. , von Frese R. R. B.
Published: February 2008

Magnetic modeling of the Amazon River and Takatu Aulacogens in northeastern South America illustrate the utility of satellite magnetic data in characterizing the properties and structure of the lithosphere. Specifically, reduction of preliminary MAGSAT scalar magnetic anomaly data to an equivalent condition of vertical polarization shows a general correlation between magnetic anomaly minima and the Amazon River and Takatu Aulacogens. Surface gravity data demonstrate a correlative positive anomaly. Spherical earth modeling of the magnetic data indicates a less magnetic crust associated with the aulacogens which is compatible with previous studies over the Mississippi River Aulacogen and Rio Grande Rift in North America.
Parameters and a magnitude moment relationship from small earthquakes observed during hydraulic fracturing experiments in crystalline rocks
Authors: Pearson C.
Published: February 2008

Using source parameters estimated from seismic spectra and magnitudes estimated from coda lengths, we demonstrate that the log‐linear relationship between moment and magnitude holds for events with magnitudes as low as −6. Using, as a data set, events induced by hydraulic fracturing experiments at the Fenton Hill, New Mexico, Hot Dry Rock (HDR) geothermal site, we find that the relationship between magnitude M and seismic moment (Mo) is

urn:x-wiley:00948276:media:grl1930:grl1930-math-0001

Moreover, the linear relationship between seismic moment and source radius (r) holds for the Fenton Hill microearthquakes. Analyses of the Fenton Hill data yield the following relationship.

urn:x-wiley:00948276:media:grl1930:grl1930-math-0002
A new method for characterization of downhole antennas used in geophysical probing
Authors: Daily William
Published: February 2008

We have developed a technique for measuring from boreholes the radiation pattern of a high frequency electromagnetic antenna system. Three coplanar holes are required with a single transmitter in one and two identical receiving antennas in the other holes. Signal attenuation is measured along several ray paths at different angles from the source. The method does not depend on the subsurface to be electrically homogeneous but does require reflections and refractions to be negligible. Measurements in fractured granite demonstrate the utility of the technique to obtain antenna radiation patterns. A modification of this same method could be used for characterization of downhole acoustic sources.
The evolution of the Earth's atmosphere and oceans
Authors: Melton Charles E. , Giardini A. A.
Published: February 2008

A model describing the evolution of the present atmosphere and hydrosphere has been developed. The model is based on the following experimental parameters: a) the abundance of mantle fluid occluded in Arkansas diamonds, b) the 3.1 b.y. age of crystallization for an Arkansas (USA) diamond, c) the depth range for diamond formation, about 100 to 400 km and d) the age for the Earth of 4.67 b.y. The data for all occluded fluids except H2O and CO2 are interpreted in terms of a first order mechanism for degassing of the Earth. A rate constant of 6.5 × 10−10yr−1 is obtained which gives good agreement for experimental values of atmospheric N2 and 36Ar. The constant is slightly higher than that for decay of 40K (λ=5.5×10−10 yr−1) and suggests that the decay of 40K might be the main driving force for all processes occurring in this region of the mantle. Evidence indicates that C2 and H2O exist in two phases in the low seismic velocity region of the upper mantle. If true, this requires a transformation of the first order rate law to a zero order rate law for these fluids. This was done and with λH2O = 3.4×108 tons yr−1 and λCO2 = 0.5×108 tons yr−1 the experimental and calculated values agree. Good agreement between the calculated and experimental abundance of all fluids in the atmosphere and hydrosphere gives strong support for the validity of the theoretical model. To preclude possible fortuitous agreement, four additional tests over different time spans were made; one with N2, two with Ar and one with H2O. The experimental results and theoretical values agree to within 20% for these additional tests, further supporting the model.
Solar spectral irradiance, 120 to 190nm, October 13, 1981 ‐ January 3, 1982
Authors: Rottman G. J. , Barth C. A. , Thomas R. J. , Mount G. H. , Lawrence G. M. , Rusch D. W. , Sanders R. W. , Thomas G. E. , London J.
Published: February 2008

Beginning on October 13, 1981 a two channel spectrometer aboard the Solar Mesosphere Explorer has been obtaining daily measurements of full disc solar irradiance. These observations cover the spectral interval 120 to 305nm with ∽ .75nm spectral resolution. The relative accuracy of the measurements from day to day over the first three solar rotations is approximately 1%. In this report we present analyses of Lyman‐alpha, the integrated Schumann‐Runge continuum (130‐175nm), and the integrated Schumann‐Runge bands (175 to 190nm). All three show a clear variability related primarily to the 27‐day solar rotation period. Correlations of these three values of solar irradiance to ground‐based indices of solar activity, 10.7cm flux and sunspot number, are presented.
Altitude variations in stratospheric aerosols of a tropical region
Authors: Goodman Jindra , Snetsinger K. G. , Ferry G. V. , Farlow N. H. , Lem H. Y. , Hayes D. M.
Published: February 2008

To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector.

Percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 µm in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature.

Aerosols containing smaller‐size particles are thus found closer to the tropopause, and larger‐size, more‐evolved aerosols occur at higher altitudes. These data indicate that convective activity at the ITCZ may be a source mechanism for stratospheric aerosols.
An extremal principle for a one‐dimensional climate model
Authors: Lin Charles A.
Published: February 2008

An extremal principle is formulated and applied to a one‐dimensional energy balance model. The principle is based on the maximization of the generation of available potential energy, and reduces to a maximization of the correlation between heating and temperature deviation. The maximization is subject to a constraint of global energy balance, and makes no reference to a dynamical transport mechanism. The maximizing temperature distribution has a larger meridional gradient than the observed temperature distribution. Our results suggest the general circulation operates at nearly its maximum efficiency.
Solar activity and nitrate deposition in South Pole snow
Authors: Laird Claude M. , Zeller Edward J. , Armstrong Thomas P. , Parker Bruce C.
Published: February 2008

For the past 51 years nitrate deposition in snow and firn layers at the South Pole exhibits a significant linear relationship with sunspot numbers and the ‘aa’ index of geomagnetic activity. Currently known atmospheric processes may explain these results. A high resolution nitrate record from deep ice cores could be valuable for both Sun and climate studies.
Ozone absorption coefficients' Role in Dobson instrument ozone measurement accuracy
Authors: Basher Reid E.
Published: February 2008

The differences of 10% or more between the laboratory measurements of UV absorption coefficients by different investigators indicate accuracies that are quite inadequate for current needs in the measurement of atmospheric ozone. The standard band‐integrated set of coefficients now used with the Dobson instrument are mutually consistent to about 2%, but their absolute accuracy is still in question. The accurate calculation of band‐integrated coefficients must take account of their dependence on source spectral irradiance, atmospheric spectral transmittance, mean ozone temperature, and instrument spectral transmittance. A careful examination shows that Komhyr's (1980) case for an error of about +5% in the standard Dobson AD ozone estimation is subject to large uncertainties and certain lacks of independence. The obvious solution to this accuracy problem lies in better laboratory measurements of ozone absorption.
Could the Earth's core and Moon have formed at the same time?
Authors: Andrews D. J.
Published: February 2008

During accretion of the Earth, a layer of liquid iron may have formed above a cold undifferentiated nucleus. Taylor instability of this configuration leads to a deformation with spherical‐harmonic order ℓ = 1, a lower symmetry than assumed heretofore in fission analyses. When this deformation exceeds a few tens of kilometers, strength of the materials becomes insignificant, and the deformation may grow catastrophically, the cold nucleus being displaced laterally at a velocity limited only by inertia. The asymmetric distribution of angular velocity leads to large dynamic pressure in regions of velocity convergence, so that the excess angular momentum of the iron layer may be transferred to a jet of mantle material. Sufficient energy and angular momentum might have been released by core formation to eject material to form the Moon.
Polarization catastrophe model of static electrification and spokes in the B‐ring of Saturn
Authors: Handel Peter H. , James Philip B.
Published: February 2008

An explanation of the charging mechanism operating in the B‐ring of Saturn is offered in terms of a Clausius‐Mossotti type polarization catastrophe based on the peculiar ferroelectric properties of ice. Polarization charges of 400 Coulombs and electrostatic energies of 3 · 109 Joules are estimated.
The importance of ▽B drift in high β magnetospheric plasma instabilities
Authors: Ng P. H. , Patel V. L.
Published: February 2008

The coupling of the shear Alfven wave and the drift compressional wave is studied in a two‐component plasma. It is shown that with the incorporation of ▽B particle drift in the dispersion equation the cold component in addition to reducing the Alfven speed to create an unstable drift compressional wave, also plays an important role in the coupling of the mode to the shear Alfven wave resulting in major modification of the instability.
Properties of seismic wave scattering around water injection well at Fenton Hill hot dry rock geothermal site
Authors: Nishizawa O. , Pearson C. , Albright J.
Published: February 2008

To determine the scattering properties of microcracks created by water injection in hot dry rock a method for analyzing trajectory ellipsoids of seismic particle motions has been applied. Lengths and directions of three principal axes of trajectory ellipsoids were calculated, and a distribution of the shape of these ellipsoids suggests existence of a strong scattering region around the injection point. This strong scattering has an anisotropic property presumably due to microcrack orientation in the original rock.
Survey of a Gulf Stream frontal filament
Authors: Pietrafesa Leonard J.
Published: February 2008

An assortment of data is used to map and characterize a Gulf Stream filament. During 21‐25 April 1980, a filament was captured as it moved through an array of moored current meters on the northeast Florida continental shelf. Current and temperature time series along with satellite VHRR and aircraft ART are used to reconstruct the event. The event is found to consist of an anticyclonically rotating, warm tongue inshore of a cold dome. The rotational scheme of the current in the warm tongue is opposite to previous hypotheses. Upwelling occurs in both the cold dome region and below the warm tongue.
Comparison of mesospheric ozone abundances measured by the Solar Mesosphere Explorer and model calculations
Authors: Solomon S. , Rusch D. W. , Thomas R. J. , Eckman R. S.
Published: February 2008

Ozone observations in the mesosphere obtained by the near infrared and ultraviolet spectrometers onboard the Solar Mesosphere Explorer (SME) satellite are compared to two dimensional model calculations for the month of January. In general, the model calculated abundances are somewhat smaller than those measured, but exhibit similar trends with respect to altitude and latitude. The possible causes of discrepancies include the mesospheric H2O content and photochemical reaction rates, particularly the rate of O2 photolysis.
A second‐order effect of stratospheric vertical motions
Authors: Hunten Donald M.
Published: February 2008

Attention is called to a byproduct of stratospheric motion, distinct from the normal downgradient transport represented by vertical eddy diffusion. An air parcel executes a random walk over a range that could be several kilometers, and similar amplitudes could be present in wavelike oscillations. The photochemical loss rate should therefore be averaged over this range. The effect is proportional to the curvature of the profile of loss rate, and is particularly large for fluorocarbon‐11, CFCl3. Test computations indicate that the known discrepancy between observations and predictions for this compound can be at least partly reconciled for plausible values of the amplitude.