bluuebunny/crossref_metadata_2025 huggingface dataset:
Model simulations of possible electromagnetic induction effects at MAGSAT activities
Authors: Hermance John F.
Published: February 2008

This report uses model simulations to consider two questions: first are magnetic field effects of induced currents flowing in the earth significant for near‐earth satellite observations; second, what are the effects at satellite altitudes of lateral differences in the gross conductivity structure of the earth. For distant sources in the magnetosphere, magnetic fields from electric currents induced in a spherical earth may contribute from 30 to 40% of the external source field amplitude. For near‐earth sources beneath the satellite, e.g. in the ionosphere, the external and internal fields tend to cancel, resulting in a much smaller total horizontal field than would be associated with sources above the satellite. On the other hand, when lateral differences in conductivity are associated with the contact between major geologic units in the lithosphere, local concentrations of induced current may generate unique magnetic field signatures at satellite altitudes. Although the absolute amplitude of the field components may be an order of magnitude smaller than for the case when the source is above the satellite, the magnetic field perturbation measured by the satellite as it crosses the geologic contact is significantly larger in relative terms for ionospheric sources.
The laboratory magnetosphere
Authors: Baum P. J. , Bratenahl A.
Published: February 2008

The UCR 10.9 m long T‐1 terrella facility models collisionless hypermagnetosonic solar wind interaction with a planetary dipole field. Measurements demonstrate that T‐1 has achieved all parameters necessary for limited simulation of the solar wind‐earth interaction. The test time is significantly longer than existing experiments. The first magnetic field map is consistent with Dungey's model in the case of a southward IMF.
Hydromagnetic stability of turbulent geomagnetic tail
Authors: Buti B.
Published: February 2008

The presence of the broadband electrostatic noise, observed in the distant geomagnetic tail by Imp 8, is appropriately incorporated in investigating the hydromagnetic stability of the magnetotail boundary. The observed level of turbulence is sufficient to quench the instability which may be there in the absence of the turbulence. The period of oscillation is in very good agreement with the observed period.
Correlated radon and CO2 variations near the San Andreas Fault
Authors: Shapiro M. H. , Melvin J. D. , Tombrello T. A. , Fong‐liang Jiang , Gui‐ru Li , Mendenhall M. H. , Rice A. , Epstein S. , Jones V. T. , Masdea D. , Kurtz M.
Published: February 2008

Correlations have been observed between groundwater radon and thoron concentrations and carbon dioxide discharges at the Lake Hughes station of the Caltech radon monitoring network. The Lake Hughes site is one of three radon monitoring stations located near the "big bend" segment of the San Andreas fault which began to record anomalous radon levels in August 1981. Two stations, Lake Hughes and Lytle Creek, recorded anomalous increases in radon while the third, Sky Forest, recorded an anomalous decrease. Several weeks after the onset of the anomaly, strongly correlated radon fluctuations began at Lake Hughes and Lytle Creek. These radon spikes also were found to be phase anti‐correlated with barometric pressure fluctuations. Analyses of gas grab samples showed relatively high levels of CO2 and ethylene in borehole air at Lake Hughes and Lytle Creek, while analyses of water samples showed relatively large increases in HCO3− at both sites. Isotopic analysis of one gas sample from Lake Hughes yielded a 13C δ value of −22 ‰, which suggests that the CO2 originates from the oxidation of organic material. The correlation in radon fluctuations at Lake Hughes and Lytle Creek and their common dependence on barometric pressure changes began shortly after the onset of the radon anomaly in August, and probably resulted from the simultaneous saturation of the water in these boreholes with carbon dioxide.
Vertical motions of the neutral thermosphere at midlatitude
Authors: Hernandez G.
Published: February 2008

Determination of vertical motions in the upper thermosphere at midlatitudes from high time resolution Doppler shift measurements of the [OI]³P ‐ ¹D transition emission at night show that there exist oscillations with ∼ 40 min periodicity and large magnitude (ca. 50 m/s). The behavior of these oscillations is ascribed to the passage of gravity waves through that region of the atmosphere. The results also show that individual (high time resolution) zenith measurements of the neutral thermosphere emissions can not be used as (zero) reference winds with any degree of certainty.
Seismic potential of Acapulco‐San Marcos Region along the Mexican Subduction Zone
Authors: Singh S. K. , Espíndola J. M. , Yamamoto J. , Havskov J.
Published: February 2008

Recently, seismic quiescence based on P.D.E. and I.S.C. data, has been reported in the Acapulco‐San Marcos region (16°–17.2°N, 98.5°–99.7°W) (McNally, 1981). In order to assess the seismic potential of this region we have estimated seismic moments and slips associated with 1957 (Ms = 7.5) and 1907 (Ms = 8.0) events which occurred in this area. Historical data suggest that earthquakes occurred in this region in 1845 (Ms ≃ 7.9) and probably also in 1820 (Ms ≃ 7.6). We find preference for the time‐predictable model in the data set which, if valid, forecasts the next large earthquake between now and 1993 with 1985 as the most likely year. Although this forecast can not be taken as definitive since it is based on several assumptions (each of which are reasonable but uncertain), the implications of reported quiescence and the results of this paper suggest a careful monitoring of the area.
Crack fusion dynamics: A model for large earthquakes
Authors: Newman William I. , Knopoff Leon
Published: February 2008

The physical processes of the fusion of small cracks into larger ones are nonlinear in character. A study of the nonlinear properties of fusion may lead to an understanding of the instabilities that give rise to clustering of large earthquakes. We have investigated the properties of simple versions of fusion processes to see if instabilities culminating in repetitive massive earthquakes are possible. We have taken into account such diverse phenomena as the production of aftershocks, the rapid extension of large cracks to overwhelm and absorb smaller cracks, the influence of anelastic creep‐induced time delays, healing, the genesis of "juvenile" cracks due to plate motions, and others. A preliminary conclusion is that the time delays introduced by anelastic creep may be responsible for producing catastrophic instabilities characteristic of large earthquakes as well as aftershock sequences. However, it seems that nonlocal influences, i.e. the spatial diffusion of cracks, may play a dominant role in producing episodes of seismicity and clustering.
Low wavenumber instability on the equatorial beta‐plane
Authors: Boyd John P. , Christidis Zaphiris D.
Published: February 2008

Unstable waves on the equatorial beta‐plane are studied when the mean flow U(y) is a function of latitude only, which permits separation of variables. The additional restrictions of (i) a linear shear U(y) = Sy where S is a constant and y is non‐dimensional latitude and (ii) small zonal wavenumber k permit simple approximations that allow identification of two distinct modes of instability. The "mixed Kelvin‐inertial" mode is an unstable Kelvin wave for |S| < 2 but an inertial instability for larger shear. The "mixed gravity‐Kelvin" mode is the neutral, n=0 positive frequency gravity wave for small shear but an unstable Kelvin wave for |S| > 2. In contrast to normal hydrodynamics problems, there is no minimum shear for instability but instead Im(c) is proportional to exp[−5.34/|S|] for small S. Although the inertial instability was known previously, the two branches of unstable Kelvin waves and the connection between them and the neutral and inertially unstable gravity waves are original discoveries. For weak shear, only the Kelvin wave is unstable.
Composition measurements of warm equatorially trapped ions near geosynchronous orbit
Authors: Quinn J. M. , Johnson R. G.
Published: February 2008

The mass composition of the intense warm (E ∼ 10‐500 eV) ion populations trapped within a few degrees of the geomagnetic equator in the range L = 5.3‐6.5 are examined using data from the Lockheed Ion Mass Spectrometer on the SCATHA spacecraft. The equatorially trapped ions, within the measured energy range E/q ≥ 100 eV, are found to be predominantly protons. These ions can be removed and replenished from the region sampled on time scales shorter than one day. Several recent works have focused on the energization of He+ in the equatorial region by ion cyclotron waves. It is now evident that an energization and/or transport process is required which produces equatorial H+ populations similar to those that have been predicted for He+.
Lower hybrid waves in the solar wind
Authors: Marsch E. , Chang T.
Published: February 2008

We demonstrate that the frequently observed broad band low frequency electrostatic noise in the solar wind generally has a dominant lower hybrid component. These modes are probably produced by the anisotropic halos of the solar wind electron velocity distributions exhibiting "heat flux" profiles and thus, are accompanied by broad band, "hybrid‐like" whistler waves. When the electron temperature is much larger than the ion temperature, these modes can also co‐exist with the ion acoustic waves. Since lower hybrid modes propagate nearly normal to the interplanetary magnetic field lines, the ions can be transversely accelerated by these waves and attain the observed anisotropic and/or loss‐cone‐like distributions.
Aerosol minima
Authors: Hogan A. W. , Barnard S. C. , Winters W.
Published: February 2008

The total number concentration of atmospheric particles, as measured with a variety of Nolan‐Pollak derived photo electric nucleus counters, is often indistinguishable from the concentration measured in filtered air. These periods of near zero aerosol concentration persist for periods of a few minutes to tens of hours at many places.

Near zero concentrations are frequently measured over calm seas following dissipation of fog, but aerosol generation by bubble mechanisms increase the aerosol concentration in a few minutes. Interesting cases of near zero surface aerosol concentration are found over the Arctic in summer when such concentrations persist at the surface for periods of time dependent on sky conditions, surface vegetation and near surface meteorological parameters. Size measurements of the reappearing aerosol indicate that it is formed in situ.
Shot noise from grain and particle impacts in Saturn's ring plane
Authors: Aubier M. G. , Meyer‐Vernet N. , Pedersen B. M.
Published: February 2008

The ring plane event detected by the Voyager 1 and 2 Planetary Radio Astronomy experiment is distinct from Saturn kilometric radiation (SKR) and from Saturn electrostatic discharges (SED). It consists of radio noises recorded only during Saturnian ring plane crossings. Several models are tested. The electrostatic noise on the antennas resulting from the passage of electrons and ions near the antennas (quasi‐thermal noise) leads to order of magnitude much lower than the observed values. Shot noise due to electrons and ions collected and/or emitted by the antennas and spacecraft can explain the noise recorded during Saturn Voyager 1 ring plane crossing and partly what is observed in the case of Voyager 2. For this latter event we must introduce the shot noise due to grain impacts. A quantitative approach of this process gives an estimation of the dust size ∼ 2.3 µm just outside the G‐ring.
Direct observation of radiation belt electrons precipitated by the controlled injection of VLF signals from a ground‐based transmitter
Authors: Imhof W. L. , Reagan J. B. , Voss H. D. , Gaines E. E. , Datlowe D. W. , Mobilia J. , Helliwell R. A. , Inan U. S. , Katsufrakis J. , Joiner R. G.
Published: February 2008

Radiation belt electrons precipitated by controlled injection of VLF signals from a ground based transmitter have been directly observed for the first time. These observations were part of the SEEP (Stimulated Emission of Energetic Particles) experiment conducted during May ‐ December 1982. Key elements of SEEP were the controlled modulation of VLF transmitters and a sensitive low altitude satellite payload to detect the precipitation. An outstanding example of time‐correlated wave and particle data occurred from 8680 to 8740 seconds U.T. on 17 August 1982 when the satellite passed near the VLF transmitter at Cutler, Maine (NAA) as it was being modulated with a repeated ON (3‐s)/OFF (2‐s) pattern. During each of twelve consecutive pulses from the transmitter the electron counting rate increased significantly after start of the ON period and reached a maximum about 2 seconds later. The measured energy spectra revealed that approximately 15 to 50 percent of the enhanced electron flux was concentrated near the resonant energies for first order cyclotron interactions occurring close to the magnetic equator with the nearly monochromatic waves emitted from the transmitter.
Devonian dikes from north central Newfoundland: A radiometric‐paleomagnetic study
Authors: Reynolds P. H. , Murthy G. S.
Published: February 2008

40Ar/39Ar age spectra have been obtained for biotites and hornblendes representing a suite of diabase dikes from the northern part of Newfoundland’s Gander Zone. A primary apparent age of 375 ± 10 Ma is suggested, a value probably very close to the age of intrusion. A number of the age spectra are discordant; this perhaps results from a disturbing ‘event’ ∼180 Ma ago. Magnetic analysis of the dike swarm has yielded four paleopoles; three of these magnetizations appear to be carried by multi‐domain magnetite, the other by hematite. If the magnetite magnetizations are primary, they possibly reflect a period of aberrant geomagnetic field behaviour at about the time given above. On the other hand, if the hematite magnetization is primary, the data can be interpreted in terms of the displaced terrain model of Kent and Opdyke. However, our data imply that the relative southern displacement of Acadia in the Devonian may be smaller than these authors have suggested.
Hall current effect on tearing mode instability
Authors: Terasawa Toshio
Published: February 2008

From a linear 2‐D eigenmode analysis, we found that the Hall current effect on collisional tearing mode instability becomes important for the thin magnetic reversal layer whose width is comparable to the ion inertia length; Hall currents produce a three‐dimensional field structure and increase the reconnection (growth) rate. Since the magnetic reversal layer widths both in the magnetopause and in the magnetotail are reported to become as thin as the ion inertial length (several hundred km) when the reconnection process is supposed to occur, the Hall current effect would have an observational significance. The Hall current effect may explain the appearance of the dawn‐dusk component of the magnetic field in the magnetotail reconnection region.
Large‐amplitude ion bounce wave in the magnetosphere near L=3
Authors: Lanzerotti L. J. , Medford L. V. , Hasegawa A. , Lin D. L.
Published: February 2008

Large amplitude (∼ 30 nT), high frequency (∼0.14 Hz) geomagnetic field oscillations were observed superimposed on lower frequency ones (∼0.008 Hz) at L∼3 during a large magnetic storm. These are the largest amplitude oscillations ever reported in the Pc2 frequency band (0.1 ‐ 0.5 Hz). Measurements at two stations spaced in azimuth by ∼240 km show the higher frequency waves to occur at the same time at both locations. The higher frequency oscillations, which have larger amplitudes at the station closer to local midnight, are consistent with a wave excited by the bounce motion of protons with a peak in the energy distribution at ∼100 keV. The longer‐period variations, which are highly non‐correlated between the two locations, could be evidence of a surface "wave" on the plasmapause.
Paradigm transition in cosmic plasma physics
Authors: Alfvén Hannes
Published: February 2008

During the 1970's in situ measurements in the magnetospheres, including the solar wind region ("solar magnetosphere") drastically changed our understanding of the properties of cosmic plasmas. Further, we have learned how to generalize results from plasma investigations in one region to other regions. This means that laboratory investigations of plasmas of the size of, say, 10 cm can be used to achieve better understanding of cosmic plasmas of magnetospheric dimensions; say, 1010 cm. By another step of 109 we can transfer laboratory and magnetospheric results to galactic plasmas of, say, 1019 cm. A third jump of 109 brings us up to the Hubble distance 1028 cm and hence to cosmological problems (see Figure 1).
Solar irradiance modulation by active regions from 1969 through 1981
Authors: Hoyt Douglas V. , Eddy John A.
Published: February 2008

Recent satellite measurements of the solar total irradiance (S) indicate that on time scales of days to months the solar constant varies by a few tenths of a percent. The predominant part of these variations can be explained by blocking of the upward solar flux by sunspots. The observations are consistent with current theoretical models of energy storage in which the energy blocked by the sunspots is temporarily stored in the convective zone. We present modelled solar constant variations on a day by day basis selected from model calculations for the period 1874 through 1981 (Hoyt and Eddy, 1982). Because neither faculae nor bright rings about sunspots balance the net blocking by sunspots, there is a net eleven year modulation in irradiance with a relative depression of as much as 0.07% for the period 1969‐1981. The model is compared with satellite observations and to other recently published models that impose immediate reradiation of blocked flux and therefore fail to predict an eleven year modulation of S.
Modeling of interaction of artificially released lithium with the Earth's bow shock
Authors: Decker R. B. , Lui A. T. Y. , Krimigis S. M.
Published: February 2008

A numerical simulation is used to predict the interaction between the earth’s bow shock and lithium to be released in the solar wind during the Active Magnetospheric Particle Tracer Explorers program in 1984. Based on the simulation results for a release near the subsolar point, it is recommended that a favorable release condition is when the garden‐hose angle of the interplanetary magnetic field exceeds about 60 to 70° so that the transmission of Li+ ions through the bow shock is optimized. The model also predicts that the Li+ is “shock‐drift” accelerated at the bow shock. The energy gain of Li+ ions is on the average less for the transmitted particles (below a factor of about 4) than for the reflected particles (below a factor of about 16).
Magnetic field fluctuations in the Venus magnetosheath
Authors: Luhmann J. G. , Tatrallyay M. , Russell C. T. , Winterhalter D.
Published: February 2008

Using a model for the convection pattern of the shocked solar wind flow around the Venus obstacle, Pioneer Venus observations of ultra‐low‐frequency (∼10‐40s period) magnetic field fluctuations in the magnetosheath have been traced along streamlines to the region of the quasi‐parallel bow shock. The periods and polarizations of the sinusoidal fluctuations are similar to those observed upstream of the quasi‐parallel bow shock, where streaming superthermal particles are believed to produce MHD waves by a beam‐plasma instability. The results suggest that both disturbances at the ionopause at Venus and the earth's magnetopause may be caused by convection of turbulent magnetic fields from the subsolar bow shock when the interplanetary field direction produces a quasi‐parallel shock there.
Crosshole seismology and seismic imaging in crystalline rocks
Authors: Wong J. , Hurley P. , West G. F.
Published: February 2008

A borehole‐to‐borehole audiofrequency seismic system using piezoelectric transducers as active elements has been developed and used to investigate crystalline rocks in Canada. High‐quality seismograms have been recorded for transmitter‐receiver distances of up to 230 meters. It has been found that both travel times and signal amplitudes provide diagnostic information about rock quality. Two‐dimensional images of seismic velocity and transparency distributions between two boreholes, derived from observed arrival times and amplitudes by simple back‐projection tomography, reflect lithology and geological structure. The results indicate the potential usefulness of crosshole seismic imaging as a tool for rock mass characterization.
A direct comparison of spirit and compensator leveling
Authors: Packard Robert F. , MacNeil John H.
Published: February 2008

Rumpf and Meurisch (1981) conclude that any magnetic field including particularly that of the earth, can deflect the line of sight of compensator or automatic (self leveling) levels. Since the City of Los Angeles has observed many lines of geodetic leveling using a Zeiss Ni‐1 level, a field investigation was designed to assess the potential impact of this error source. The observations were made along a line that had been releveled several times over a period of years. This, generally, north‐south line runs from Tidal 8, San Pedro, to the vicinity of the Jet Propulsion Laboratory in LaCanada (Figure 1). An additional line of leveling was also observed in an east‐west direction. Our investigation seems to confirm the existence of an azimuth dependent error as suggested by Rumpf & Meurisch.
The surface glow of the Atmosphere Explorer C and E satellites
Authors: Langhoff S. R. , Jaffe R. L. , Yee J. H. , Dalgarno A.
Published: February 2008

Detailed line intensities of the rotational‐vibrational spectrum of OH are calculated for various rates of population of sixteen bound vibrational levels in which the rotational level populations are in thermal equilibrium. The line intensities are convolved with the instrument function of the Visible Airglow Experiment on the AE C and E satellites to obtain spectra for comparison with the atmospheric data. Within the uncertainties, a model can be constructed that reproduces the observed spectrum. Synthetic spectra are computed for the OH Meinel system between 2000 Å and 5.5µ. The maximum intensity occurs between 1µ and 2µ.
Temperatures of shock‐induced shear instabilities and their relationship to fusion curves
Authors: Schmitt Douglas R. , Ahrens Thomas J.
Published: February 2008

New emission spectra for MgO and CaAl2Si2O8 (glass) are observed from 430 to 820 nm. Taken with previous data, we suggest that transparent solids display three regimes of light emission upon shock compression to successively higher pressures: (1) characteristic radiation such as observed in MgO and previously in other minerals, (2) heterogeneous hot spot (greybody) radiation observed in CaAl2Si2O8 and previously in all transparent solids undergoing shock‐induced phase transformations, and (3) blackbody emission observed in the high pressure phase regime in NaCl, SiO2, CaO, CaAl2Si2O8, and Mg2SiO4. The onset of regime (2) may delineate the onset of shock‐induced polymorphism whereas the onset of regime (3) delineates the Hugoniot pressure required to achieve local thermal equilibrium in the shocked solid. We also propose that the hot spot temperatures and corresponding shock pressures determined in regime (2) delineate points on the fusion curves of the high pressure phase.
Atmospheric benzene and toluene
Authors: Rasmussen R. A. , Khalil M. A. K.
Published: February 2008

Atmospheric concentrations of benzene (C6H6) and toluene (C7H8) have been observed at nine remote locations of the world ranging in latitude from inside the arctic circle to the south pole. The observations span all seasons at each location. In the northern hemisphere it is observed that C6H6 and C7H8 are most abundant during winter and least abundant during summer. Based on the limited data available, such cycles are not observed in the tropics. These findings are consistent with the expected latitudinal and seasonal variations of OH radicals which cause benzene and toluene to be removed from the atmosphere. The latitudinal distribution shows high concentrations at mid latitudes and low levels in the southern hemisphere. This finding is consistent with the present understanding that the sources of benzene and toluene are primarily anthropogenic. The observed concentration distribution and variability are consistent with the short expected atmospheric lifetime of the order of months for benzene and days for toluene.
Observations of the UV spectrum of Saturn from 3200Å to 1400Å with the IUE
Authors: Moore Vivien , Hunt Garry E. , Caldwell J. , Owen T. , Encrenaz Th. , Combes M.
Published: February 2008

Spectra of Saturn have been acquired with the IUE satellite for the 1400Å to 3200Å wavelength range with, at <10Å, a higher resolution than was previously available. These spectra show the UV reflectivity of Saturn to be highly structured with both resolved and large‐scale absorption features. Model atmospheres constructed for comparison with these spectra included a wavelength dependent UV absorber and the gases PH3, CH4, C2H6, C2H2 and C2H4. Acetylene is identified by a series of resolved absorptions from 1700Å to 1850Å, whereas absorptions from 1700Å to 1610Å may be attributable to ethylene. The IUE spectra provide constraints on the vertical distribution of the atmospheric constituents above the 200 mbar level.
Anisotropy of magnetic susceptibility data indicating remagnetization in diabase dikes
Authors: Ellwood Brooks B.
Published: February 2008

Induced and remanent magnetic analyses have been performed on drilled samples from 2 generations of unweathered diabase dikes, a breccia dike, and the host tonalite which make up the basement on which the Russell Dam foundation was poured. The maximum magnetic foliation plane for most samples, defined by anisotropy of magnetic susceptibility (AMS) data, is vertical and is oriented perpendicular to maximum stresses developed in the region during mid‐late Paleozoic time. The excellent AMS data consistency between units of different ages is interpreted to be indicative of stress controlled magnetite recrystallization at the site. It is inferred that this recrystallization is responsible for the multicomponent remanent magnetization (RM) in these samples, which was probably acquired over long periods of time.
Flux transfer events: Scale size and interior structure
Authors: Saunders M. A. , Russell C. T. , Sckopke N.
Published: February 2008

We report the first direct investigation of the spatial properties of flux transfer events (FTEs) at the Earth's dayside magnetopause. Simultaneous magnetometer and plasma data from the ISEE 1 and 2 satellites are combined to show that magnetosheath FTEs can have a scale size of order an Earth radius in the magnetopause normal direction. We confirm that the magnetic field within the events appears to be twisted, this twisting corresponding to a core field‐aligned current of magnitude a few × 105 A. We also show evidence for plasma vorticity in FTEs. The transverse flow and field perturbations accompanying the three events studied obey approximately the Walén relation for a propagating Alfvén wave.
Can substorm expansive phase effects and low frequency Pc magnetic pulsations be attributed to the same source mechanism?
Authors: Rostoker Gordon , Samson John C.
Published: February 2008

Geomagnetic pulsations and magnetospheric substorms are often treated as separate topics in the literature. These phenomena do, however, share common properties including spatial localization and characteristic propagation velocities. In this paper we discuss the possibility that both phenomena originate from Kelvin‐Helmholtz instabilities at the interface between the low latitude boundary layer/boundary layer plasma sheet and the central plasma sheet. The variations in horizontal scale size and azimuthal velocities found in ground‐based observations of Pc 4,5, Ps 6 and westward travelling surges can be explained by variations in the shear flow and width of the regions where the instability occurs.
Crustal structure of southwestern Montana and east‐central Idaho: Results of a reversed seismic refraction line
Authors: Sheriff Steven D. , Stickney Michael C.
Published: February 2008

On October 20, 1982, we collected seismic refraction data on a 250 km line segment between Butte, Montana and Challis, Idaho. These data are from two open pit mine blasts; one at Anaconda Minerals Companys' southeast Berkely pit and the other at Cyprus Mines Corporations' Thompson creek mine. Eight of our ten recorders wrote clear records of both blasts with measured travel times accurate to +/−0.2 seconds. We supplemented these data with data from permanent stations in the Butte area. The Pg (crustal) velocity is 5.8 km/s to the southwest and 6.0 km/s to the northeast. The Pn (mantle) velocity is 7.9 km/s to the northeast and 8.1 km/s to the southwest; total travel‐times are equal. The S‐wave velocity in the crust is about 3.5 km/s. The symmetry of the travel‐time results, with their intersection within one kilometer of the midpoint between the pit blasts, strongly suggests the refraction line overlies a horizontal Moho or parallels the strike line of a dipping Moho surface. These data indicate the crust in southwestern Montana and east‐central Idaho is approximately 33 km thick. Contrasting tectonic processes, compression and thickening during the Laramide orogeny with extension and thinning since the Paleocene, resulted in a crust with slightly less than normal thickness.
Vertical distributions of particulate carbon, sulfur, and bromine in the Arctic haze and comparison with ground‐level measurements at Barrow, Alaska
Authors: Hansen A. D. A. , Rosen H.
Published: February 2008

We present results obtained during the "AGASP 1983" Arctic haze aircraft sampling experiment. We collected many filter samples and operated the LBL aethalometer, an instrument that responds to the aerosol graphitic ("black") carbon concentration in real time. We found substantial concentrations of black carbon and sulfur at all altitudes in the Arctic troposphere. Maxima in the black carbon concentrations were observed at intermediate altitudes. Comparing these results with data from the NOAA‐GMCC observatory near Barrow, Alaska, we find that peak concentrations aloft can be significantly greater than the ground‐level measurements.
Microparticle size spectrum of Arctic haze
Authors: Shaw Glenn E.
Published: February 2008

Particle size spectra of Arctic‐derived air masses were investigated during late winter and spring 1983 from Ester Dome Observatory in central Alaska. Most of the particle size distributions were bimodal with accumulation modes (geometric mean diameter 0.2µm) and nucleation modes (geometric mean diameter < 0.015µm). Virtually all mass (0.5‐5 µ g m−3) and a third to half the number of particles detected with condensation nucleus counters were in the large accumulation mode. The presence of the nucleation mode suggests that gas‐to‐particle conversion is taking place in cold, dark subpolar atmospheres at mass conversion rates of ∼ 10−21 g cm−3 s−1.
Sources of Ni, Pb, and Zn during the Arctic Episode in March 1983
Authors: Ottar Brynjulf , Pacyna Jozef M.
Published: February 2008

Atmospheric aerosols were sampled at four stations in the Norwegian Arctic and at several mainland locations in Norway during March 1983. Aerosol concentrations of Ni, Zn, and Pb were measured by atomic absorption spectrophotometry (AAS), and aerosol size fractions were analyzed by particle induced X‐ray emission (PIXE). Exceptionally high concentrations were measured in the aerosol size fractions below 2 µm diameter at the Arctic stations and at Vardo in northeastern Norway during March 7‐13, indicating an episode of long‐range transport of air pollutants into the Arctic. Trajectory analyses point to emissions from copper‐nickel smelters on the Kola Peninsula and in the Southern Urals as the main sources.
On the atmospheric transport of pollution to the Arctic
Authors: Iversen Trond
Published: February 2008

If the atmospheric processes are assumed to be nearly adiabatic, the conclusion is that the possible source areas of Arctic air pollution detected at ground level have to be situated in areas with almost the same temperature as observed in the Arctic itself. Sources south of the polar front system can only contribute to high‐altitude (or upper level) Arctic pollution. The amplitude and phase of long, planetary waves are important since they determine the position of the polar front, and provide conditions for meridional transport of air at certain longitudes.
Role of combustion‐generated carbon particles in the absorption of solar radiation in the Arctic haze
Authors: Rosen H. , Hansen A. D. A.
Published: February 2008

We have studied the vertical distributions of combustion‐generated graphitic carbon particles and their associated absorption coefficients in the Arctic. These distributions show substantial concentrations of graphitic particles throughout the Arctic troposphere. Vertical profiles in the Norwegian Arctic can show both a strongly layered structure and an almost uniform distribution. Concentrations of graphitic particles within layers can be as large as those found in typical urban areas in the United States. The absorption optical depths associated with these vertical profiles are large enough to cause a substantial change in the solar radiation balance over a highly reflecting surface.
Detection of bump‐on‐tail reduced electron velocity distributions at the electron foreshock boundary
Authors: Fitzenreiter Richard J. , Klimas Alexander J. , Scudder Jack D.
Published: February 2008

Reduced velocity distributions are derived from three‐dimensional measurements of the velocity distribution of electrons in the 7‐500 eV range in the electron foreshock. Bump‐on‐tail reduced distributions are presented for the first time at the foreshock boundary consistent with Filbert and Kellogg's proposed time‐of‐flight mechanism for generating the electron beams. In a significant number of boundary crossings, bump‐on‐tail reduced distributions were found in consecutive 3 sec measurements made 9 sec apart. We conclude that, although the beams are linearly unstable to plasma waves according to the Penrose criterion, they persist on a time scale of 3‐15 sec.
Observation of orbiting vehicle induced luminosities on the STS‐8 mission
Authors: Mende S. B. , Banks P. M. , Klingelsmith D. A.
Published: February 2008

During the STS‐8 space shuttle mission the vehicle glow was observed and photographed with an image intensified photographic camera. The altitude of the shuttle was 120 n.m.(222 km) and high intensity glow was observed, which was easily visible to the crew by naked eye. Three material test samples were mounted on the vehicle to test the dependance of the glow intensity on the nature of the surface material. These samples were exposed in the ram direction during the night side of the orbit. The glow intensity was found to depend on the nature of the surface. The mass loss suffered by the samples did not correlate with the intensity of the observed glow. The proper orientation of the shuttle with respect to the velocity vector and a camera objective grating gave a good objective spectrum of the glow in the visible region. From this it is clear that with the limited spectral resolution of the objective spectrum (about 150 A) the vehicle glow on the tail appears as continuum emission. The intensity of the tail glow becomes detectable at 4600 A and increases towards the red. Between 7000 A 8000 A a slight decrease in the glow intensity is inferred. The absolute intensity of the obliquely viewed tail glow was about 450 Rayleighs per Angstrom at around 7000 A and about 1 MR in the range within the transmission band of the image intensifier camera. The spectral distribution measured here seems to agree fairly well with that of the vehicle glow measured on the atmospheric explorer satellite.
The Earth's thermospheric superrotation from Dynamics Explorer 2
Authors: Wharton L. E. , Spencer N. W. , Mayr H. G.
Published: February 2008

Neutral thermospheric zonal winds measured from the Wind and Temperature Experiment on Dynamics Explorer 2 have been analyzed to provide a measure of the superrotation of the neutral thermosphere. The data were averaged in local time in 10 degree bands from the equator to 40 degrees latitude. The results show an average wind velocity on the order of 18 m/s to the East at the equator and a westward wind of the same magnitude at mid latitudes. Within the range of altitudes of the data base (200 to 700 km) no evidence of any significant altitude dependence was found. Averaging our data over the latitude bands studied indicates a net corotation of the thermosphere. This result is not in agreement with the superrotation value reported by King‐Hele and Walker on the basis of satellite drag analysis.
Time and temperature dependent convection models of cooling reservoirs: Application to volcanic sills
Authors: Carrigan Charles R.
Published: February 2008

A comparison between parameterized and two dimensional finite element reservoir cooling models is described. The models feature strongly temperature dependent Newtonian rheology and thermal boundary conditions simulating sills cooled from above. Cooling histories predicted by the parameterized scheme are found to be in excellent agreement with the more exact finite element calculations for viscosity variations of up to 105 occurring at a given time in the reservoir.
Surface Equatorial Current System along 23° W (July 1982‐January 1984)
Authors: Hénin Christian , Hisard Philippe
Published: February 2008

Oceanographic observations were made during the first seven cruises of the FOCAL program along 23°W from July 1982 to January 1984. Using both direct current measurements and the dynamical method the equatorial current system is described. The seasonal variations of the North Equatorial Countercurrent and South Equatorial Current are related to the wind field. A weak eastward surface current near 2°‐3°S seems to be a permanent feature during the period of observation.
New surveys of MacDonald Seamount, southcentral Pacific, following volcanoseismic activity, 1977‐1983
Authors: Talandier Jacques , Okal Emile A.
Published: February 2008

Macdonald Volcano, located at the younger end of the Austral Islands chain and discovered in 1967 from teleseismic T waves, has been the site of intense volcanoseismic swarms from 1977 to January, 1984. Three new surveys of its summit, including by scuba divers, have revealed pinnacles reaching 27 m b.s.l., and a variety of fresh features, such as fractures and spatter cones. It is strongly suggested that the summit of the volcano swelled and the pinnacles grew since Johnson’s last survey in 1975.
Fourier analysis of Nile flood levels
Authors: Hameed Sultan
Published: February 2008

Analysis of measured annual maximum and minimum levels of the river Nile for the period AD622‐1470 shows that the minima display more systematic periodicities than the maxima. These include a statistically significant signal with a period of 18.4 ± 0.4 years which is attributed to the lunar tide MN of 18.6 years which has been previously detected in precipitation records from North and South America, India and China. The analysis indicates the influence of a signal near 22 years also but the evidence for it is not unequivocal.
Carbon abundances in mantle minerals determined by nuclear reaction analysis
Authors: Mathez E. A. , Blacic J. D. , Beery J. , Maggiore C. , Hollander M.
Published: February 2008

Profiles of C concentration versus depth were determined in a spinel megacryst and two olivine crystals of a mantle xenolith from Kilbourne Hole, New Mexico, using the 12C(d,p)13C nuclear reaction technique. The 0‐1400 Å layers of all crystals are characterized by C concentrations of ∼1000 wt. ppm. This C is interpreted to be a contaminant acquired during sample preparation or ion bombardment. Below the surface, measurable C concentrations were not found in the spinel and one of the olivine crystals, but a bulk C content of 425 ppm was measured for a second crystal. The latter is interpreted to be due to the presence of discrete C‐rich phase(s) in submicroscopic inclusions or microcracks rather than C dissolved in the crystal lattice. The detection limit potentially obtainable by the (d,p) reaction technique for bulk C in minerals is several 10's of ppm.
Plasmasheet magnetic fields in the distant tail
Authors: Tsurutani B. T. , Jones D. E. , Slavin J. A. , Sibeck D. G. , Smith E. J.
Published: February 2008

Plasmasheet Bz and By have been examined for both ISEE‐3 deep tail passes. The plasmasheet Bz component has a relatively strong radial dependence, changing from a primarily northward orientation (Bz = 1.25 ± 1.57 nT, pass 2) at 60‐100 Re to an almost equal north‐south dependence (Bz = −0.20 ± 1.52 nT, pass 2; Bz = 0.22 ± 1.67 nT, pass 4) at 200‐240 Re. The large variances in the field (at all distances) are consistent with the presence of a significant amount of turbulence in the plasmasheet. The level of turbulence is relatively independent of Kp. No apparent relationship is found to exist between By and Bz. At large distances (>200 Re), Bz shows a trend to more negative values with increasing geomagnetic activity. Bz decreases by ∼ 1 nT as Kp increases from 0 to 5. Magnetic reconnection models are discussed in light of the above results.
13C/12C ratios in CO2 extracted from Antarctic ice
Authors: Friedli H. , Moor E. , Oeschger H. , Siegenthaler U. , Stauffer B.
Published: February 2008

Air is extracted from bubbles of polar ice samples by a dry extraction method, and the 13C/12C ratio is measured on CO2 separated from the air.

Ice samples of typically 700 g are crushed at ca. −20°C, the evolving air is trapped cryogenically, and CO2 is frozen out from this air for mass‐spectrometric isotope analysis. First δ13C and δ 18O results of CO2 from Antarctic ice cores are presented, and δ13C is discussed in relation to atmospheric CO2 variations. δ13C of 400 to 800 year old ice is ca. 1.1 %o higher than the 1980 atmospheric value, which agrees well with model‐based estimations. The measurement of three ca. 50,000 yr old samples yielded astonishingly low values, but contamination cannot be excluded.
36Cl as a tracer in geothermal systems: Example from Valles Caldera, New Mexico
Authors: Phillips F. M. , Goff F. , Vuataz F. , Bentley H. W. , Elmore D. , Gove H. E.
Published: February 2008

The chlorine‐36 content of three thermal waters from Valles Caldera, New Mexico has been analyzed to investigate the use of chlorine‐36 as a geothermal tracer.
Ionospheric turbulence: Interchange instabilities and chaotic fluid behavior
Authors: Huba J. D. , Hassam A. B. , Schwartz I. B. , Keskinen M. J.
Published: February 2008

We develop a set of mode coupling equations which describe the nonlinear evolution of the Rayleigh‐Taylor and
gradient drift instabilities which are relevant to the ionosphere. We show that for a three mode system, the nonlinear equations describing these instabilities correspond exactly to the Lorenz equations which approximately describe the Rayleigh‐Benard instability. It is shown that the three mode system can exhibit a strange attractor with chaotic behavior. Ion inertia plays a critical role in this phenomenon in that if it is neglected, as in the collisional limit, the three mode system does not exhibit chaos and a stable convection pattern results.
A new ozone standard: The vapor pressure of ozone at liquid argon temperatures
Authors: Mauersberger K. , Hanson D. , Morton J.
Published: February 2008

The vapor pressure of ozone has been measured at liquid argon temperatures. At the normal boiling point of argon (−185.9°C) an ozone pressure of 4.05 × 10−2 Torr was obtained with an accuracy of ±1.5%. Increases and decreases in liquid argon temperatures raised and lowered the ozone vapor pressure, respectively. During the vapor pressure measurements the purity of ozone was monitored with a mass spectrometer. The proposed ozone standard will considerably improve the calibration of experiments for atmospheric research, the determination of absorption cross sections and other laboratory ozone studies.
A mineral physics test of a pyrolite mantle
Authors: Weidner Donald J.
Published: February 2008

An homogeneous upper mantle chemical composition defined by the pyrolite model is compatible with the observed seismic velocities. Such a test is now possible for depths to 670 km as a result of new mineral elasticity and phase equilibria data. Three specific criteria for comparing the mineralogical velocity model with that of the mantle include i) the velocity jump at the 400 km discontinuity, ii) the velocity increase between 400 and 670 km, and iii) the absolute value of velocity in the 300 to 400 km region (shallower than the discontinuity). The first criterion is sensitive to the olivine content of the mantle and the pressure derivatives of the elastic properties of the high pressure phase. The application of this criterion suggests a mantle with 40 ‐ 65% olivine by volume. The second criterion is sensitive to the details of the pyroxene to garnet transformation and the relative abundances of the pyroxenes and garnet. The third criterion depends on details of this transformation as well as iron content and the temperature of the mantle.
Iron and copper enrichment of suspended particles in dispersed hydrothermal plumes along the mid‐Atlantic Ridge
Authors: Trefry John H. , Trocine Robert P. , Klinkhammer Gary P. , Rona Peter A.
Published: February 2008

Particulate Fe and Cu concentrations are used in conjunction with dissolved Mn values to identify hydrothermal venting at several sites along the Mid‐Atlantic Ridge (MAR). In dispersed hydrothermal plumes, as defined by dissolved Mn anomalies, suspended matter Fe and Cu values were as high as 15.8% and 1100 µg/g respectively, relative to Al at 1.7%. Suspended matter Fe and Cu values correlate well with dissolved Mn concentrations, tracing the intensity of dispersed plumes. In contrast with Fe and Cu, particulate Mn values in vent plumes were low at 700‐1200 µg/g. Calculated (Al + Fe + Mn)/Al ratios for MAR particles increase with increasing dissolved Mn concentrations. This ratio is used to estimate the percent hydrothermal component of the suspended matter. These sensitive tracers identify a 2‐20% hydrothermal contribution to the 10 ± 2 µg of total suspended matter/1 found along the rift valley.
Evidence for the presence of 53Mn in the early solar system
Authors: Birck Jean‐Louis , Allègre Claude J.
Published: February 2008

Chromium isotopic anomalies appear to be widespread in the Allende inclusions. Clear anomalies are shown in the 53Cr/52Cr isotopic ratio. Deviations from the terrestrial value are correlated with the Mn/Cr ratios indicating that 53Mn (half life T=3.7 × 106y) existed at the time of formation of the meteorite inclusions. The initial 53Cr/52Cr in the inclusions is lower than the terrestrial value.

Recent results have shown that chromium isotopic anomalies are frequent on the 54Cr isotope (Birck and Allègre, 1984). At the same time our results suggested the possibility of some anomalies on the 53Cr isotope which can be produced by the decay of 53Mn.

The present article presents improved precision measurements on the same inclusions of the Allende meteorite and an extension of the measurements to mineral separates. These results are the first evidence for live 53Mn in the early solar system (noted 53Mn* in the following).