bluuebunny/crossref_metadata_2025 huggingface dataset:
Meteoric material and the behavior of upper stratospheric polar ozone
Authors: Aikin A. C. , McPeters R. D.
Published: February 2008

Analysis of October SBUV ozone profile data in the antarctic polar vortex shows that there was a decrease in ozone between 1979 and 1984 of between 15 and 30% at all levels from 30 mb to 0.7 mb. During spring of 1983 at 75° to 80°S the ozone mixing ratio at 1 mb decreases continuously from September through the summer solstice and then increases in late summer and fall, but we observe much less ozone at 1 mb in September and October than under similar conditions in the fall. This asymmetry between spring and fall ozone values may be the direct result of the sudden release of chlorine bound by meteoric material during polar night. Meteoric atoms, X, descending from the mesosphere react with the atmosphere to produce XOH, which will interact with HCl to form salts, XCl. Since these processes continue in the absence of sunlight, chlorine may accumulate during polar winter. The sudden release of this chlorine from photodissociation of these salts during spring could give rise to the loss of ozone in the upper stratosphere. At 30 mb ozone decreases substantially in mid‐September and remains at a low value until the mid‐October increase. Different mechanisms may be required to explain the ozone decreases in the upper stratosphere and in the lower stratosphere.
Large ozone losses in Antarctica: The role of heating perturbations
Authors: Pyle J. A.
Published: February 2008

Using a two‐dimensional circulation model the possible influence on the polar ozone column of modifications to lower stratospheric heating rates, both within the polar vortex and in middle latitudes, has been examined. Using reasonable heating rates it is not possible to change the model ozone to reproduce observed ozone losses in Antarctica. If an additional model heating is introduced at, or just before, the end of the southern hemisphere polar night, the time scales are such that appreciable ozone changes do not occur for at least three months.
Free oscillations and surface waves of an aspherical Earth
Authors: Mochizuki E.
Published: February 2008

The correspondence between free oscillations and surface waves of a laterally heterogeneous earth is established. Starting from the Born approximation of Woodhouse, for large angular order, coupling between neighbouring multiplets along the same dispersion branch leads to the apparent distance shift noted by Woodhouse and Dziewonski, which they obtained from a surface wave approach.
Global relationship between oceanic geoid and seafloor depth: New results
Authors: Cazenave Anny , Dominh Kien
Published: February 2008

A new global transfer function (admittance) between oceanic geoid and seafloor depth has been derived for the wavelength band 1000‐4000 km, after removal of lithospheric cooling effects using the most recently published crustal ages of the oceans. In this wavelength band, the admittance is positive, reaches a maximum of ∼ 5m/km around 2750 km wavelength, then decreases to ∼ 2.5 m/km, on the average, at shorter wavelengths (between 2500 km and 1000 km). These values are systematically higher by 30‐40% than those we derived in a previous study using crustal ages of poorer quality.

In view of these new results, we cannot exclude that part of the signal at the 2750 km wavelength is of convective origin, unlike the conclusions of the previous study. On the other hand, at shorter wavelengths, the observed admittance can still be interpreted in terms of crustal thickening and sediment loading.
Time‐dependent convection in elongated Rayleigh‐Benard cells
Authors: Christensen Ulrich R.
Published: February 2008

The onset of time‐dependence and some subsequent transitions in two‐dimensional Rayleigh‐Bénard cells of aspect ratios a=2.5 and a=4 are studied numerically for a Boussinesq fluid of infinite Prandtl number. Oscillatory convection starts at a Rayleigh number of only 21,000 (a=2.5) or 12,000 (a=4.0) for stress‐free boundaries. Above Ra=100,000 the cells with a=4.0 break down into several short cells, whereas single cells with a=2.5 remain stable to at least Ra=500,000. With rigid boundaries the tendency towards break‐up into short cells is found to be more pronounced. Long‐wavelength cells, modulated by travelling boundary‐layer instabilities, appear to be a likely form of convection in the earth's mantle.
Regional trends in radiogenic heat generation in the Precambrian basement of the Western Canadian Basin
Authors: Jones F. W. , Majorowicz J. A.
Published: February 2008

Radiogenic heat generation values for 381 basement samples from 229 sites in the western Canadian basin exhibit a lognormal frequency distribution. The mean value  = 2.06 (S.D. = 1.22) µWm−3 is larger than the radiogenic heat generation values reported for the shield in the Superior (ca. 1.2 µWm−3, Jessop and Lewis, 1978) and Churchill (ca. 0.7 µWm−3, Drury, 1985) provinces. When equal Log A contour intervals are used to map the basement heat generation, three large zones of relatively high heat generation are found. One coincides with the Peace River Arch basement structure and one with the Athabasca axis (Darnley, 1981). There is no apparent indication of increased heat flow through the Paleozoic formations associated with these two zones. The third zone, in southwestern Saskatchewan, coincides with a high heat flow zone in the Swift Current area. The lack of correlation between heat flow and heat generation in Alberta may be due to the disturbance to the heat flow in the Paleozoic formations by water motion, or may indicate that the heat is from uranium, thorium and potassium isotope enrichment near the basement surface rather than enrichment throughout the entire upper crust.
Multiple‐event relocation of earthquakes near the Gorda Rise ‐ Mendocino Fracture Zone intersection
Authors: Sverdrup Keith A.
Published: February 2008

Earthquakes along the southern edge of the Gorda plate and the Mendocino fracture zone that were relocated jointly generally tend to move 25 to 35 km southwest of their PDE and ISC locations. This has the effect of reducing the number of events occurring deep in the plate and increasing the number of events located on the Gorda rise as well as revealing a tightly grouped linear zone of activity extending along the Mendocino fracture zone. The resulting spatial pattern of seismicity is more consistent with recent models of the tectonics of the Gorda plate and the Mendocino fracture zone.
The Viking Project
Authors: Hultqvist Bengt
Published: February 2008

The Viking project is presented and put into a wider scientific perspective. The spacecraft, its orbit and the payload are briefly discussed and related to earlier projects. Some new operational characteristics are described, including the real time data analysis during "campaigns" at Kiruna, the close cooperation between experimenters and satellite operators, the quick delivery of experimenters' data tapes and the fast distribution of quick‐look plots (QLPs). Finally a short list of physics highlights from the early analysis of Viking data is presented.
The development of the substorm expansive phase: The “eye” of the substorm
Authors: Rostoker Gordon , Jones A. Vallance , Gattinger R. L. , Anger C. D. , Murphree J. S.
Published: February 2008

The explosive onset and development of a clearly defined auroral substorm has been analysed using data from the ultraviolet imager aboard the VIKING satellite. These data permit the evolution of the substorm to be traced with a time resolution as high as 40 seconds. The envelope of the disturbed region ‐ the "eye" ‐ expands both poleward and azimuthally to the east and west reaching an azimuthal extent of almost six hours of magnetic local time after about 15 minutes. The poleward expansion involves irregular poleward motion accompanying intensifications within the eye, with the maximum poleward displacement being at the meridian of the center of the eye. Within the "eye", discrete regions of enhanced luminosity develop with a tendency for each newly disturbed region to be to the west of the previous ones. It is, however, observed that a newly excited region can be to the east of the pre‐existing activated region. Each new intensification is accompanied by a brief further poleward expansion of the high latitude edge of the "eye". Each region of enhanced luminosity within the "eye" remains relatively stationary and fluctuates in intensity over its lifetime. We identify these regions of enhanced luminosity with westward traveling surges as defined from ground observations in the earlier literature. Our UV imager data demonstrate that these surges do not necessarily propagate although the overall envelope of the substorm disturbed region expands both eastward and westward during the lifetime of the event.
Geomagnetic field‐line resonant harmonics measured by the Viking and Ampte/CCE magnetic field experiments
Authors: Zanetti L. J. , Potemra T. A. , Erlandson R. E. , Engebretson M. J. , Acuña M. H.
Published: February 2008

We report the first simultaneous observations of multiple harmonic, azimuthally polarized, ULF pulsations at two points along a geomagnetic flux tube in space. In March 1986, the elliptically orbiting equatorial AMPTE/CCE satellite was oriented with the apogee near 0830 hours magnetic local time (MLT), and the orbital plane of the polarorbiting Viking satellite was at 1000 MLT. The satellites were situated within approximately the same flux tube but with an effective separation of approximately 10 Re near L = 8 on the inbound pass of the AMPTE/CCE orbit. Structured harmonic pulsations were observed by the magnetic field experiments on both spacecraft, and they appeared to turn off and on simultaneously at both locations. Both the observations and the relative amplitudes along the magnetic field lines support recent ideas of multiple field‐line resonances of Alfvén waves.
A new method to derive “instantaneous” high‐latitude potential distributions from satellite measurements including auroral imager data
Authors: Marklund G. T. , Blomberg L. G. , Potemra T. A. , Murphree J. S. , Rich F. J. , Stasiewicz K.
Published: February 2008

Electric field, magnetic field, auroral imager and particle observations obtained on the Viking satellite for one dusk‐dawn crossing through the polar cusp, are used to illustrate a new promising technique to derive “instantaneous” pictures of the high‐latitude electrodynamics. Global electric field distributions are calculated using as input UV‐imager data of the auroral distribution and in situ measurements of the electrodynamical parameters along the Viking orbit, which are combined with measured average distributions of field‐aligned currents (Region 1 and 2) and conductivities representing the diffuse auroral background. The input data (j∥ and ΣP, ΣH) with contributions from both the diffuse auroral background and active regions, and the output data (E) are tested and calibrated to the Viking measurements by point‐by‐point quantitative comparisons along the magnetic footpoint of the satellite. The calculations are done iteratively to refine and improve both the input and the output. The results demonstrate that selfconsistent and realistic solutions of the prevailing “instantaneous” auroral electrodynamics are possible to obtain in this manner.
Auroral hiss and kilometric radiation measured from the Viking satellite
Authors: Bahnsen Axel , Jespersen Mogens , Ungstrup Eigil , Iversen Iver B.
Published: February 2008

An extensive data base on high latitude waves will result from the ten month's operating period of the Viking satellite, during which the high frequency wave experiment, V4H, has worked continuously. Preliminary analysis of a small fraction of these data has given results concerning auroral kilometric radiation (AKR) as well as lower frequency waves. Our findings are: (1) AKR waves exist in both R‐X and L‐O mode, R‐X mode being strongest, (2) the frequency range of AKR is from about 100 kHz to at least 500 kHz, (3) the R‐X mode propagates upwards in a cone or conical shell filling less than a half sphere, (4) AKR is generated in a narrow latitudinal range within the auroral oval, in the evening sector, and at altitudes of several thousand kilometers, (5) AKR is electromagnetic at the source, no strong electrostatic mode is observed, (6) there is fine structure in AKR, as well as a continuous spectrum, (7) below the cyclotron frequency, auroral hiss, limited upwards by the plasma frequency, as well as Z mode radiation has been observed, (8) in the polar cap, electrostatic bursts of a few seconds duration are frequently observed.
Two‐dimensional structure of the solar wind near the Sun
Authors: Washimi Haruichi , Yoshino Yutaka , Ogino Tatsuki
Published: February 2008

The two‐dimensional structure of the solar wind near the sun is analyzed by the method of MHD simulation. The helmet‐streamer configuration with a sharp boundary between the closed and open field regions has been reproduced. Due to the pressure‐driven current in the sheet, the magnetic field, which has a dipole configuration at the photosphere, is found to behave like R−2 at a large distance, R, from the sun.
The effect of the hot oxygen corona on the interaction of the solar wind with Venus
Authors: Belotserkovskii O. M. , Breus T. K. , Krymskii A. M. , Ya Mitnitskii V. , Nagy A. F. , Gombosi T. I.
Published: February 2008

A numerical gas dynamic model, which includes the effects of mass loading of the shocked solar wind, was used to calculate the density and magnetic field variations in the magnetosheath of Venus. These calculations were carried out for conditions corresponding to a specific orbit of the Pioneer Venus Orbiter (PVO orbit 582). A comparison of the model predictions and the measured shock position, density and magnetic field values showed a reasonable agreement, indicating that a gas dynamic model that includes the effects of mass loading can be used to predict these parameters.
Stratospheric lidar profiles from Mauna Loa Observatory, winter 1985‐1986
Authors: DeFoor Tom , Robinson Elmer
Published: February 2008

In the period from mid‐November 1985 through April 1986 the stratospheric aerosol profiles determined by lidar observations at the Mauna Loa, Hawaii Observatory indicated a persistent sequence of profiles characteristic of stratospheric volcanic aerosols. Aerosol layers were observed in two general altitude ranges. A high layer between about 25 and 27 km was detected in late November 1985 and again in late February and late March 1986. A lower layer, generally located between 20 and 23 km was present from early December 1985 through April 1986. These layers appear to have been due to the November 13, 1985 eruption of Nevado del Ruiz in Columbia. On the basis of these lidar data the impact of this volcanic plume on direct solar irradiance at 694 nm in Hawaii was estimated to have been an average diminution of about 0.4 per cent during the period December 1985 through April 1986.
Can neutral particles from comet Halley have reached the ice spacecraft?
Authors: Daly P. W.
Published: February 2008

To investigate the question of how neutral particles could travel from comet Halley to the ICE spacecraft, Kepler orbits are calculated that connect the positions of Halley and ICE, in space and time. From these orbits, the initial speed of the particle, relative to Halley, can be found as a function of departure time. It is found that there is a minimum relative speed of 7.5 km s−1, for particles leaving the comet on February 6, 1986, three days before perihelion. Particles emitted before this date actually require a higher relative speed. Lower speeds of about 5 km s−1 are again possible for departure dates in November, 1985, when the molecular production rate is considerably reduced.
Image restoration using the point spread function of the Halley Multicolour Camera
Authors: Kramm J. R. , Möhring W. , Keller H. U.
Published: February 2008

The optical resolution of the Halley Multicolour Camera (HMC) is limited by its finite aperture, by minute mechanical degradations within the instrument, and by the high speed time delay and integration (TDI) illumination method adapted to the spin of the spacecraft. The sum of all implies a visible loss of image sharpness. The smearing effect has been calibrated using images of a star which can be considered as a point source. The images were superimposed in the frequency domain with subpixel accuracy. With these means the point spread function (PSF) has been determined and applied to the received images using Fourier methods. The effectiveness of the scheme is demonstrated on images of the earth and comet Halley.
Lidar observations of the mesospheric sodium layer at Syowa Station, Antarctica
Authors: Nomura A. , Kano T. , Iwasaka Y. , Fukunishi H. , Hirasawa T. , Kawaguchi S.
Published: February 2008

The mesospheric sodium layer was measured for 42 nights during the period from April to October, 1985, at Syowa Station (69°00′ S, 39°35′ E), Antarctica, by using a dye laser radar (lidar) tuned to the D2 line of sodium. This observation was made as part of the Middle Atmosphere Program (MAP). In contrast to the results obtained at mid‐latitudes in the northern hemisphere, the seasonal variation in abundance showed no significant winter maximum. Further, there was no apparent seasonal variation in the vertical distribution of sodium density. However, we observed oscillatory variations in abundance with a period of about 40 days. The nocturnal variations in the sodium density profile have a wavelike structure with a vertical wavelength of 10 to 16 km and a period of 3 to 8 hours, which suggests strongly that gravity waves are propagating upward through the sodium layer. The sodium lidar measurements during auroral activity give evidence that the layer is disturbed associated with the auroral breakup event.
Small cumuli observed with a 3 mm wavelength Doppler radar
Authors: Lhermitte Roger M.
Published: February 2008

The paper presents quantitative millimeter wave Doppler radar observations of radar reflectivity and air vertical velocity inside shallow cumuli whose vertical development is restricted by a capping inversion layer. The maximum observed radar reflectivity is −34 to −30 dBZ, which is equivalent to a cloud liquid water content of 0.1 to 0.25 g/m³ depending on cloud droplet size. The main updraft region, which coincides roughly with the maximum reflectivity region, occupies the center of the cloud and extends throughout the radar‐visible cloud depth. Downdrafts exhibit more complex structure and are found on the cloud edges.
Vorticity measurement in a region of coastal ocean eddies by observation of near‐inertial oscillations
Authors: Duda Timothy F. , Cox Charles S.
Published: February 2008

Continuously repeated hourly profiles of horizontal velocity have been collected with the Cartesian diver profiler on each side of a front. The location was roughly 100 km west of Point Buchon, California, in a region of the California current dominated by offshore coastal jets and strong eddies. Concurrent temperature records from the quasi‐Lagrangian diver indicate that one set of 21 profiles was taken on the southerly side of the front with cold surface water, while an immediately following set of 16 was collected on the other side. For the 3 day collection period, average advection of the diver was .2 m/s to the WNW. The horizontal kinetic energy levels of the profiles are the same for either side of the front, and are 4.2 J/m³, roughly twice the Garrett‐Munk model level, but these also include subinertial baroclinic velocities. Cross spectral analysis of the repeated profiles is used to determine the dominant intrinsic rotation frequencies of horizontal velocity for vertical wavenumbers between .00625 and .019 cpm. In the absence of local vorticity, this would be expected to be the local inertial frequency f. On the cold (southerly) side of the front, most rotation frequencies were above f, while most were below f on the warm side. The mean frequencies were 1.18f and 0.78f. The difference between these dominant intrinsic frequencies and f can be attributed to local relative vorticity. These vorticity estimates are consistent with the westward advection of the diver being due to positions first south of then north of the central region of an offshore jet.
Static magnetic field models consistent with nearly isotropic plasma pressure
Authors: Spence Harlan E. , Kivelson Margaret G. , Walker Raymond J.
Published: February 2008

Using the empirical magnetospheric magnetic field models of Tsyganenko and Usmanov (TU), we have determined the self‐consistent plasma pressure gradients and anisotropies along the midnight meridian in the near‐Earth magnetosphere. By “inverting” the magnetic field, we determine what distributions of an anisotropic plasma, confined within the specified magnetic field configuration, are consistent with the magnetohydrostatic equilibrium condition, J × B = ∇ · P. The TU model, parameterized for different levels of geomagnetic activity by the Kp index, provided the magnetic field values from which J × B was numerically evaluated. A best fit solution was found that minimized the average difference between J × B and ∇ · P along an entire flux tube. Unlike previous semi‐empirical models, the TU models contain magnetic stresses that can be balanced by a nearly isotropic plasma pressure with a reasonable radial gradient at the equator.
Seasonal air and water mass redistribution effects on LAGEOS and Starlette
Authors: Gutierrez Roberto , Wilson Clark R.
Published: February 2008

We computed zonal geopotential coefficients from average seasonal variations in global air and water mass distribution. These coefficients are used to predict the seasonal variations of LAGEOS' and Starlette's orbital node, δΩ, and the seasonal δJ3 for Starlette. A comparison of these predictions with the observed values indicates that air pressure and, to a lesser extent, water storage may be responsible for a large portion of the currently unmodeled variation in the earth's gravity field.
Measurements of OH(X²π) in the stratosphere by high resolution UV spectroscopy
Authors: Torr D. G. , Torr M. R. , Swift W. , Fennelly J. , Liu G.
Published: February 2008

The hydroxyl radical, OH, is one of the key constituents which moderates the removal of stratospheric ozone. Measurements of OH have proved difficult to acquire and as a result the empirical database on OH in the stratosphere is extremely sparse. In this paper we report the first results obtained using high spectral resolution imaging ultraviolet spectroscopy to observe multiple rotational lines of OH A²Σ−X²π (0‐0) band. A 9.2 Å spectral segment from 3075.8 Å to 3085.0 Å is imaged at 0.08 Å FWHM spectral resolution allowing the simultaneous acquisition of six of the brightest OH resonance fluorescence emission lines. The high spectral resolution and low scattered light design of the instrument allows these lines to be detected above the Rayleigh scattered sunlight background. The technique permits remote sensing of stratospheric OH from a high altitude instrument. The instrument was flown to an altitude of 40 km on August 25, 1983, and again on June 12, 1986, on scientific balloons from Palestine, Texas. The OH profiles inverted from the limb scans made during these flights are reported here. These profiles represent the first measurements of the temporal variation of OH over an extended height range. The results demonstrate that the technique can be used to monitor OH from orbit.
An examination of possible solar wind sources for a sudden brightening of comet IRAS‐Araki‐Alcock
Authors: Russell C. T. , Luhmann J. G. , Baker D. N.
Published: February 2008

Possible solar wind sources for a sudden global brightening of Comet IRAS‐Araki‐Alcock are examined. No increases in solar wind momentum flux, solar energetic particles or solar activity occurred coincident with these brightenings. The only change in the solar wind coincident with the brightenings was a rotation of the interplanetary magnetic field to a more flow‐aligned state. If this rotation did not lead to the cometary brightening, the brightening must have been intrinsic to the comet.
Orientation of olivine in dunite from elastic wave velocity measurements
Authors: Sayers Colin M.
Published: February 2008

There is a strong correlation between the measured elastic anisotropy of dunite and the preferred orientation of its main component, olivine. Olivine is a major constituent of the mantle and dunite is considered representative of upper mantle materials. In this report the measured elastic wave velocities for a dunite from Hidaka Horoman are used to determine the coefficients W1mn of a series expansion of the crystallite orientation distribution function in generalised Legendre functions. This function gives the probability of a crystallite having a given orientation with respect to a set of axes fixed in the rock. The solution to this problem allows construction of crystallographic pole figures, which indicate a strong alignment of olivine a‐axes in agreement with the conclusions of petrofabric examination. Seismic studies of the crystallite orientation distribution function are therefore feasible and these should lead to a better understanding of the deformation processes associated with flow in the upper mantle.
Evolutionary structures in double‐diffusive convection in magma chambers
Authors: Hansen Ulrich , Yuen David A.
Published: February 2008

Finite‐amplitude solutions to subcritical, time‐dependent, double‐diffusive convection (D.D.C.) applicable for magma chambers are obtained by a two‐dimensional, finite‐element method based on stream‐function, temperature and compositional fields. Grid‐refinement is used for resolving the disparately‐scaled thermal and chemical boundary layers present for large ratios of the thermal to chemical diffusivity (Lewis number) characteristic of magmas. The occurrence of layered convection depends strongly on the initial conditions of the temperature and composition. It is shown that in the infinite Prandtl number limit a local transition from a diffusive to a finger‐like regime can take place for large enough Lewis numbers. This time‐dependent finding suggests that a strict categorization of D.D.C. into the finger and diffusive regimes requires modification in geological applications.
Sterling revisited: The seismic source for a cavity‐decoupled explosion
Authors: Glenn L. A. , Denny M. D. , Rial J. A.
Published: February 2008

In the STERLING event, a 0.38 kt nuclear device was exploded inside a roughly spherical cavity, of approximately 17 m radius. The cavity, located in the Tatum salt dome (near Hattiesburg, Mississippi), had been created by a 5.3 kt tamped explosion more than 2 years earlier (SALMON event). Analysis of data obtained in SALMON and STERLING indicated a corner frequency for STERLING near 10 Hz, a factor of 4 less than predicted by the simplest decoupling theory. We have performed a comprehensive re‐examination of the experimental records and find that the original report was incorrect, a consequence of not properly accounting for noise in the seismic analysis. The new study, based on direct spectral analysis of the free‐field data, indicates that the STERLING experiment was in near perfect agreement with theory. This is a potentially significant result for seismic monitoring of a low‐yield threshold test ban.
Hydrogen peroxide in air during winter over the south‐central United States
Authors: Van Valin C. C. , Ray J. D. , Boatman J. F. , Gunter R. L.
Published: February 2008

Hydrogen peroxide and other atmospheric trace gases were measured along the 91°30′ meridian from near the Iowa border to the Gulf of Mexico during February 1987. The measured H2O2 values were within the range of <0.1 to 1.0 ppbv and an increase in concentration from north to south of 0.04‐0.05 ppbv per degree of latitude was observed on five of six flights. The concentration of H2O2 appeared to be primarily dependent upon air mass history; concentration discontinuities were observed when the aircraft flew across air mass boundaries. H2O2 measurements during flights in air masses of similar histories during daylight and night showed no significant difference in concentration. Neither was there a consistent dependence of the H2O2 concentration upon altitude.
40Ar/39Ar laser dating of single grains: Ages of Quaternary tephra from the East Eifel Volcanic Field, FRG
Authors: v. d. Bogaard Paul , Hall Chris M. , Schmincke Hans‐Ulrich , York Derek
Published: February 2008

Four late Pleistocene tephra deposits from the East Eifel volcanic field have been dated by 40Ar/39Ar single grain laser fusion of K‐feldspar and phlogopite crystals. This is a high‐speed and high precision technique which, because it is grain‐specific, can directly detect the presence of older contaminating material. Our results indicate that the Hüttenberg tephra from Wehr volcano erupted 213±4 ka BP, and that the Rieden volcanic complex erupted at least over the period 410 to 470 ka BP. Essential Rieden phonolite lapilli contain abundant sanidine with apparent ages older than the eruption age.
Viscous relaxation of a compressible spherical shell
Authors: Li Guoying , Yuen David A.
Published: February 2008

We develop analytical solutions for analyzing viscous relaxation of a compressible mantle to surface loading. Two different models are considered: one in which the density step of the core‐mantle boundary (CMB) is held fixed and the other in which the mass of the Earth remains invariant with respect to variations of equation of state parameters. For thermodynamic parameters characteristic of the mantle, relaxation times of the fundamental and first overtone modes change by no more than about 30% for degree less than 4. For a given initial depression, the ratio between the velocity in the lower mantle and that at the surface is bigger for incompressible models than for compressible models. Eigenfunctions between the two models also differ in appearance throughout the mantle, with the incompressible ones being larger for the second model. These results would suggest that the resolution of mantle viscosity may be impaired by the smaller excitation in the lower mantle due to effects of mantle compressibility.
Stratospheric trace gas detection using a new balloon‐borne ACIMS method: Acetonitrile, acetone, and nitric acid
Authors: Knop G. , Arnold F.
Published: February 2008

The first test flight of a new balloon‐borne ACIMS (Active Chemical Ionisation Mass Spectrometry) instrument developed at our laboratory was successful and provided a wealth of new and interesting information on stratospheric trace gases. In the present paper, a brief discussion of the experimental method is given and trace gas abundances of acetonitrile (CH3CN), acetone ((CH3)2CO), and nitric acid (HNO3) are presented.
Zonal winds between 25 and 120 km obtained from solar occultation spectra
Authors: van Cleef Garrett W. , Shaw John H. , Farmer Crofton B.
Published: February 2008

Zonal winds between altitudes of 25 and 120 km have been obtained from measurements of the Doppler shifts of lines of atmospheric gases in solar occultation spectra collected with the ATMOS spectrometer flown on Spacelab 3. Wind speeds of about 100 ms−1 near 100 km and 25 to 50 ms−1 between 25 and 70 km were observed at latitudes near 30°N and 50°S. The wind speeds were estimated to ± 5 ms−1 and positions of the absorption lines relative to the rest frame of the instrument were simultaneously recovered to 5 × 10−5cm−1.
Suggested explanation of heavy ozone
Authors: Bates David R.
Published: February 2008

The formation of ozone by the termolecular association of atomic and molecular oxygen is discussed. On taking the relevant symmetry numbers into account it is inferred that there is an enhancement that depends on τ(R)/τ(D) where τ(R) is the energy randomization time and τ(D) is the lifetime of the activated complex. To explain the observed enhancement τ(R)/τ(D) would have to be about a third which is within the rather wide range that the uncertainties in τ(R) and τ(D) allow.
Gaseous mercury profiles in the tropical Pacific Ocean
Authors: Kim Jonathan , Fitzgerald William
Published: February 2008

The distribution of dissolved gaseous mercury (DGM) was determined at four hydrographic stations in the tropical Pacific Ocean. These vertical profiles of DGM, to a depth of 400 meters, are the first obtained for the open ocean. Dissolved gaseous Hg concentrations generally increased with depth. The major portion of DGM in surface sea water was of an inorganic gaseous form, probably elemental Hg (Hgo). In two instances, organic gaseous Hg, presumably dimethyl Hg [(CH3)2Hg], was observed in the deeper waters. These results suggest that bacteria may be responsible for producing Hgo and (CH3)2Hg at depth in this ocean region.
A comparison between short‐period and long‐period Q models
Authors: Clements John Robert , Abdul‐Rahman Kamarudin
Published: February 2008

In this study, the power spectra of short‐period P waves were obtained from a network of 17 stations in order to measure P‐wave attenuation in the entire mantle. A Q‐depth relationship was estimated from the use of a Southern Alaskan earthquake and a Novaya Zemlya nuclear explosion. For the determination of t* values from stations, the power spectra were obtained using the instantaneous maximum likelihood method for frequencies of 0.5, 1.0 and 1.5 Hz. Attempts to obtain a satisfactory Q model by inversion of the differential travel times and t* values were unsuccessful. An indirect approach was therefore used to obtain the Q‐depth relationship. The resulting Q model was then compared with existing long‐period Q models. This short‐period Q model shows a high‐Q zone near the middle of the mantle. These short‐period Q values were higher than those Q values at longer periods.
Three step double layers in the laboratory
Authors: Bailey Andrew , Hershkowitz Noah
Published: February 2008

A new class of stationary double layer structure, with three or more distinct steps, is demonstrated in the laboratory. A large monotonic potential increase results from a series of smaller double layers (each with eΔϕ/Te ∼ 1–3). In many respects, these double layer structures resemble those inferred from satellite measurements of auroral double layers. This new class of double layer appears to depend on turbulence for its existence and to be a hybrid structure, intermediate between anomalous resistivity and BGK double layers.
Distribution of major stratospheric warmings in relation to the quasi‐biennial oscillation
Authors: Dunkerton Timothy J. , Delisi Donald P. , Baldwin Mark P.
Published: February 2008

Data from 1953 to the present indicate that major warmings in the northern hemisphere winter have not occurred when the equatorial monthly mean zonal winds are deep westerly, i.e., westerly over more than about 5/8 of the 10–85 mb layer. Sixteen winters have had a major warming in the last 35 years. Six January–February periods had deep equatorial westerlies but did not experience a major warming.

Major warmings do not require deep equatorial easterlies, nor is the occurrence of a major warming significantly correlated with the sign of the zonal mean wind at any particular level between 10 and 50 mb, although as noted by previous investigators, more than half of the observed major warmings have occurred when the equatorial flow is easterly at a given level between 10 and 50 mb. We suggest that a more relevant QBO statistic may be found in the depth of QBO wind regimes.

The previously proposed connection between the equatorial quasi‐biennial oscillation and the major warmings of the northern hemisphere winter is supported by these observations.
A mechanism for patchy reconnection at the dayside magnetopause
Authors: La Belle‐Hamer A. L. , Fu Z. F. , Lee L. C.
Published: February 2008

In this paper, the Kelvin‐Helmholtz (KH) and tearing instabilities at the dayside magnetopause are examined. It is found from simulations that the development of the KH instability modulates the current sheet, creating separated pinched regions. The growth rate of the tearing instability is enhanced in these pinched regions and diminished in the regions separating them. Based on these findings, we propose that a possible mechanism for patchy reconnection at the dayside magnetopause is the development of the KH instability.
Electrostatic electron cyclotron harmonic (ESCH) echoes found near the plasmapause by the EXOS‐B (Jikiken) satellite
Authors: Ono Takayuki , Oya Hiroshi
Published: February 2008

A stimulated plasma wave experiment by the EXOS‐B satellite showed the appearance of echoes of plasma waves with a delay time of several msec. We examined the frequency dependence of the echoes in comparison with the observed plasma resonances and the dispersion relation of plasma waves. The propagation mode of the echoes was identified as the electrostatic electron cyclotron harmonic (ESCH) waves. The appearance regions were examined with respect to the electron density profiles in the magnetosphere that have been determined by measuring the frequencies of stimulated plasma resonances. The ESCH echoes are frequently observed in a detached plasma region. Near the plasmapause the appearance of echoes is significantly frequent in regions where the plasma density is rapidly increasing in the plasmasphere due to a strong supply from the ionsphere. Because of their propagation mode and the state of the plasma density profiles in their appearance regions in the magnetosphere, the echoes are inferred to be produced by the reflection of propagating ESCH waves from small‐scale density irregularities of environmental plasma.
A new component of terrestrial radio emission observed from ISEE‐3 and ISEE‐1 in the solar wind
Authors: Steinberg J.‐L , Lacombe C. , Hoang S.
Published: February 2008

At a time when the AE index was 1300, the radio receivers on board ISEE‐3 (216 RE sunward of Earth) and ISEE‐1 recorded a new type of terrestrial radio emission between 20 and 50 kHz. The radiation had a smooth time profile, with a negative frequency drift; its angular diameter at 47 kHz was at least 170°. This smooth component followed the onset of a TKR burst whose angular diameter was 50° at the same frequency 47 kHz and varied as f−2, i.e., was controlled by interplanetary scattering. Because of its time association with the TKR burst, the source of the smooth radiation must have been in the Earth environment. We suggest that it was produced or leaked into the interplanetary medium very far from Earth in order that the scattering path to ISEE‐3 be long enough (2000 RE) to account for the observed angular diameter. More than 50 such events, clearly distinct from the Earth non thermal continuum, were observed between 1978 and 1983.
Interplanetary protons (Ep ≈ 1 MeV) 1973‐1986 and Out to 22.4 AU
Authors: Van Allen J. A. , Decker R. B.
Published: February 2008

This paper uses annual mean counting rate data from detectors on two long‐lived spacecraft, Pioneer 11 and IMP 8, to study the temporal and heliocentric radial distance variations of the intensity of interplanetary protons (Ep ≈ 1 MeV) over solar activity cycle 21. The Pioneer 11 data cover the time period April 1973 through 1986 and the heliocentric radial distance range 1.0 < r < 22.4 AU. IMP 8, in an approximately circular geocentric orbit of semimajor axis 35 earth radii, provides comparable data at 1 AU over the time period 1974‐1986. The combination of the two bodies of data shows that the annual mean intensity of such protons varies as the inverse square of the distance from the sun, i.e., as r−α with α = 2.0 (±0.2), irrespective of solar activity as measured by the annual mean sunspot number S. Also it is found (a) that the annual mean intensity at 1 AU is approximately proportional to S, except for anomalously low values in 1979 and 1980 and (b) that the product of the annual mean intensity at Pioneer 11 by r² is also approximately proportional to S, except for anomalously low values in 1979, 1980 (in particular), and 1981. The common “1980 anomaly” is attributed to gross changes in interplanetary conditions associated with the reversal of the polarity of the sun's polar magnetic field.
On the net transfer of carbon dioxide from liquid precipitation to the atmosphere
Authors: Sequeira R.
Published: February 2008

Most of the water‐soluble carbonate and non‐marine calcium (Ca*) in background aerosol in the northern hemisphere could originate as calcium carbonate (CaCO3) of arid soil origin. This is most relevant to the tropics, and a good portion of the temperate latitude belt. However, at equilibrium pH‐values between about 6 and 7, the dissolved carbonate is primarily present as the bicarbonate (HCO3−). Selecting a random set of precipitation samples in the same pH‐range, the HCO3−/Ca* stoichiometric ratio values were evaluated for a number of background locations in the northern hemisphere. The representative range observed is ∼ 0.04‐0.5. Assuming that acid‐base neutralization reactions are ubiquitous, the above range of ratio values suggests that aqueous precipitation at the surface ‐ or possibly some raindrops aloft ‐ in background locations affected by arid aerosol could act as a net source of carbon dioxide (CO2) to the atmosphere, and not vice versa, as has been universally assumed or implied in the past.
Ammonia emissions from biomass burning
Authors: Hegg Dean A. , Radke Lawrence F. , Hobbs Peter V. , Riggan Philip J.
Published: February 2008

Measurements in the plumes from seven forest fires show that the concentrations of NH3 were considerably in excess of ambient values. Calculation of NH3 emissions from the fires, based on the ratio of NH3/CO in the plumes and emissions of CO from biomass burning, suggest that biomass burning may be a significant source of atmospheric NH3.
Evidence for anisotropy in north east Africa, from geographical and azimuthal distribution of Rayleigh wave velocities, and average upper mantle structure
Authors: Hadiouche Ouiza , Jobert Nelly
Published: February 2008

Long period surface waves from WWSSN, GDSN, SRO and GEOSCOPE stations are analysed to obtain the dispersion of surface waves in the North‐East of Africa. Lateral variations of Rayleigh wave velocities are retrieved simultaneously with the average azimuthal anisotropy. As a first result, the low velocity anomaly under the Red Sea is apparent at all periods. A second result is a nearly North‐South direction of maximum group and phase velocities. This azimuthal anisotropy direction is in agreement with the direction of absolute plate motion in this region.

Anisotropy is also evidenced by simultaneous inversion of Love and Rayleigh wave dispersion along the path TAM‐AGD. In the resulting models, isotropic and anisotropic, very low mantle SV‐wave velocities extend up to the Moho. For SH waves, we find a strong discrepancy with SV waves, SH‐wave velocities being higher by 5% down to 200 km under the crust. This is characteristic of lithospheric polarization anisotropy.

The S‐wave anisotropy (polarization and azimuthal) found in this region, including the Red Sea, is compatible with the absolute motion of the African plate: it can be interpreted, considering the low lithospheric S‐velocities, as a consequence of plastic flow in the weak lithosphere of an anomalous mantle. This anisotropy, evidenced here on S waves, may be due, as Pn and lithospheric S‐wave anisotropy found in other continental areas, to dynamical processes related to plate motion.
Fractal interpretation of the linear relation between logarithms of maximum amplitude and hypocentral distance
Authors: Sato Haruo
Published: February 2008

The linear relation between logarithms of maximum amplitude and hypocentral distance are known to hold good observationally. But, the direct evaluation of the Q−1 factor from the linear coefficient has been difficult. Here, supposing a random and fractally homogeneous distribution of absorbers or scatterers with fractal dimension Da in a space of dimension d, we can analytically calculate the relation between amplitude and distance. The commonly accepted exponential decay formula corresponds to a special case of Da=d. The amplitude is written as a negative power of distance in the case of Da=d‐1: the negative power is directly related to the linear coefficient between logarithms of amplitude and distance. If seismic faults correspond to absorbers or scatterers, the equality Da=d‐1 is qualitatively in harmony with the well known fact that the hypocenter distribution of microearthquakes has a fractal dimension being smaller than d.
Isothermal plateau fission‐track age of the Late Pleistocene Old Crow Tephra, Alaska
Authors: Westgate John
Published: February 2008

Hydrated glass shards of the widespread Old Crow tephra in Alaska have been dated by the isothermal plateau fission‐track method, which corrects for partial track fading, if present. The weighted mean age of 149±13 ka is older than previous estimates, which range from 86 to 109 ka. These new data support the view that Old Crow tephra was deposited during the cold interval that immediately preceded the last interglacial, which is dated in the marine record at 125 ka B.P. It is likely, therefore, that the buried forest beds and numerous ice‐wedge pseudomorphs, preserved in sediments just above Old Crow tephra in interior Alaska, relate to the last interglacial and not a younger warm event of early Wisconsin age.
Constraints and interpretation of 87Sr/86Sr ratios in Cenozoic dolomites
Authors: Vahrenkamp Volker C. , Swart Peter K. , Ruiz Joaquin
Published: February 2008

Replacement dolomitization by seawater has been modeled in order to quantify the Sr‐isotope signature in Cenozoic dolomites as a function of precursor mineralogy and 87Sr/86Sr ratio, reaction stoichiometry and 87Sr/86Sr ratio of the dolomitizing fluids. High Sr carbonates, such as aragonite, may introduce a significant precursor memory into an otherwise seawater dominated Sr‐isotope signature if small quantities of seawater per unit volume of precursor carbonate are involved. Dolomitization of low Sr carbonates (i.e. low‐Mg calcite) are shown to create an isotopic signature indistinguishable from that of the seawater involved in the reaction. Therefore, by comparison with the Sr‐isotope evolution curve of seawater, the‐ 87Sr/86Sr ratios of the dolomites can be used to record the oldest possible age of dolomitization and the youngest age of deposition.

The implications for this approach have been applied to data obtained from a dolomitized core from Little Bahama Bank, Bahamas. Two periods of dolomitization are recognized, one in the early Late Miocene involving Middle Miocene or older rocks, and a second one around 2.4 Ma ago affecting early Pliocene carbonates.
The three‐dimensional morphology of the Antarctic Ozone Minimum
Authors: Aikin A. C. , McPeters R. D.
Published: February 2008

The three‐dimensional morphology of the spring Antarctic ozone distribution as determined by the Nimbus 7 SBUV instrument is presented for the period October 1–11, 1986. The data show that a clearly defined minimum in ozone relative to the local ozone field extends throughout the stratosphere from the tropopause to above 50 km, though decreasing in intensity with altitude. Near 18 km, ozone in the ozone hole is 50% less than the average surrounding ozone. But even at 50 km the ozone is 20% less than the surrounding ozone field. The ozone minimum in the upper stratosphere is displaced about 6 degrees toward the equator so that observations at a fixed station may provide the illusion that the ozone minimum is restricted only to low altitudes. While the ozone minimum is spatially coherent throughout the stratosphere, there are differences in the behavior of ozone at different altitudes that suggest the existence of at least three distinct altitude domains. Below 30 km, ozone is characterized by classic “ozone hole” behavior. Between 33 and 43 km ozone is more stable, actually increasing during September and October. Above 43 km, ozone has always decreased during September to a minimum in October, but it has also suffered a long‐term decrease of 7–12% since 1979.