bluuebunny/crossref_metadata_2025 huggingface dataset:
A new 1.3 aeon‐young achondrite
Authors: Bogard D. D. , Husain Liaquat
Published: February 2008

The 40Ar/39Ar age of Governador Valadares, a newly identified Nakhlite‐achondrite, has been determined to be 1.32 ±.04 × 109 yrs. The K‐Ar age and cosmic ray exposure age of Governador Valadares is essentially identical to analogous ages for the two other known Nakhlite‐achondrites and to Rb‐Sr ages determined for Nakhla. These data suggest that all three known meteorites of this class were derived from the same parent body by a common event, and confirm that Governador Valadares is a member of this class. The most probable heat source for producing such meteorites may be collisional melting of a portion of the parent body. Nakhlites may represent a rare phenomenon and may not be at all representative of the surface of their parent body.
Upper limit for stratospheric CLONO2 from balloon‐borne infrared measurements
Authors: Murcray D. G. , Goldman A. , Williams W. J. , Murcray F. H. , Bonomo F. S. , Bradford C. M. , Cook G. R. , Hanst P. L. , Molina M. J.
Published: February 2008

Balloon‐borne infrared sunset solar spectra in the 780 cm−1 region have been used to derive upper limits for the amount of ClONO2 in the stratosphere. These upper limits for the volume mixing ratio are 4 × 10−11 to 2 × 100−9 between 15 and 30 km with an error factor of 2. These values only show that the postulate that ClONO2 is a temporary reservoir for ClO and NO2 cannot be ruled out.
Experimental remote sensing of subsurface temperature in natural ocean water
Authors: Leonard D. A. , Caputo B. , Johnson R. L. , Hoge F. E.
Published: February 2008

A remote sensing laser Raman backscattering technique has made the first field measurements, from a boat, of subsurface temperature in natural ocean waters. These results and the measurement systems rapidly developing from them open wide areas of exploitation. The technique utilizes the observation of the 3400 cm−1 O‐H stretching Raman band of liquid water. The spectral data were analyzed to obtain the subsurface water temperature in accordance with previous laboratory studies. The importance of such a measurement by the Raman scattering technique is that it now enables depth resolved profiles of ocean water temperature to be obtained by remote sensing from airborne platforms that can be adapted for application to many problem areas of physical oceanography, meteorology, climatology, ocean technology, and thermal discharge management. An accuracy of ± 2°C has been obtained in the initial field experiments. A more refined system has been designed which will permit accuracies of better than ± 1°C in the first one or two optical attenuation lengths of depth.
Stimulated Brillouin scattering and incoherent backscatter
Authors: Fejer J. A.
Published: February 2008

Stimulated Brillouin scattering can cause asymmetries of ± 25% and ± 1% in the double humped spectra of incoherent backscatter measured at Jicamarca and at Arecibo, respectively. Errors of 10‐15 m/sec in the measured velocity could have been caused by ignoring the effects of these asymmetries at Arecibo but the typical errors were probably much smaller.
Average concentrations of OH in the troposphere, and the budgets of CH 4, CO, H 2 and CH 3CCl 3
Authors: Crutzen Paul J. , Fishman Jack
Published: February 2008

An average tropospheric OH concentration in the Northern Hemisphere of about 3 × 105 cm −3 is not in disagreement with present photokinetic information. This has important implications for the tropospheric budgets of CH 4, CO, H 2 and CH 3CCl 3. Present concentrations of CH 4 and H 2 in the atmosphere may be substantially larger than those prevailing during the pre‐industrial era, implying also an increase in H 2O concentrations and a decrease in ozone concentrations in the upper stratosphere. Accepting this estimate of an OH concentration and an important CO sink at the ground (Seiler, 1974), there must be additional sources of CO than considered in presently evaluated budgets.
Source function for tritium transport models in the Pacific
Authors: Fine Rana A. , Östlund H. Göte
Published: February 2008

An empirically fitted function describes surface Pacific Ocean tritium concentrations as varying exponentially with latitude, the r.m.s. fit to observations is 18%. The oceanic tritium concentration maximum in the North Pacific, which resulted from nuclear weapons testing, lagged the rain data by two to three years occurring in 1965‐66. Tritium‐salinity correlations are consistent with climatology. Tritium‐longitude correlations are consistent with surface water circulation.
Aftershocks of the 8 July, 1975 Canal de las Ballenas, Gulf of California, Earthquake
Authors: Munguia Luis , Reichle Michael , Reyes Alfonso , Simons Richard , Brune James
Published: February 2008

A Ms = 6.5 earthquake occurred on 8 July, 1975 in the northern part of the Gulf of California. The calculated seismic moment is 2 × 1025 dyne‐cm. This event occurred in a region of particular interest since the position of the transform fault in this region was not well known and had been locked for at least 20 years. Over 180 aftershocks were located along a zone 54 Km long, 10 Km wide and 10‐15 Km deep running between Baja California and Isla Angel de la Guarda. The depth of the aftershock zone is somewhat greater than that found in previous studies in the Gulf. The aftershock trend and that of the fault plane solution is consistent with an event occurring along a vertical strike‐slip fault with motion in the direction of known regional plate movement.
The effects of NO2 changes at twilight on tangent ray NO2 measurements
Authors: Kerr J. B. , Evans W. F. J. , McConnell J. C.
Published: February 2008

Several reported NO2 measurements are based on the inversion of absorption curves as measured from balloon platforms during sunrise or sunset. This measurement method takes advantage of the long pathlengths which result when the suns' rays pass tangentially through the atmospheric layers below the balloon. The tangent ray measurement technique may be affected by variations of NO2 concentrations at twilight since NO is being converted to NO2 during sunset and NO2 is being photolyzed to NO during sunrise. The effect of NO2 changes during twilight on tangent ray NO2 measurements has been quantitatively analyzed. The correction factors were found to be small.
On The magnetic field of Mars: Mars 2 and 3 evidence
Authors: Dolginov Sh. Sh.
Published: February 2008

Recently the existence of an intrinsic field of Mars has been questioned. In this note we review the evidence from Mars 2 and 3 from which our original conclusion of a Martian magnetic field was deduced and reaffirm our original conclusions.
The heavy metal chemistry of atmospheric rarticulate matter emitted by Mount Etna Volcano
Authors: Buat‐Ménard P. , Arnold M.
Published: February 2008

Measurements of the chemical composition of atmospheric particulate matter, collected by air filtration in the plumes from various active craters and vents at Mount Etna, Sicily, in June 1976, allowed to estimate a discharge of particulate elements to the atmosphere shown to be representative of Mount Etna long‐term activity. For some enriched trace elements in this volcanic aerosol (Cu, Zn, Se, Hg, Cd and Pb) the discharge from Mount Etna was compared to an estimate of the anthropogenic atmospheric release from the bordering countries of the Mediterranean basin. This comparison shows that, relative to the anthropogenic release of these elements, the discharge from Mount Etna is insignificant for Pb, comparable for Cd, Hg, Cu and Zn and is predominant for Se, in the Mediterranean atmospheric environment.
Wavy nature of the magnetotail neutral sheet
Authors: Lui A. T. Y. , Meng C.‐I. , Akasofu S.‐I.
Published: February 2008

Crossings of the magnetotail neutral sheet are examined with 20 s averaged magnetic field data from Imp 5 satellite. It is shown that for some multiple neutral sheet crossings, the By component reverses its sign between adjacent crossings. This feature can be explained in terms of a wavy profile of the neutral sheet along the dawn‐dusk direction, but not in terms of flapping motion or wavy profile of the neutral sheet along the tailward direction. It is suggested that the magnetotail neutral sheet often shows departure from a plane geometry.
Limits of applicability of the recrystallized grain size geopiezometer
Authors: Twiss R. J. , Sellars C. M.
Published: February 2008

Experimental work on nickel indicates the existence of a stress below which dynamic recrystallization does not occur. The limiting condition for dynamic recrystallization is that the recrystallized grain size must exceed the minimum size for the stability of a nucleus. Applying this condition to olivine indicates that the maximum possible dynamically recrystallized grain size probably exceeds the grain sizes commonly observed in mantle xenoliths.
Mantle structure beneath the Japan Sea—A re‐examination
Authors: Evans J. R. , Suyehiro K. , Sacks I. S.
Published: February 2008

We present a model for the mantle structure beneath the Japan Sea, satisfying both Rayleigh and Love wave dispersion characteristics and constraints from crustal refraction studies. The principal distinguishing feature of model JST‐14 is its lithospheric thickness of only 40 km, overlying an asthenosphere of normal oceanic velocity.
Measurement of the daytime photoelectron energy distribution from AE‐E with improved energy resolution
Authors: Lee J. S. , Doering J. P. , Bostrom C. O. , Potemra T. A.
Published: February 2008

Photoelectron energy spectra in the 150‐320 km altitude range have been obtained with the AE‐E satellite at substantial higher energy resolution than previously reported by Doering et al, Geophys. Res. Letters, 3, 129, 1976. The improvement was the result of a data analysis technique which makes use of spectra obtained from the spinning spacecraft when the potential of the sensor varies slightly with respect to the ionospheric plasma as a consequence of the v×B induced voltage in the spacecraft body. This data reduction technique has allowed the full instrumental energy resolution (ΔE/E = 2.5%) to be obtained. The results show new, weak features in the photoelectron energy spectrum and allow the determination of the line shape and area of the O and N2 304A solar radiation produced photoelectron lines as a function of altitude. The photoelectron lines are found to be essentially unbroadened by coulomb scattering below 200 km, but substantial broadening occurs by 250 km. At 300 km, the characteristic line shape due to coulomb scattering with a degradation to low energy and a sharp high energy side can be observed readily.
Solar‐polar coronal holes and the north‐south cosmic ray gradient
Authors: Agrawal S. P. , Lanzerotti L. J. , Venkatesan D.
Published: February 2008

We show, using Skylab measures of solar polar coronal hole areas, that during non‐disturbed periods the north‐south gradient of galactic cosmic rays as measured at 1 AU depends upon the difference in areas of the polar coronal holes. Higher cosmic ray fluxes are observed from the polar direction with the smaller coronal hole area.
Strontium isotopic anomalies in the Allende Meteorite
Authors: Papanastassiou D. A. , Wasserburg G. J.
Published: February 2008

We report Sr isotope anomalies in two Ca‐Al‐rich inclusions (EK1‐4‐1 and Cl) of the Allende meteorite which also contain anomalies in O, Mg, Ca, Ba, Nd and Sm. The Sr effects correspond to 84Sr or 88Sr deficits of 3.2‰ and 0.8‰ or to 86Sr excesses of 1.6‰ and 0.4‰. Although it cannot be ascertained in which isotope the anomalies reside, arguments based on the 87Sr abundance indicate that the anomalies may reside in 84Sr and 86 Sr. The data indicate deficits in the p‐process component (84Sr) up to 3.2‰ or in the r‐process component in Sr (88Sr) of up to 32‰ and are not easily reconcilable with effects in Ba and Nd, which indicate excess r, and in Sm, which indicate excess r and p components. The existence of positive and negative anomalies for many elements requires an isotopically heterogeneous solar system at the time of formation of these inclusions. The use of 87Sr/86Sr as a chronometer in the early solar system requires reevaluation, although the anomalies found in Sr thus far do not show the presence of any obvious artifacts in 87Sr/86Sr.
Auroral radar and rocket double‐probe observations of the electric field across the Harang discontinuity
Authors: Cahill L. J. , Greenwald R. A. , Nielsen E.
Published: February 2008

The region of plasma flow and electric field reversal in the late evening auroral oval was observed simultaneously by auroral radar and by rocket. A strong, 30 ‐ 50 mV/m, northward electric field was measured in the southern part of the observing region and a strong southward field in the northern part. In the middle, rocket measurements showed a weak field that rotated from north, through east, to south. In this region, no radar auroral irregularities were observed when the electric field was less than ∼ 20 mV/m.
Global circulation and distribution of hydrogen in thermosphere of Venus
Authors: Hartle R. E. , Mayr H. G. , Bauer S. J.
Published: February 2008

The global density distribution of atomic H in the upper atmosphere of Venus is determined in terms of a global circulation model. It is shown that H produced on the dayside is efficiently advected to the nightside by the major gas CO2 where it is then convected to lower altitudes and recombines. A maximum night/day H density ratio of about 5 is derived, in which case exospheric return flow from night to day strongly limits the nightside density enhancement. A previously postulated constraint connecting the eddy diffusion coefficient with the escape flux of H in one dimensional models is no longer required when global circulation of H is considered.
Parameterized mantle convection and the Earth's thermal history
Authors: Sharpe H. N. , Peltier W. R.
Published: February 2008

A simple parameterization scheme has been developed in terms of which the energetically important effects of convective heat transfer may be included in an energy balance model of the thermal history of a planet. The scheme is illustrated in the context of a discussion of the thermal history of the Earth in which mantle wide convection is assumed and the internal energy is completely primordial. The observed mean mantle viscosity from postglacial rebound strongly constrains the model.
Turbulence effects in the cyclotron resonance of monochromatic whistlers
Authors: Brinca Armando L.
Published: February 2008

The nonlinear evolution of the monochromatic whistler cyclotron resonance is responsible for a wide variety of geomagnetospheric phenomena whose interpretation has not taken into account the concomitant existence of whistler turbulence. Consideration of this whistler noise in the evolution of the coherent cyclotron resonance permits placing upper temporal bounds on the validity of the noiseless description of the interaction, and obtaining estimates for the relative intensity of the coherent mode and turbulent fields required for the onset of a typical nonlinear effect to occur. Particularization to the Siple wave injection experiment suggests that the influence of turbulence might be significant for monochromatic whistlers with weak or medium amplitudes (< 100 mγ).
Evidence for the existence of 107Pd in the early solar system
Authors: Kelly William R. , Wasserburg G. J.
Published: February 2008

The concentration and isotopic composition of Ag and Pd were measured in the Santa Clara iron meteorite. This meteorite has Pd/Ag of about 104. The isotopic composition of Pd is identical to terrestrial Pd within 0.1%. The 107Ag/109Ag ratio was 4% greater than the terrestrial value and suggests the in situ decay of 107Pd(τ½ = 6.5 × 106y) in this meteorite or its parent body. From the observed 107Ag*/110Pd ratio (* ≡ excess) we infer an initial (107Pd/110Pd)⊙ ⩾2 × 10−5. These data are incompatible with an interval of ∼ 108 y between the end of nucleosynthesis and the formation of planetary objects but are compatible with a last‐minute injection of material. The inferred existence of 107Pd and 26Al indicates that the late injection included freshly synthesized material of both intermediate and low atomic weight on a similar time scale. We estimate the fraction of freshly synthesized material to be between 10−5 to 10−4 in the region of Z ∼ 50. The 244Pu and some of the 129I present in the early solar system may be due to earlier contributions. The highly granular nature of stellar nucleosynthesis is made apparent by these considerations. The 107Pd‐107Ag chronometer is of particular importance as it can measure the time interval between the last injection of freshly synthesized material and the formation of differentiated planetary‐size objects. Our data suggest that the time scale for the differentiation of some planets into large scale metallic and silicate segregations is as short as ∼106y.
Planetary magnetic fields
Authors: Jacobs J. A.
Published: February 2008

A dimensional analysis, based on a simple model, indicates that at present both Venus and Mercury have a fluid core and an intrinsic magnetic field, but that this is not the case for Mars nor for the Moon.
Energetic neutral atom precipitation as a possible source of midlatitude F region winds
Authors: Tinsley Brian A.
Published: February 2008

Midlatitude F region winds velocities observed during main phases of magnetic storms have been shown by Hernandez and Roble to be correlated with the rate of energy input into the ring current as measured by d (Dst)/dt.

The attempt by Hernandez and Roble to relate the winds to the ring current decay mechanism of Cummings and Dessler fails because a correlation of wind velocity with positive values of d (Dst)/dt is necessary to support this mechanism rather than the observed correlation with negative values of d (Dst)/dt.

Thus an alternative mechanism for deposition of ring current associated energy into the midlatitude thermosphere is needed. The first event discussed by Hernandez and Roble shows a wind divergence at midlatitudes which is taken as evidence of direct energy input there, and there are several suitable mechanisms, some or all of which would act in addition to high latitude sources (clearly present in the absence of changes in Dst).

The mechanism of the precipitation of energetic neutral atoms arising from the charge exchange neutralization of ring current ions is suitable in all respects for a direct midlatitude energy input, except that the energy flux is several times too small, but there are reasons for the flux being greater than hitherto inferred.
Energy budget of the Volcano Stromboli, Italy
Authors: McGetchin T. R. , Chouet B. A.
Published: February 2008

Field data, including eruption movies, are used to construct a budget of the various modes of energy transport for the volcano Stromboli, Italy. At least eight distinct energy transport mechanisms can be identified. In its "normal" steady state eruption mode, Stromboli delivers approximately 1.1 Mw of power to the surface by energy transport mechanisms other than heat conduction; conducted heat probably is of the order of 6 Mw (for the part of the volcano above sea level). Convection is certainly an important mode as well and may exceed all the others, but we have no data to address the problem.

The energy budget for Stromboli, in its normal mode of activity appears to be dominated by heat conduction (and probably convection) through the surface of the ground (about 84% of the total). Heat content of the gas accounts for about 10% while the heat carried by condensed ejecta (lava fragments) and radiated heat from the vent, each contributes about 3%; the sum of all other modes is less than 1% (seismic, kinetic energy of ejecta, kinetic energy of gas, acoustic noise, heat carried in rare large flows).

Because there are at least 8 different energy transport mechanisms available and operating, we stress the importance of defining terms when comparisons are made between the energy release associated with different volcanic eruptions. The relative importance of different energy transport modes probably varies greatly both with eruption mechanism and site.
The reactions of CCl2FO2 with NO and NO2 and the thermal decomposition of CCl2FO2NO2
Authors: Simonaitis R. , Glavas Sotiris , Heicklen Julian
Published: February 2008

CCl2FO2 radicals are produced in the stratosphere from the oxidation of CCl2F radicals produced from the photodissociation of CCl3F. The reactions of CCl2FO2 with NO and NO2 have been studied by steady state photolysis at 1 atm and 286‐305°K. The reactions are with k3/k4 = 0.58 ± 0.10 over this temperature range. The thermal decomposition of CCl2FO2NO2 via the back reaction −4 was studied at 274‐305°K and 1 atm total pressure (mainly N2).

The Arrhenius expression obtained for the thermal decay is In the stratosphere CCl2FO2NO2 will be produced from reaction 4 and since its thermal lifetime at 220°K exceeds 1 year it could play a role in the stratospheric chlorine budget if it is sufficiently stable to photodissociation.
Spiral clouds on Mars: A new atmospheric phenomenon
Authors: Gierasch P. , Thomas P. , French R. , Veverka J.
Published: February 2008

Viking Orbiter images obtained during the 1978 northern summer on Mars show unusual spiral cloud patterns at high northern latitudes. Well‐developed spirals occurred only during early summer at a time when the sublimation of the annual CO2 frost cap in the north had ceased. The systems ranged in size from 200 to 500 km and all spirals were wound in a counterclockwise sense. An explanation is proposed, based on the radiatively driven instability described by Gierasch, Ingersoll, and Williams. The model predicts disturbances with the correct scale and lifetime. However, the successful development of the spirals depends on the existence of weak mean winds, suggesting that these instabilities can only develop at special null points in the general circulation. We argue that such special circumstances are most likely to occur during early northern summer and are less likely to obtain at a comparable season in the southern hemisphere.
Variations of mesospheric structures in different seasons
Authors: Czechowsky P. , Rüster R. , Schmidt G.
Published: February 2008

The SOUSY‐VHF‐Radar has been used to study the diurnal variation of the echo power received from mesospheric structures in different seasons. For the first time phase coding techniques have been applied to such measurements with a height resolution of 300 m during 6 days in summer, 5 days in autumn and 3 days in winter 1978 within the height range between 51 and 118 km. The various structures observed are classified according to characteristic features such as thickness and apparent lifetime. The results indicate the existence of four main types of mesospheric structures — blobs, sheets, thin and thick layers. Their spatial and temporal occurrence, which depends on season, is discussed.
Evidence for Earth magnetospheric tail associated phenomena at 3100 RE
Authors: Intriligator D. S. , Collard H. R. , Mihalov J. D. , Vaisberg O. L. , Wolfe J. H.
Published: February 2008

Examination of Pioneer 7 NASA Ames Research Center plasma analyzer data obtained in February 1977 at ∼3100 RE, downstream from the earth in the vicinity of the expected extended geomagnetic tail indicate that tail related phenomena may have been observed. These observations are characterized by intermittent intervals of extremely low levels of plasma ion flux. Corresponding Prognoz 5 Space Research Institute plasma ion data obtained in the vicinity of earth indicate typical solar wind flux levels and a relatively steady character to the solar wind during this time. These recent Pioneer 7 observations in the vicinity of the expected geomagnetic tail at ∼3100 RE are consistent with our earlier Pioneer 7 observations in September 1966 at ∼1000 RE and our Pioneer 8 observations in January 1968 at ∼500 E and represent the most extended positive observational information of the extended nature of the geomagnetic tail. These measurements suggest that at times Jupiter's magnetosphere may have tail associated phenomena extending to distances of ∼10 AU downstream from the planet. These measurements also raise the possibility that at times comets may have tail associated phenomena extending downstream from the visible tail.
Nitric oxide measurements in the equatorial Pacific region
Authors: McFarland M. , Kley D. , Drummond J. W. , Schmeltekopf A. L. , Winkler R. H.
Published: February 2008

Surface nitric oxide mixing ratios were measured in the equatorial Pacific region using a chemiluminescent detector. The average NO mixing ratio was about 4 pptv during noontime conditions for nine days of measurements. These NO mixing ratios, which are much lower than any previously reported, imply that the O3 production rate due to CO and CH4 oxidation may be less than previously believed. They also imply smaller OH/HO ratios as a consequence of the lower HO2 to OH² conversion by NO.
Fault‐plane solutions for microearthquakes preceding the Thanksgiving Day, 1974, Earthquake at Hollister, California
Authors: Warren David H.
Published: February 2008

Fault‐plane solutions were obtained for 80 microearthquakes in a 900‐km² area centered on the Busch fault during a 1‐year period preceding the Thanksgiving Day, 1974, Hollister, Calif., earthquake. Strike‐slip motion occurred in 64 of these quakes, mainly at active points on the Sargent, Castro, Busch, and Calaveras faults. Eleven of the solutions are thrust type, and five are normal. No large rotation (greater than 45°) of the compressional axes was observed before the earthquake, but changes of about 20° or less would be possible.
Pitch‐angle diffusion by whistler mode waves near the Io plasma torus
Authors: Scarf F. L. , Coroniti F. V. , Gurnett D. A. , Kurth W. S.
Published: February 2008

As Voyager 1 traversed the inner radiation belt of Jupiter, wave‐particle interactions involving energetic electrons and whistler mode turbulence were strongly affected by the presence of the Io plasma torus. Within the high density torus the resonant electron energy was low and the associated high index of refraction yielded high B‐to‐E ratios for the wave fields, leading to very strong pitch‐angle scattering. We show that significant spatial and temporal variations in plasma conditions produced large fluctuations in local scattering times, and we discuss the problems associated with the evaluation of precipitation lifetimes.
Rapid subauroral ion drifts observed by Atmosphere Explorer C
Authors: Spiro R. W. , Heelis R. A. , Hanson W. B.
Published: February 2008

Large subauroral convection velocities are striking features of the vector ion drift measurements made with the RPA's and drift meters on the Atmosphere Explorer satellites. The large AE‐C data base has been utilized to investigate the character and morphology of this phenomenon. These latitudinally narrow features are found to be confined predominantly to the local time sector between 18:00 hrs and 02:00 hrs. They occur either singly or as multiple events, one of which nearly always straddles the equatorward edge of the auroral zone. Their occurrence probability as a function of AE index suggests a dependence on magnetic substorm activity.
A search in a marine sediment core for 10Be concentration variations during a geomagnetic field reversal
Authors: Raisbeck G. M. , Yiou F. , Fruneau M. , Loiseaux J. M. , Lieuvin M. , Ravel J. C. , Hays J. D.
Published: February 2008

A search has been made for variations in the 10Be concentration in a North Pacific marine sediment core during the period of a geomagnetic reversal. The 10Be was counted directly using an accelerator techniquethus permitting an order of magnitude improvement in time resolution compared to earlier 10Be measurements. No significant 10Be variations were seenand several possible reasons are discussed. The measured 10Be deposition rate is substantially larger than in any previously studied sediment.
Venus tectonics: Another Earth or another Mars?
Authors: McGill George E.
Published: February 2008

The presence of presumably primordial large craters has led to the suggestion that Venus may have a thick lithosphere like that of Mars despite its similarities to Earth in size and density. Howevercrust and upper mantle temperatures on Venus are very likely higher than on Earth so that a dry Venus could have a lithosphere with a thickness similar to that of Earth. If a trace of volatiles is present in the mantlethe lithosphere of Venus could be thinner. Due to the absence of liquid watererosion and deposition will be much slower on Venus than on Earthfavoring retention of primordial cratered surfaces on portions of the crust that have not been destroyed or buried by tectonic and volcanic activity. Geochemical models of solar system origin and petrological considerations suggest that K is about as abundant in Venus as in Earth. The abundance of 40Ar in the atmosphere of Venus lies somewhere between the Earth value and one‐tenth of the Earth value. Because erosional liberation of 40Ar on Venus will be relatively inefficientthis range for 40Ar abundance at least permits an active tectonic historyand if the 40Ar abundance is towards the high end of the rangeit may well require an active tectonic history. Thus we are not constrained to a Mars‐like model of Venus tectonics by craters and possible mantle dryness; an Earth‐like model is equally probable.
Structure and properties of Jupiter’s magnetoplasmadisc
Authors: Barbosa D. D. , Gurnett D. A. , Kurth W. S. , Scarf F. L.
Published: February 2008

Voyager 1 plasma wave observations have revealed the existence of an Earth‐like continuum radiation trapped in Jupiter’s magnetospheric cavity at frequencies below the solar wind plasma frequency. This radiation serves as an accurate diagnostic of the local electron number density throughout most of Jupiter’s outer magnetosphere and yields information regarding the gross configuration of the magnetoplasmadisc as well as its kinematical properties. Using magnetic field observationswe are able to construct radial profiles of plasma pressuredensityand temperature from 20‐80 RJ in the early morning plasma sheet along with plasma sheet crossings and estimated thicknesses. The study suggests that hot protons (∽ 10 keV) are the dominant constituents of the plasma sheet (⋍ 4.2 RJ average thickness) out to 80 RJ beyond which centrifugal effects take over and distort the sheet towards the rotational equator.
Chemistry of meteor metals in the stratosphere
Authors: Murad Edmond , Swider William
Published: February 2008

NaOH, which has recently been suggested as a precursor for ionic species in the stratosphere may be destroyed by reactions with chlorinated species such as Cl, ClO and HCl. Besides sodium, compounds of other metals, e.g. Si, Mg, Fe, and A1 may also react with various chlorinated species. A few of these reactions are discussed.
Apatite saturation in basic to intermediate magmas
Authors: Watson E. Bruce
Published: February 2008

The solubility of fluorapatite in magmatic liquids ranging in composition from olivine melilitite to andesite was determined by fusion of powdered rock samples in fluorapatite capsules and subsequent analysis of the quenched glasses with an electron microprobe. Over the temperature range 1165° ‐ 1275°C at 1 atmosphere pressure, saturation of the melts in apatite is controlled by three primary variables: 1) concentration of P2O5, 2) concentration of SiO2, and 3) temperature. As SiO2 concentration increases from 30 to 55 wt% at 1250°C, the amount of dissolved P2O5 required to saturate a melt in apatite decreases from 12 to less than 4 wt%. At 1165°, the saturation level is uniformly ∼ 36% lower than at 1250°C. By comparison of these results with P2O5 concentrations in natural basalts, it is clear that few basic lavas are saturated in apatite at the time of extrusion. Extrapolation of the data to high‐pressure conditions in the upper mantle is tenuous at the present time, but the low‐pressure data suggest that any apatite present in regions of basalt production may be consumed during melting.
A model of the SO2 atmosphere and ionosphere of Io
Authors: Kumar S.
Published: February 2008

The calculations of thermal structure for an SO2 atmosphere of Io lead to exospheric temperatures in 800‐1200K range. The Pioneer 10 electron density profiles can be fit with an SO2 surface density of 1.2 × 1011 cm−3 at 5:30 pm local time and exosphere temperature of 1030°K. Low energy electrons provide the major ionization source but the solar UV absorption dominates the heating of the atmosphere due to the long wavelength absorption threshold of SO2 and large absorption cross‐sections.
Radial diffusion in Io's torus: Some implications from Voyager I
Authors: Froidevaux Lucien
Published: February 2008

Data from several Voyager 1 experiments are used to determine the magnitude and L dependence of the radial diffusion coefficient for low‐energy charged particles outside of Io's orbit under steady‐state conditions. The extreme ultraviolet observations near 685Å are inverted to produce an ion density profile for L > 6. This normalized ion profile, as well as the (equatorial) electron density profile estimated from the planetary radio astronomy (PRA) observations falls off as L−5. Such a density gradient would make possible centrifugally driven cross‐L diffusion outside of Io's orbit without ruling out the presence of an atmospherically driven mechanism. A lower limit for the radial diffusion coefficient DLL is 1.5 × 10−10 L5 RJ² sec−1, yielding a characteristic diffusion time from 6RJ to 7RJ of less than 10 days, much shorter than previously anticipated. Steady‐state diffusion is not a good assumption inside of Io's orbit, where the particle densities decrease sharply from 6RJ to 5RJ; the diffusion time in that region is probably longer than outside of Io's orbit.
Time dependent plasma injection by Io
Authors: Richardson John D. , Siscoe George L. , Bagenal F. , Sullivan James D.
Published: February 2008

A two parameter model of time‐dependent, flux‐tube interchange diffusion is fit to the Voyager 1 plasma data obtained in the Io plasma disk. The interpretation of the parameters required to achieve the fit is that plasma injection increased suddenly and substantially (by more than an order of magnitude) at some time prior to the arrival of Voyager 1 (between 1 and 100 days prior). The injection rate was about 2 × 1029±1 ion/sec. At this rate, the centrifugally driven interchange instability dominated outward diffusion, causing the outward diffusion rate to be about a factor of 50 greater than the inward diffusion rate. The material diffusing inward had time to cool by radiation, possibly accounting for the observed temperature drop inside the orbit of Io.
Study of electric fields parallel to the magnetic lines of force using artificially injected energetic electrons
Authors: Wilhelm K. , Bernstein W. , Whalen B. A.
Published: February 2008

Electron beam experiments using rocket‐borne instrumentation will be discussed. The observations indicate that reflections of energetic electrons may occur at possible electric field configurations parallel to the direction of the magnetic lines of force in an altitude range of several thousand kilometers above the ionosphere.
On the cause of plasma‐sheet thinning during magnetospheric substorms
Authors: Hill T. W. , Reiff P. H.
Published: February 2008

We propose that the thinning of the plasma sheet during magnetospheric substorms is caused by an earthward gradient of the rate of magnetic merging (field annihilation) in the tail current sheet, which is in turn caused by the velocity‐dependent access of plasma mantle particles to the current sheet. A simple model calculation based on this effect predicts a thinning time constant of the order of 1 hour, consistent with observations. The mechanism is also consistent with the observed correlation between plasma‐sheet thinning and southward‐directed magnetic field components in the solar wind.
Isotopically anomalous silver in the Santa Clara and Piñon iron meteorites
Authors: Kaiser T. , Kelly W. R. , Wasserburg G. J.
Published: February 2008

The isotopic composition and concentration of Ag and the concentration of Pd have been determined in the Santa Clara and Piñon iron meteorites. It is shown that these meteorites contain isotopically anomalous Ag with an excess of 107Ag relative to normal Ag, confirming earlier findings. Using an improved procedure for cleaning the sample surface from terrestrial Ag, a new concentration of 1‐4×1011 atoms of 109Ag/g meteorite is established which is an order of magnitude below the levels found earlier. As a result ratios of 107Ag/109Ag were found which are enriched in 107Ag by 60% to 160%. The existence of an excess 107Ag in these two meteorites, which have high 108Pd/109Ag ratios of ∼ 7×104, is established. These findings are consistent with the in situ decay of extinct 107Pd (τ½ = 6.5×106y) produced by a late nucleosynthetic event shortly before solar system formation; however, production of Ag isotopes by reaction of cosmic ray secondaries with the Pd isotopes in the meteorites cannot be excluded.
Tsunami height and earthquake magnitude: Theoretical basis of an empirical relation
Authors: Comer Robert P.
Published: February 2008

The relation between maximum far‐field tsunami amplitude H and earthquake magnitude Mw has recently been investigated empirically by Abe (1979) who noted that for large circum‐Pacific earthquakes Mw ≃ log H + B, where B depends on the source location and on the region of tsunami observations. We have predicted theoretically the scaling of far‐field tsunami amplitudes with seismic moment and fault area, by combining relations between seismic parameters (assuming constant stress drop) by estimating scaling relations between fault area, average slip, and tsunami source dimensions, and by using some results from basic hydrodynamics. The theoretical predictions imply relations of the form Mw = (4/3) log H + B′ if dispersion during the propagation of the tsunami waves is neglected, and Mw = (2/3) log H + B″ in the highly dispersive limit, which closely match and bracket the empirical relation.
Atmospheric drag as the cause of the secular decrease in the semimajor axis of Lageos's orbit
Authors: Rubincam David Parry
Published: February 2008

An unmodeled acceleration is causing the semimajor axis of Lageos to decrease at the rate of about 1.1 mm day−1. Drag from charged particles or neutral helium or both is the most probable cause. The rate of orbital decay is conceivably explained by the theories of charged particle drag. Unfortunately, these theories are not yet developed to the point where a definitive statement as to the importance of charged particle drag can be made. Neutral helium may also be the cause of the orbital decay. While the abundance required to account for the secular decrease is high, it also helps solve the "helium problem." Neutral hydrogen probably accounts for no more than 12 percent of the observed decay.
On the compensation mechanism of the Walvis Ridge
Authors: Angevine C. L. , Turcotte D. L.
Published: February 2008

The Walvis Ridge in the south Atlantic Ocean is correlated with the geoid anomalies obtained from the GEOS 3 satellite. It is shown that the correlation is best explained by Pratt compensation with a depth of compensation of twenty to thirty kilometers.
Density and temperature profiles obtained by lidar between 35 and 70 km
Authors: Hauchecorne Alain , Chanin Marie‐Lise
Published: February 2008

A lidar system based at the Haute‐Provence Observatory (44°N, 6°E) has been used to obtain night‐time density and temperature profiles in the altitude range 35‐70 km. If the lidar results are normalized to an in‐situ rocket sounding from 35 to 40 km, the lidar and rocket profiles are in quite good agreement up to about 50 km. Differences are sometimes noted around 55 km, and these could possibly be caused by an aerosol layer.
Lower mantle phase transitions may generally have negative pressure‐temperature slopes
Authors: Navrotsky Alexandra
Published: February 2008

Phase transitions in oxides at pressures above about 150 kbar may commonly have negative pressure‐temperature slopes. The causes of the higher entropies of denser phases include low frequency vibrations of small atoms in sites having high coordination number and long metal‐oxygen distances, decrease in directional bonding, positional disorder and possible solid‐electrolyte behavior, and semiconductor‐metal and metal‐metal transitions.
Initial geomagnetic field model from Magsat vector data
Authors: Langel R. A. , Estes R. H. , Mead G. D. , Fabiano E. B. , Lancaster E. R.
Published: February 2008

Magsat data from the magnetically quiet days of November 5‐6, 1979, were used to derive a thirteenth degree and order spherical harmonic geomagnetic field model, MGST(6/80). The model utilized both scalar and high‐accuracy vector data and fit that data with root‐mean‐square deviations of 8.2, 6.9, 7.6 and 7.4 nT for the scalar magnitude, Br, Bθ, and Bø, respectively. The model includes the three first‐order coefficients of the external field. Comparison with averaged Dst indicates that zero Dst corresponds with 25 nT of horizontal field from external sources. When compared with earlier models, the earth's dipole moment continues to decrease at a rate of about 26 nT/yr. Evaluation of earlier models with Magsat data shows that the scalar field at the Magsat epoch is best predicted by the POGO(2/72) model but that the WC80, AWC/75 and IGS/75 are better for predicting vector fields.
Ground based spectroscopic measurements of HCl
Authors: Marché Pierre , Barbe Alain , Secroun Claude , Corr John , Jouve Pierre
Published: February 2008

The vertical profile and total column concentration of HCl have been measured from ground based high resolution infrared absorption spectra. The lines recorded were the R1 and P5 of HCl35 at 2942.731 cm−1 and 2775.760 cm−1 respectively. Vertical profiles and column concentrations are reported for different seasons. Measurements indicate an HCl volume mixing ratio equal to (2.2 ± 0.5) × 10−11 at 10 km increasing to (3.4 ± 0.6) × 10−9 at 33 km.
Some necessary conditions for a critical velocity interaction between the ionospheric plasma and a xenon cloud
Authors: Axnäs I.
Published: February 2008

The conditions for an experiment to study the critical ionization velocity effect in the interaction between a Xenon cloud, released from a satellite, and the ionospheric plasma are investigated. The model used is based on the assumption that there exists an effective process that transfers the energy, that is available in the relative motion, to the electrons. Some necessary conditions to obtain significant heating or deceleration of the plasma penetrating the cloud are calculated. The conditions are mainly given by the energy available in the relative motion and the rates of the different binary collision processes involved. As the released gas cloud expands the possibilities for a critical velocity interaction will exist only within a certain range of cloud radii. It is shown that the charge transfer collision cross section between the ionospheric ions and the cloud atoms is an important parameter and that Xenon is a very suitable gas in that respect.
Mount St. Helens, Washington, 1980 volcanic eruption: Characterization of organic compounds in ash samples
Authors: Pereira W. E. , Rostad C. E. , Taylor H. E.
Published: February 2008

Volcanic ash samples obtained after the May 18, eruption of Mount St. Helens, Washington, were analyzed for organic compounds. Several n‐alkanes, fatty acids, dicarboxylic acids, alcohols, phenols, aldehydes, aromatic acids, aromatic and polycyclic aromatic hydrocarbons and chlorinated aromatic compounds were identified by GC‐MS. Pyrolysis of plants and soil organic matter is the most probable source of these compounds.
Tidal dissipation in Europa: A correction
Authors: Cassen P. , Peale S. J. , Reynolds R. T.
Published: February 2008

The possibility that tidal dissipation in a thin ice crust was sufficient to preserve liquid water on Jupiter's satellite Europa was suggested by Cassen et al. [1979]. However, their calculation of the tidal heating rate for that situation is in error. For the same parameter values, the actual heating rate would be much less than that given in the cited paper. Thus, their conclusion regarding the possibility that liquid water exists today on Europa is considerably weakened. The purposes of this paper are to correct the calculation of the tidal dissipation rate in a Europan ice crust, to discuss briefly the implications for Europa's thermal history, and to clarify certain aspects of the tidal heating problem which should have been obvious to the authors of the original paper.
Magma chamber and mantle reflections – East Pacific Rise
Authors: Herron Thomas J. , Stoffa Paul L. , Buhl Peter
Published: February 2008

A multichannel seismic reflection profile of stacked and migrated common depth point data across the East Pacific Rise near the Siqueiros Fracture Zone supports and extends previous observations (at two crossings 27 to 50 km to the south) of reflections assumed to be from the top of a magma chamber and of reflections from the M‐discontinuity. The reflection assumed to be associated with the top of the magma chamber is 1‐1/2 to 2 km below the sea floor. The combined results of the three crossings suggest that the chamber is continuous along the Rise crest and that its width, which varies from 2 to 8 km, correlates with the width of the Rise crest as indicated by the bathymetric contours. The reflections from the crust‐mantle boundary can be detected beneath the raised axial block of the East Pacific Rise and although weak, can be detected beneath the magma chamber.
Identification of auroral EUV emissions
Authors: Fischer F. , Stasek G. , Schmidtke G.
Published: February 2008

From measurements of two rocket flights and from laboratory investigations auroral EUV emissions are identified. Contrary to the airglow, emissions from ionized nitrogen are present in the auroral emission spectra below 80 nm.
Sam II aerosol profile measurements, Poker Flat, Alaska; July 16‐19, 1979
Authors: McCormick M. Patrick , Chu William P. , McMaster Leonard R. , Grams Gerald W. , Herman Benjamin M. , Pepin Theodore J. , Russell Philip B. , Swissler Thomas J.
Published: February 2008

SAM II satellite measurements during the July 1979 Poker Flat mission, yielded an aerosol extinction coefficient of 10−4 km−1 at 1.0 µm wavelength, in the region of the stratospheric aerosol mixing ratio peak (12‐16 km). The stratospheric aerosol optical depth for these data, calculated from the tropopause through 30 km, is approximately 0.001. These results are consistent with the average 1979 summertime values found throughout the Arctic.
Measurements of the absorption coefficient of stratospheric aerosols
Authors: Ogren J. A. , Ahlquist N. C. , Clarke A. D. , Charlson R. J.
Published: February 2008

A method for determining the visible absorption coefficient of stratospheric aerosols is presented. The first eight samples had a median value of 4 × 10−9m−1, with an uncertainty of about ± 5 × 10−9m−1. The resulting estimated single‐scattering albedo was in the range 0.96‐1.0.
Radiative properties of the background stratospheric aerosols and implications for perturbed conditions
Authors: Pollack James B. , Toon Owen B. , Wiedman Donald
Published: February 2008

We have carried out a series of Mie scattering calculations to define the wavelength‐dependent, single scattering properties of aerosols present in the stratosphere during July 1979. Additional radiative transfer computations were conducted to assess the impact of aerosols on Earth’s radiation budget. For these purposes, we employed an extensive set of measurements of aerosol characteristics that were obtained in Alaska from aircraft and satellite platforms. At that time, the optical depth was too small for aerosols to significantly impact Earth’s climate. But the optical depth of the stratospheric aerosol layer has been large enough during some volcanically perturbed periods for the aerosols to have caused a noticeable warming of the stratosphere and cooling of the troposphere.