bluuebunny/crossref_metadata_2025 huggingface dataset:
Snowfall induced by a power plant plume
Authors: Parungo Farn P. , Allee Paul A. , Weickmann Helmut K.
Published: February 2008

Fly ash released from a coal‐fired power plant was detected as active ice nuclei. Observational evidence is presented that the plume aerosol inadvertently seeded supercooled fog and induced local snowfall. Snow crystals were replicated and examined with an electron microscope. Individual ice nuclei were analyzed with an X‐ray energy spectrometer. Most ice nuclei contained Si, Al, S, Ca, and Fe which are major components of fly ash. It is interesting to note that plume aerosol can seed clouds at temperatures as warm as −5°C and produce needle‐shaped snow crystals.
Interhemispheric gradients of CF2Cl2, CFCl3, CCl4, and N2O
Authors: Tyson Bennett J. , Arvesen John C. , O'Hara Dean
Published: February 2008

Direct, real‐time gas chromatographic measurements of CF2Cl2, CFCl3, CCl4, and N2O were made at latitudes from 74°N to 62°S aboard a NASA Convair 990 as part of the 1976 NASA CV‐990 Latitude Survey Mission between Alaska and New Zealand. A difference was found in the average mixing ratios of CF2Cl2 and CFCl3 between the northern and southern hemispheres, but no differences were noted for CCl4 and N2O. The results support some of the previous studies of interhemispheric tropospheric gradients and suggest the lack of any significant tropospheric sinks.
Solar wind interaction with the Moon: Enhanced magnetic field fluctuations at low altitudes
Authors: Weiss H. , Russell C. T. , Lichtenstein B. R. , Coleman P. J.
Published: February 2008

Evidence of a magnetically turbulent region above the lunar dayside is presented. This region apparently exists when the moon is in the solar wind and is approximately 100 kms thick. Possible explanations for the presence of a dayside turbulent sheath are investigated and, to within the accuracy of the data, none can satisfactorily explain its presence.
Objections to the N2+ + e− dissociative recombination coefficients inferred from analysis of Atmosphere Explorer measurements
Authors: Biondi Manfred A.
Published: February 2008

It is shown that Orsini, et al's inference, from an analysis of Atmosphere Explorer data, that N2+ ions in vibrationally excited states exhibit dissociative recombination coefficients in excess of 10−6 cm³/sec is incorrect. From the theory of the dissociative recombination process, an upper limit of ∼ 10−7 cm³/sec is obtained for recombination by N2+ ions in a particular vibration state at F‐region electron temperatures. Available laboratory data on dissociative recombination of simple ions support this conclusion. As a possible alternative for the apparent rapid loss of vibrationally excited ions in the F‐region it is suggested that the reaction N2+ + O → N + NO+ may exhibit the necessary increase in reaction rate with vibrational excitation in the ions.
Modeling continental crust: Structural and chemical constraints
Authors: Smithson Scott B.
Published: February 2008

Seismic reflection studies reveal lateral and vertical heterogeneity of the deep crust that is comparable to that indicated by geologic observations. In a crust this heterogeneous, the concept of a “Conrad Discontinuity” has little meaning. Near‐horizontal reflectors in the deep crust are formed by horizontal movements in metamorphic rocks and magmatic crystallization within the earth’s gravity field. Supracrustal rocks in the lower crust suggest that much of the crust was built up as a supracrustal pile. Mean crustal composition is approximately quartz dioritic to granodioritic. This composition cannot be achieved by simply adding material through accretion of andesitic island arcs but must account for more felsic material.
Preliminary measurements of the ion component of the incoherent scatter spectrum in the 60‐90 km region over Arecibo
Authors: Harper Robert M.
Published: February 2008

Preliminary measurements of the ion component of the incoherent scatter spectrum are presented. The observations show qualitative agreement with theory if the effects of negative ions and experimental sources of spectral broadening are considered. The measurements indicate that neutral winds can be measured down to about 65 km during the daytime at Arecibo. Accuracies of 2.5 m/sec for the horizontal components, and 0.6 m/sec in the vertical component can be obtained below 80 km after one‐half hour integration.
Possible variations in atmospheric ozone related to the eleven‐year solar cycle
Authors: Penner Joyce E. , Chang Julius S.
Published: February 2008

Changes in ozone, temperature, and other minor constituents resulting from eleven‐year variations in the solar flux between 180 and 340 nm are presented. Results were computed using a one‐dimensional time dependent model that allows for all major feedbacks and time delays which may result from changing photolysis rates in the Ox‐ NOx‐ HOx‐ CℓOxsystem.

Since the 1950's the chlorine content of the stratosphere has been increasing. The effect of this increase on ozone variability during the last two solar cycles is analyzed. Expected variations in O3and temperature resulting from changes in the uv flux are compared to available measurements.
Interpretation of an ATS 6 Alfvén wave using solutions with finite ionospheric conductivity
Authors: Allan W. , Knox F. B.
Published: February 2008

A recently reported standing Alfvén wave at ATS 6 is reinterpreted using axisymmetric toroidal‐mode solutions which involve realistic ionospheric height‐integrated conductivities. Details of possible wave‐forms are deduced, and it is suggested that the wave may be interpreted as either a modified form of the classical half‐wave resonance, or as an example of the recently predicted quarter‐wave resonance.
Imaging radar observations of Askja Caldera, Iceland
Authors: Malin Michael C. , Evans Diane , Elachi Charles
Published: February 2008

Surface roughness of nine radar backscatter units in the Askja Caldera region of Iceland was examined in computer‐enhanced like‐ and cross‐polarized radar images. A field survey of the caldera was then used to check the accuracy of the preliminary analysis. There was good agreement between predicted surface roughness of backscatter units and surface roughness observed in the field. In some cases, variations could be correlated with previously mapped geologic units.
First measurements of mesospheric vertical velocities by VHF radar at temperate latitudes
Authors: Miller K. L. , Bowhill S. A. , Gibbs K. P. , Countryman I. D.
Published: February 2008

A program of ground‐based VHF measurements of turbulence and of wave and tidal motions in the mesosphere has been initiated by the University of Illinois using a high‐power radar facility located at Urbana, Illinois. Observations show scattering occurring intermittently during the daytime throughout the mesosphere. Vertical velocities exhibit the presence of gravity waves with dominant periods near 10 min and amplitudes ranging from less than 1 m s−1 to approximately 5 m s−1.
Nitric oxide mixing ratios near the stratopause measured by a rocket‐borne chemiluminescent detector
Authors: Horvath Jack J. , Mason Conrad J.
Published: February 2008

A direct measurement of the nitric oxide mixing ratio between 43 km and 61 km was made with a rocket‐borne chemiluminescent detector. This was the second flight in a series of two designed primarily to determine feasibility. The rocket was launched at Wallops, Island, Virginia on 19 March 1976 at 14:15 EST. The ozone‐generated background signal was monitored throughout the flight by periodically interrupting the atmospheric sample flow with a pure‐ N2 bias‐supply gas. An extensive error analysis was performed to evaluate the uncertainty in our results. The discovery of computational and calibration‐gas concentration errors required us to reanalyze the results from the first flight of this detector in 1975; the corrected results are reported here. A comparison of the results from the two flights is made.
Electric fields and conductivity in the nighttime E‐region: A new magnetosphere‐ionosphere‐atmosphere coupling effect
Authors: Banks P. M. , Yasuhara F.
Published: February 2008

Calculations have been made of the effects of intense poleward‐directed electric fields upon the nighttime ionospheric E‐region. The results show the Pedersen and Hall conductivities are substantially changed, thereby decreasing the ionospheric electrical load seen by magnetospheric sources. It appears that relatively large electric fields can exist in the absence of accompanying large field‐aligned currents, as long as the underlying ionosphere remains in darkness and/or energetic particle precipitation is absent.
A Spacelab experiment on the critical ionization velocity
Authors: Möbius E. , Boswell R. W. , Piel A. , Henry D.
Published: February 2008

Although the existence of a critical ionization velocity has been shown in laboratory experiments certain difficulties remain when one tries to scale the parameters to cosmic dimensions. These problems are discussed in the light of recent theoretical developments, and a possible experiment is described which makes use of the high orbital velocity of spacelab and the large uniform plasma through which it travels.
Nitrite photolysis as a source of free radicals in productive surface waters
Authors: Zafiriou Oliver C. , True Mary B.
Published: February 2008

Sunlight photolyzes nitrite in natural waters, producing free radicals by NO2− + HOH + hν = NO + OH + OH−. The primary and secondary radicals may react irreversibly with the medium, or regenerate nitrite as proposed for pure water. We measured net nitrite loss to estimate the irreversible component. Compositionally varied nitrite‐rich surface seawaters from the Peruvian coastal upwelling were sealed in glass bulbs, sterilized, and exposed to ambient sunlight or held in darkness. Samples showed light‐dependent nitrite losses of 5‐27% per day, providing the first field evidence for generation of inorganic free radicals in surface seawater and their interaction with the chemical milieu (∼ 90 nmole/ℓ/day). The rate in filtered samples correlated positively with initial chlorophyll a content and negatively with nitrite concentration, indicating that biogenic scavengers and nitrite may compete in a product‐determining secondary step. Although nitrate is photolyzable and was present, it did not show photochemical loss.
Thomson scatter radar detection of D‐region negative ions at Arecibo
Authors: Ganguly S. , Mathews J. D. , Tepley C. A.
Published: February 2008

The Arecibo 430 MHz radar has been used to measure D region Thomson scatter power spectra which display bandwidth and power variations with altitude and solar zenith angle which are consistent with the presence of negative ions. The negative ion‐to‐electron number density ratio (λ−), electron density, and electron‐to‐ion temperature ratio (Te/Ti) have been derived from the spectral data and presented for noontime and sunset conditions. The λ− = 1 level is found to occur near 70 km at noon and near 80 km at sunset. Values of Te/Ti in the range 1.0 to 1.5, due to probing pulse heating, were observed.
Postseismic surface deformations due to lithospheric and asthenospheric viscoelasticity
Authors: Cohen Steven C.
Published: February 2008

This paper proposes a model for postseismic surface deformations by attributing them to lithospheric and asthenospheric viscoelasticity. The model predicts that the deformations due to lithospheric viscoelasticity depend on the decrease in the effective shear modulus acting long after the lithospheric relaxation compared to that acting immediately following the earthquake. While such deformations are generally smaller than those associated with asthenospheric viscoelasticity, they occur on a shorter time scale and may be in opposite direction to both the motion occurring at the time of the earthquake and that occurring as the asthenospheric relaxation occurs.
The moment of inertia of Mars
Authors: Kaula William M.
Published: February 2008

The non‐hydrostatic contribution to the oblateness is calculated based on the single assumption that non‐hydrostatic contributions to the moments‐of‐inertia are axially symmetric about the principal axis in the direction of the Tharsis dome. The correction to J2 is thereby −2J22, in numerical value equal to that obtained by Reasenberg by a more complicated technique. The resulting C/MR² is 0.365. The error in these values depends entirely on the extent to which mass irregularities depart from axial symmetry around Tharsis, which plausibly would not be great.
Teleseismic P‐wave delay times in a major oceanic fracture zone
Authors: Rowlett Hugh , Forsyth Don
Published: February 2008

Teleseismic P‐waves were recorded by four ocean‐bottom seismographs located in the Vema fracture zone near its western intersection with the median valley of the mid‐Atlantic ridge. J‐B travel‐time residuals range from +1.31 to +1.81 sec. The largest residuals are associated with the topographic depression that forms the extension of the median valley into the fracture zone. Differences in residuals between the stations are the result of structural variations near the receivers. The differences are too large to be explained by changes in crustal thickness. Instead, low velocities in the uppermost mantle are required by the relative residuals. These low velocities may be related to the extension into the fracture zone of a narrow zone of partial melting from beneath the ridge axis.
Ultraviolet absorption spectrum of methylchloroform in the vapor phase
Authors: Vanlaethem‐Meurée N. , Wisemberg J. , Simon P. C.
Published: February 2008

Ultraviolet absorption cross sections of methylchloroform CH3CCl3 have been measured in the wavelength interval 180‐240 nm and temperature range 210‐295 K. Numerical values are given and compared with existing data at ambient temperature. Photodissociation coefficients have been calculated for altitudes between 20 and 45 km and appear to be significantly lower than generally considered. The substantial decrease in absorption cross sections observed at low temperatures and λ > 210 nm has only a minor influence on overall photodissociation coefficients. Relative contributions of photodissociation and reaction with OH radicals as potential sinks for methylchloroform at stratospheric altitudes are briefly discussed.
Some initial ISEE‐1 results on the ring current composition and dynamics during the magnetic storm of December 11, 1977
Authors: Lennartsson W. , Shelley E. G. , Sharp R. D. , Johnson R. G. , Balsiger H.
Published: February 2008

The ISEE‐1 spacecraft carries a mass spectrometer for ions with E/Q ≤ 17 keV/e. On December 11, 1977, it traversed the equatorial magnetosphere in the prenoon and dawn sectors during the early recovery phase of a magnetic storm with peak DST=−125γ. Along the dayside (inbound) leg O+ was comparable to or exceeded H+ in number density in the energy range 0.1 keV ≤ E ≤ 17 keV. The velocity distribution of O+ showed a characteristic dispersion, consistent with the ions being transported to the dayside from the dusk to midnight sector. The high‐energy slope of the H+ and O+distribution functions showed different radial dependence, with the slope of H+ being consistent with a harder component carrying most of the energy density. Along the nightside (outbound) leg the O+ density was very low outside of 5 RE, and most of the number denisty was due to the hard H+ component.
A comparison of intense electrostatic waves near fUHR with linear instability theory
Authors: Kurth W. S. , Ashour‐Abdalla M. , Frank L. A. , Kennel C. F. , Gurnett D. A. , Sentman D. D. , Burek B. G.
Published: February 2008

Intense electrostatic waves beyond the plasmapause have recently been identified at frequencies near the upper hybrid resonance frequency. In addition, the waves occur within a band at an odd, half‐harmonic of the local electron gyrofrequency. These bands of electrostatic turbulence are among the most intense waves detected within the earth’s magnetosphere. Measurements obtained with the ISEE 1 plasma wave receiver show that the intense waves appear to be intensifications of an electrostatic cyclotron harmonic band near the upper hybrid resonance frequency. A straightforward explanation of intense waves at the upper hybrid resonance frequency exists in the electrostatic multi‐cyclotron emission theory. For a broad range of plasma parameters nonconvective instability or large spatial growth rates occur within the cyclotron band encompassing the cold upper hybrid frequency. Comparison of spatial growth rate spectra with measured wave spectra shows that there is excellent qualitative agreement between the linear theory and the observed wave characteristics.
The thermal dissociation of N2O5 in N2
Authors: Connell Peter , Johnston Harold S.
Published: February 2008

The thermal decomposition of dinitrogen pentoxide (N2O5 → NO2 + NO3) has been studied in excess nitrogen between 4 × 1014 and 2.8 × 1019 molecules cm−3 and between 262 and 307 K. This reaction is an example of unimolecular reaction kinetics, catalyzed by inert gases M, and exhibiting effects of non‐equilibrium distributions over reacting energy states. Previous measurements of the limiting low‐pressure second‐order rate constant have been confirmed and extended to lower temperatures; with M = N2, the combined old and new data give ko′ = 6.1 × 10−6 exp [(− 9570 ± 200)/T] cm³ molecules−1 s−1. An estimate of the high‐pressure first‐order rate constant, k∞ = 1.78 × 1017 exp [(− 12540 ± 130)/T] s−1, was found to be lower than the previous value at 300 K, and the high‐pressure activation energy was found to be larger than the previous estimate. The problem of extrapolating unimolecular reaction data to low temperature is not simple; a general theoretical formula is presented, which can be used approximately to extrapolate these data to stratospheric conditions.
The photochemistry of N+ ions
Authors: Constantinides E. R. , Black J. H. , Dalgarno A. , Hoffman J. H.
Published: February 2008

The photochemistry of N+ ions in the daytime thermosphere is studied using the data base of the Atmosphere Explorer C Satellite and it is argued that the reaction O+ + N(²D) → O + N+ is a major source of N+ ions at altitudes between 250 and 500 km. Close agreement with measurements is obtained by postulating a rate coefficient of 1.3×10−10cm³s−1. At altitudes below 300 km, N+ is removed by reactions with O2 but at higher altitudes the reactions of N+ with O and with H are the most important chemical loss mechanisms. We derive empirical rate coefficients of 2.2×10−12cm³s−1 for N+ + O → N + O+ and of 3.6×10−12cm³s−1 for N+ + H → N + H+.
Identification of the v3 vibration‐rotation band of CF4 in balloon‐borne infrared solar spectra
Authors: Goldman A. , Murcray D. G. , Murcray F. J. , Cook G. R. , Van Allen J. W. , Bonomo F. S. , Blatherwick R. D.
Published: February 2008

Infrared solar spectra in the 850 to 1350 cm−1 region, at 0.02 cm−1 resolution, were obtained during a balloon flight made on 27 October 1978 from Alamogordo, New Mexico. Analysis of the 1275–1290 cm−1 region indicates that the atmospheric absorption lines of CH4, N2O, H2O, HNO3 and CO2 near 1283 cm−1 are superimposed on a broader absorption feature which we interpret as due to the v3 band of CF4. Fine structure of CF4 is also identified. Preliminary estimates from the sunset spectra show approximately 75 pptv CF4 near 25 km.
High‐resolution VHF radar observations of turbulence structures in the mesosphere
Authors: Röttger J. , Rastogi P. K. , Woodman R. F.
Published: February 2008

Results from a study of mesospheric turbulence, using a VHF radar with a height resolution of 150 m, are presented. Three types of turbulence structures have been identified: blobs, sheets and layers. Blobs and sheets occurred sporadically, predominantly at heights of 60–70 km. Above 70 km, layers thicker than 1 km were dominant, which were advected with the background wind. Velocity fluctuations in these structures were proportional to their thickness. The role of partial or Fresnel reflections is discussed and possibility of diffuse reflections below 70 km is noted. Problems in estimating transport coefficients from radar data are outlined.
Tropospheric‐stratospheric interaction in the major warming event of January‐February 1979
Authors: Quiroz Roderick S.
Published: February 2008

A succession of three reversals of the meridional gradient of mean stratospheric temperature during January‐February 1979 culminated in the reversal of the zonal mean arctic flow at the 10‐mb level. Strong tropospheric‐stratospheric interaction occurred in the form of coherent wave 1 and 2 height amplifications. The flow reversal, in late February, was due mainly to wave 2. In the first of the three temperature gradient reversals, there was an unusually strong development of the "Aleutian" anticyclone. The origins of this anticyclone are traced to the retrogression of height wave 1 in the troposphere and its superpositioning with wave 2 near the Greenwich meridian on 16 January, with continuing retrogression and strong amplification after this date along with the development of westward tilt with height and strong poleward heat transport.
The quiet‐time pattern of auroral arcs as a consequence of magnetospheric convection
Authors: Lassen K.
Published: February 2008

Quiet‐time patterns of discrete auroral arcs are compared with magnetospheric convection patterns for corresponding orientations of the interplanetary magnetic field. The position and orientation of upward field aligned currents predicted from the presence of shears and flow irregularities in the convection are shown to be similar to those of the auroral arcs. It is concluded that the quiet‐time patterns are optical signatures of shears and flow irregularities in the magnetospheric convection.
Jovian upper atmospheric temperature measurement by the Voyager 1 UV spectrometer
Authors: Atreya S. K. , Donahue T. M. , Sandel B. R. , Broadfoot A. L. , Smith G. R.
Published: February 2008

The first measurement of the neutral temperature in the exosphere of Jupiter is reported. The observations were carried out by the Voyager 1 Ultraviolet Spectrometer during the solar occultation phase beginning 4.5 hours after the Jupiter encounter. The range of the exospheric temperature is found to be 1450+300−250 K. The uncertainty in the determination of the temperature appears to be largely a consequence of the lack of knowledge of the brightness distribution on the solar disc at the time of the observations. The high exospheric temperature appears to result from a combination of upward propagating inertia gravity wavesmagnetospheric soft electrons and auroral electrons including those from the Io‐plasma torus.
Io's surface and environs: A magmatic‐volatile model
Authors: Hapke Bruce
Published: February 2008

A new model is proposed to account for the observed properties of Io. The crust is probably siliceousbut the outermost visible surface is composed primarily of several allotropes of elemental sulfurplus frosts of SO2H2S and S2O. The 4µm feature in Io's IR reflectance is identified as the (ν1 + ν3) band of SO2 frost. A possible source of the S is dissociation of iron sulfide brought up from the core by mantle convection. The SO2 is produced in the volcanoes and the H2S by interaction of magnetospheric protons with the surface S. Delayed luminescence from S2O could cause the post‐eclipse brightening. The orbital torus is sustained by evaporation from molten ejecta from the volcanoes. Several additional diagnostic absorption bands and two additional minor torus species are predicted by this model.
Clear air Doppler radar measurements of the vertical component of wind velocity in the troposphere and stratosphere
Authors: Peterson Vern L. , Balsley Ben B.
Published: February 2008

We discuss three techniques for using a Doppler radar to deduce the vertical component of the wind velocity in the optically clear atmosphere. These techniques involve operating the radar antenna in three different modes: 1) scanning along almucantar circles (azimuth scans), 2) scanning along vertical circles (elevation scans), and 3) leaving the antenna fixed at the zenith. Results obtained from the Chatanika, Alaska radar facility are presented which show that below about 5 km altitude, all three methods give essentially the same results. Above this altitude, the first two methods become increasingly subject to errors arising from the effect of large scale atmospheric inhomogeneities and thus give less reliable vertical velocities. The zenith method gives accurate vertical velocities for all altitudes within its range.
Discovery of a longitudinal asymmetry in the H Lyman‐alpha brightness of Jupiter
Authors: Sandel B. R. , Broadfoot A. L. , Strobel D. F.
Published: February 2008

A strong longitude variation in the midlatitude H Lyman α brightness of Jupiter has been discovered using data from the Voyager ultraviolet spectrometers. A minimum brightness of 14.4 kR was observed in the System III [1965] west longitude range 200°‐300°. The intensity rises to a broad peak of 19.6 kR near a longitude of 110°, a 36% increase over the minimum. This intensity "bulge" was observed to rotate with the planet and appeared at the same longitude during both Voyager encounters, four months apart. This is a surprising discovery; no other planet studied to date has such a characteristic and the upper levels of the Jovian atmosphere were expected to be uniform in longitude. It is likely that a longitudinal asymmetry in charged particle precipitation leads to selective heating of the upper atmosphere and increased dissociation of H2, increasing the hydrogen column abundance. The resulting increase in resonant scattering could produce the observed intensity bulge.
The low energy plasma in the Jovian magnetosphere
Authors: Belcher J. W. , Goertz C. K. , Bridge H. S.
Published: February 2008

Measurements below 6 keV from the plasma science experiment on the Voyager spacecraft show that positive ions with temperatures as low as 30 eV to several keV are observed to distances at least as great as 40 RJ in the dayside Jovian magnetosphere. When velocity determinations are possible between ∼ 10 RJ and ∼40 RJ, the plasma velocity component along the rigid corotation direction is found to be consistently less than the full corotation speed. Positive ion measurements above ∼28 keV from the low energy charged particle experiment on Voyager demonstrate the existence of positive ions with temperatures of 20‐30 keV at all distances greater than 30 RJ. Taken together, these observations suggest that the low energy plasma population from ∼30 RJ to at least 40 RJ frequently contains both a cold and a hot component. A two‐component plasma of this nature may indicate different sources, acceleration mechanisms, or time histories for the disparate components. It may also be indicative of a single acceleration mechanism which is highly energy dependent.
Seismic gap of Michoacan, Mexico
Authors: Singh S. K. , Yamamoto J. , Havskov J. , Guzmán M. , Novelo D. , Castro R.
Published: February 2008

A 150 km segment of subduction plate boundary along the Pacific coast of Mexico between the aftershock areas of the Colima earthquake (Jan. 10, 1973; Ms = 7.5) and the recent Petatlán earthquake (March 14, 1979; Ms = 7.6) has not experienced a major earthquake since 1911 and, thus, has been designated as a seismic gap. There has been considerable discussion in the scientific community about instrumenting this gap for intensive observation. An examination of the 1911 earthquake (M = 7 3/4), however, provides strong evidence that its location was about 280 km NNW of the epicenter reported by Gutenberg and Richter. Study of seismicity of Mexico in the past century gives some additional evidence that no major earthquake (M ≳ 7.5) occurred in the area. Thus, presently available evidence suggests that no large earthquake has occurred in this gap for at least the past 78 years and perhaps for as long as 178 years.
Effects of different nitrogen fertilizers on emission of nitrous oxide from soil
Authors: Breitenbeck G. A. , Blackmer A. M. , Bremner J. M.
Published: February 2008

Field studies of emissions of nitrous oxide (N2O) from a fallow soil treated with different forms and amounts of fertilizer N showed that N2O emissions from plots treated with N in the form of ammonium sulfate or urea markedly exceeded those from plots treated with the same amount of N in the form of calcium nitrate. This supports evidence from laboratory research that most of the N2O evolved from soils treated with ammonium and ammonium‐producing fertilizers is generated by nitrifying microorganisms during oxidation of ammonium to nitrate and not, as previously assumed, through reduction of fertilizer‐derived nitrate by denitrifying microorganisms. Emissions of N2O from plots treated with fertilizer N as ammonium sulfate or urea increased with the amount of N applied. Emissions of N2O in 25 days were increased 329‐524% by application of 125 kg N ha−1 as ammonium sulfate or urea and increased 1024‐1319% by the application of 250 kg N ha−1 in these forms, but these applications did not markedly increase N2O emissions after 25 days, and the fertilizer‐induced emissions of N2O‐N observed in 96 days from plots treated with ammonium sulfate or urea represented only 0.11‐0.18% of the fertilizer N applied. Emissions of N2O from plots treated with different amounts of N as calcium nitrate did not increase with the amount of N applied and were not appreciably greater than the emissions observed when no fertilizer N was added.
Possible subsurface production of carbon‐14
Authors: Zito Richard , Donahue Douglas J. , Davis Stanley N. , Bentley Harold W. , Fritz Peter
Published: February 2008

A subsurface origin of 14C is rarely considered by researchers interested in dating groundwater. Theoretically, nuclear reactions induced by emissions from U and Th nuclei can produce measurable concentrations of 14C in groundwater. Under very special conditions, calculations indicate that subsurface production might cause significant errors in dates of less than 1 × 104 years, although normally such errors should not be important until after 5 × 104 years. However, some anomalous 14C concentrations reported recently for deep groundwater may possibly be caused in part by subsurface production of 14C.
Dust in Jupiter's magnetosphere: An Io source?
Authors: Johnson T. V. , Morfill G. , Grün E.
Published: February 2008

We have investigated the possibility of removing particles from Io by interactions with the Jovian magnetosphere. We find that dust grains of about 0.1 µm radius will rapidly become charged if exposed to the ambient Jovian plasma. For particles this size in Io's volcanic plumes, the Lorentz force can overcome Io's gravity and these particles can escape. Escaping dust will be controlled by the topology of the magnetosphere and we suggest that Io derived dust may be an important source of erosive impacts on large Jovian ring particles and destructive collisions with small particles. The ring particles themselves will interact with the Jovian plasma and we suggest that coulomb scattering of plasma particles by charged dust grains may produce a plasma gap or void in the vicinity of the rings.
Rocket observations of precipitating electrons over a pulsating aurora
Authors: Sandahl Ingrid , Eliasson Lars , Lundin Rickard
Published: February 2008

Data from the third rocket of the Substorm‐GEOS series have been studied. The rocket was launched from ESRANGE on January 27, 1979 at 21.52.20 UT into a pulsating aurora.

Measurements were performed in the energy range 0‐33 keV with electrostatic analyzers and above 48 keV with solid state detectors. The pulsations are visible in the data above 3‐4 keV.

In a pulsation maximum the bulk of the energy flux is carried by electrons of energies between 5 and 40 keV. In pulsation minima the bulk of the energy flux is carried by particles of lower energies. In the electron fluxes above 25 keV a modulation of about 3 Hz is seen in the loss cone. This modulation is seen only in pulsation maxima and the modulation depth increases with increasing energy.
Martian fresh crater depths: More evidence for subsurface volatiles?
Authors: Cintala Mark J. , Mouginis‐Mark Peter J.
Published: February 2008

Shadow measurements on Viking Orbiter photography have yielded depths for 172 fresh martian craters spanning a diameter range of 0.7 to 80 km. Most craters studied are shallower than their lunar and mercurian counterparts. While the martian data exhibit a break in the depth/diameter distribution similar to those found for the Moon and Mercury, the "inflection" occurs at a smaller diameter on Mars, and the slopes below and above the break are respectively less than and greater than those of the other two planets. In addition to possible substrate‐related transient cavity modification mechanisms, flash vaporization of proposed subsurface H2O would alter the original impact‐induced velocity field by enhancing horizontal to subhorizontal target flow and excavation, thus yielding shallower craters. On the basis of the observed distribution, it is suggested that this process is more active at diameters near the break in slope (∼4 km), declining in efficiency with increasing diameter, and can account for many dissimilarities between the martian distribution and those of the Moon and Mercury, which cannot be reconciled with gravity, impact velocity, or projectile differences alone.
Long term evolution of the Lageos Orbit
Authors: Smith D. E. , Dunn P. J.
Published: February 2008

Since LAGEOS was launched in May 1976, precise laser observations of the satellite have been used to estimate relative station positions, polar motion and the earth's gravitational constant. This work was accomplished with a model of the orbit dynamics that was adequate to compute trajectories of meter level accuracy for periods of 30 days in length. Our knowledge of the long‐term evolution of the LAGEOS orbit has now been improved by an analysis of the ranging data collected during the first two years and eight months of the mission. Revisions to the originally adopted force model suggested by this work are presented in the form of the time‐histories of individual Keplerian elements. Some unexpected variations in LAGEOS orbital period are observed and clear signatures in the inclination history of this satellite, which are predominantly caused by earth and ocean tidal effects, are also described. The motion of the ascending node of the orbit suggests short‐term precisions of 1 or 2 hundredths of an arcsecond, equivalent to about a millisecond in Universal Time.
The Rattlesnake Hills of central Wyoming revisited: Further paleomagnetic results
Authors: Sheriff Steven D. , Shive Peter N.
Published: February 2008

Paleomagnetic results from the Eocene igneous rocks of the Rattlesnake Hills in central Wyoming have added 9 reliable virtual geomagnetic pole positions to previous paleomagnetic data from the area. These new data when combined with corrected results from the previous study yield a paleomagnetic pole located at 146.2° E, 79.4° N; α95 = 9.6°. This pole position, at about 44 mybp, agrees very well with other Eocene paleopole determinations for stable North America. The proximity of these pole positions to the present rotation axis shows that most of the angular distance between the apparent pole position for the Late Cretaceous and the present was closed in the Paleocene and/or early Eocene.
Preliminary results of scintillation measurements associated with ionosphere Heating and possible implications for the solar power satellite
Authors: Basu Santimay , Basu Sunanda , Johnson Allen L. , Klobuchar J. A. , Rush C. M.
Published: February 2008

Initial results of ground and air‐borne measurements of 250 MHz scintillations associated with ionospheric heating in both the overdense (heater frequency below the critical frequency) and underdense cases (heater frequency above the critical frequency) by the high‐power, high‐frequency transmitter at Platteville, Colorado are discussed. The ground stations and the geostationary satellites used in the experiment were so chosen that it was possible to explore the artificial irregularities both within and outside the central heated volume. One ground station was able to view LES‐8 in a field‐aligned direction while, at a second ground station, spaced receiver scintillation measurements were available using FLEETSATCOM. The instrumented aircraft recorded both phase and amplitude scintillations and flew missions in the north‐south and east‐west directions to define the region of artificial irregularities. The preliminary results indicate a prompt excitation of artificial irregularities in the overdense case causing 2‐10 dB scintillation at 244‐249 MHz and a lifetime of the order often minutes. In the underdense case, on the other hand, the response was delayed and effects were observed to be on the order of 1‐3 dB at 250 MHz, although a unique event of 10 dB scintillation was recorded along the field‐aligned propagation path. The presence of such scintillations in the underdense case and their implications for the proposed Solar Power Satellite (SPS) are indicated in the paper.
The dissociative recombination of vibrationally excited N2+ ions
Authors: Zipf Edward C.
Published: February 2008

The
dissociative recombination coefficient is measured for the first time as a function of the internal vibrational quantum number, v′, of the
ground state. In this plasma‐spectroscopy experiment, laser‐induced photofluorescence techniques are used to study the behavior of
ions in specifically identified vibrational and rotational quantum states. The specific dissociative recombination coefficients for the v′=0, 1, and 2 vibrational levels of the
state are found to be nearly equal in magnitude. The variation of the total
dissociative recombination coefficient with electron and vibrational temperature is given by the expression
The distribution of beryllium‐7 in the troposphere: Implications on stratospheric/tropospheric air exchange
Authors: Viezee W. , Singh H. B.
Published: February 2008

The distribution of cosmogenic beryllium‐7 (7Be) in the lower troposphere is described based on the analysis of long‐term (1973‐1979) ground level 7Be measurements. 7Be is used as a tracer of stratospheric air to suggest that the annual mean outflow of stratospheric air in the northern hemisphere can be 20 to 30% higher than in the southern hemisphere. This asymmetry is maximum during the northern hemisphere spring and reaches its peak in April. Over North America, the 7Be concentrations show a high positive correlation (linear coefficients of 0.8 to 0.9) with the occurrence of tropospheric low‐pressure troughs over several latitude belts, thus supporting the postulate that tropopause folding events, associated with low‐pressure troughs, are the dominant stratospheric/tropospheric (S/T) exchange mechanism. It is demonstrated that S/T air exchange shows a distinct seasonal variation that is highly dependent on the latitude. At midlatitudes (40‐50°N) over North America, the S/T air exchange is maximum in summer; at low altitudes (20‐30°N), it is maximum in winter and early spring. The study suggests a mechanistic model that can be used to characterize S/T air exchange at any geographical location using routinely available meteorological information.
CHClF2 (F‐22) in the Earth's atmosphere
Authors: Rasmussen R. A. , Khalil M. A. K. , Penkett S. A. , Prosser N. J. D.
Published: February 2008

Recent global measurements of CHClF2 (F‐22) are reported. Originally, GC/MS techniques were used to obtain these data. Since then, significant advances using an O2‐doped electron capture detector have been made in the analytical techniques, so that F‐22 can be measured by EC/GC methods at ambient concentrations. The atmospheric burden of F‐22 calculated from these measurements (average mixing ratio, mid‐1979, ∼45 pptv) is considerably greater than that expected from the estimates of direct industrial emissions (average mixing ratio, mid‐1979, ∼30 pptv). This difference is probably due to underestimates of F‐22 emissions.
Detection of energetic hydrogen molecules in Jupiter's magnetosphere by Voyager 2: Evidence for an ionospheric plasma source
Authors: Hamilton D. C. , Gloeckler G. , Krimigis S. M. , Bostrom C. O. , Armstrong T. P. , Axford W. I. , Fan C. Y. , Lanzerotti L. J. , Hunten D. M.
Published: February 2008

We report the discovery of energetic ( ∼ 1 MeV/nuc) H3 and H2 molecules in Jupiter’s magnetosphere. The data, obtained with the LECP instrument on Voyager 2, showed these molecules to be present throughout the magnetosphere and as far as 180 RJ from the planet, in the “magnetospheric wind” region. Although the relative abundances of H3 and H2 do not show a monotonic trend with distance from Jupiter, the intervals of highest abundance were found in the outer magnetosphere. As an example, in the radial range 51‐56 RJ of the dayside magnetosphere, the abundances of H3 and H2 (0.60‐0.95 MeV/nuc) were about 20% and 13‐25% that of He, respectively, and the He abundance was about 1‐2% that of H. Since H3+ is expected to be an important constituent of Jupiter’s ionopshere, our data provide strong evidence that, in addition to Io, the ionsphere may be an important local plasma source for the Jovian energetic particles. To our knowledge, the measurements reported here represent the first detection in nature of molecules at energies as high as 1 MeV/nucleon.
Some properties of a steady‐state geomagnetic tail
Authors: Cowley S. W. H. , Southwood D. J.
Published: February 2008

The equilibrium conditions on distended reconnected field lines in the distant geomagnetic tail are investigated on the assumption that the field line tension is balanced by tail lobe ‘mantle’ plasma convecting into the central current sheet. Subject to steady reconnection at a neutral line being possible at some point in the tail we show that steady solutions can be obtained for arbitrary down‐tail variations of mantle influx. Results are presented for a simple but physically plausible model in which the mantle density and bluk speed at the current sheet increase steadily down‐tail. Acceleration of lobe plasma in the current sheet is also discussed, and the consequent structure of the hot plasma regions down stream from the neutral line.
Magnetospheric observation of large sub‐auroral electric fields
Authors: Maynard N. C. , Aggson T. L. , Heppner J. P.
Published: February 2008

An example of large sub‐auroral poleward electric fields, similar to those observed on OGO‐6, S3‐2 and AE‐C (recently referred to as SAID) has been found in the magnetosphere near L = 4 and 2300 MLT using ISEE‐1 electric field data. The event is located adjacent to and outside the plasmapause and occurs 1½ hours into a substorm. The event is accompanied by a significant penetration of the convection electric field inside the plasmasphere. Data from similar regions on the next orbit occurring near the beginning of a substorm did not exhibit these effects. Recent theoretical models predict SAID to occur in the trough regions, where substorm dynamics force currents to flow in regions of low conductivity. These models provide a first‐order interpretation of this phenomena; however, the overall picture is more complex.
A simulation study of cold electron heating by loss cone instabilities
Authors: Ashour‐Abdalla M. , Leboeuf J. N. , Dawson J. M. , Kennel C. F.
Published: February 2008

We present results of a computer simulation study of electron cyclotron harmonic waves. We model the initial electrons velocity distribution function as a hot ring perpendicular to the ambient magnetic field and a cold Maxwellian component. We identify nonlinear cyclotron resonance as the saturation mechanism of the unstable waves and as the heating mechanism of the cold electrons.
Reformulation and discussion of mechanical behavior of the velocity‐dependent friction law proposed by Dieterich
Authors: Kosloff Dan D. , Liu Hsi‐Ping
Published: February 2008

Dieterich proposed a time and velocity‐dependent friction law that explains his experimental data for velocity‐controlled rock‐friction tests and provides some physical insight on the mechanics of stick‐slip. This law, however, is not formulated in a differential or integral form. As a consequence, numerical problems arise in applying it to the cases when the slip velocity varies continuously with time. We introduce a differential‐equation reformulation of the friction law for which the law proposed by Dieterich is a special solution. This new formulation permits precise and more generalized solution for frictional response and is of value for numerical modeling of laboratory experiments and fault mechanics in general. Two examples of solution, one for velocity‐controlled rigid slider, the other for traction‐controlled rigid slider, are given for illustration. Numerical results are compared with those obtained by Dieterich's original formulation.
Backus effect observed by Magsat
Authors: Stern D. P. , Langel R. A. , Mead G. D.
Published: February 2008

Two field models derived from Magsat data are compared, one using only field magnitude data and the other utilizing vector data as well. The difference between the two models is large and confirms the theory by Stern and Bredekamp which predicted enhanced errors in models based on intensity data alone.
Stochastic acceleration of large M/Q ions by hydrogen cyclotron waves in the magnetosphere
Authors: Papadopoulos K. , Gaffey J. D. , Palmadesso P. J.
Published: February 2008

It is shown that in hydrogen dominated multi‐ion plasmas supporting coherent hydrogen cyclotron waves, the minority ion species with large M/Q are preferentially accelerated and the maximum energy achieved scales as (M/MH+)5/3. The importance of this scaling to O+ acceleration in the auroral zones and to other high energy heavy ion observations in the earth's and Jupiter's magnetospheres is discussed.
Lidar observations of the Mount St. Helens eruption clouds over mid‐Europe, May to July 1980
Authors: Reiter R. , Jäger H. , Carnuth W. , Funk W.
Published: February 2008

Three violent eruptions of the Mount St. Helens volcano on 18 and 24 May and 13 June terminated the period of background aerosol prevailing in the stratosphere since the end of 1976, after the decay of the volcanic aerosols injected by the Fuego eruption in 1974. The Mt. St. Helens eruption cloud arrived over mid‐Europe on 26 May. The subsequent formation of a multi‐layered aerosol structure between 12 and 24 km could be observed by the ground‐based lidar at Garmisch‐Partenkirchen. The highest altitude of 24 km was reached on 30 June, the maximum scattering ratio of 4.8 at 21 km on 14 July. The scattering ratios observed indicate that the St. Helens eruption is comparable to that of Fuego in 1974.
Frequency dependence of seismic dissipation in saturated rocks
Authors: Tittmann B. R. , Nadler H. , Clark V. A. , Ahlberg L. A. , Spencer T. W.
Published: February 2008

Measurements of the specific dissipation factor, Q−1, have been made in saturated rock as a function of effective pressure. The measurements were made at two different frequencies, one in the range of 100 to 250 Hz and the other in the range of 7 to 9 kHz, using the resonant bar method. In saturated rock, Q−1 is lower at the lower frequency, and the difference between the values of Q−1 measured at the high and low frequencies decreases as effective pressure increases. At effective pressures greater than 200 bars, the Q−1 of saturated Berea sandstone measured at 200 Hz approaches that of dry Berea sandstone measured at 7 kHz.