bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for sheet‐like auroral ionospheric irregularities
Authors: Rino C. L. , Livingston R. C. , Matthews S. J.
Published: February 2008

A uniquely located, statistically prominant radiowave scintillation enhancement has been identified in nighttime auroral‐zone data. The enhancement occurs whenever the propagation path coincides with an L‐shell in the region of diffuse auroral particle precipitation. It is hypothesized that this enhancement is a purely geometric effect due to sheet‐like ionospheric irregularity structures aligned along L‐shells. This hypothesis is confirmed by spaced‐receiver data showing that the diffraction pattern is elongated along the geomagnetic east‐west direction when the scintillation enhancement occurs.
Results of a reconnaissance microearthquake survey of Bucaramanga, Colombia
Authors: Pennington Wayne D. , Mooney Walter D. , van Hissenhoven René , Meyer Hansjürgen , Ramirez J. E. , Meyer Robert P.
Published: February 2008

Six University of Wisconsin portable, continuously‐recording seismographs were operated for 3½ days in late 1976 in the Eastern Cordillera of Colombia in a 200‐km‐diameter array around Bucaramanga, where there are also three permanent stations of the Instituto Geofísico de Los Andes Colombianos. Twenty‐seven microearthquakes were recorded. Most can be well located. Only one event, located along the eastern boundary of the Eastern Cordillera, is at crustal depths. At least two events, beneath the western half of the Eastern Cordillera, are 110‐115 km in depth.

Twenty earthquakes are associated with the Bucaramanga nest (6.83°N, 73.12°W), at a depth of 158 ± 4 km. For these well‐recorded events, relative arrival times between stations vary by up to ± 0.3 sec, and the epicentral area is 4‐5 km in diameter. The complex character of these seismograms, compared with those from 110‐115 km depth events outside the nest, suggests either complexity in the rupture process or, more likely, multi‐pathing which originates near the source region.

For the upper mantle and crust above the nest, the average values for Q are about 450 for shear waves and probably over 1,000 for compressional waves, suggesting that the rays travel through lithospheric material for their entire path. If the two events at intermediate depths outside the nest and the nest lie at the same horizon within the same slab, they define a slab that strikes N‐S and dips to the east at 33°.
A preliminary report on the numerical simulation of the three‐dimensional structure and variability of atmospheric N2O
Authors: Levy H. , Mahlman J. D. , Moxim W. J.
Published: February 2008

A numerical simulation of atmospheric N2O using the GFDL 3‐D tracer model with a small uniform surface source (15 Mton yr−1) and stratospheric destruction (150 yr lifetime) has been run to a state near transport and chemical statistical equilibrium. The resulting N2O tropospheric distribution is relatively uniform with a slight excess in the Southern Hemisphere. In the model stratosphere there is a sharp poleward decrease in N2O mixing ratio away from high values in the tropics with pronounced winter minimums at 50°S and 60°N. Even with the small uniform surface source, relative standard deviations of N2O in the surface layer range from 0.1% to 0.8%, well within the range of recent measurements. Additional experiments suggest that motions acting upon N2O accumulation in the source region boundary layer and upon the mixing ratio gradient between the troposphere and lower stratosphere are the major sources of tropospheric N2O variability.
Association of low‐frequency waves with suprathermal ions in the upstream solar wind
Authors: Paschmann G. , Sckopke N. , Bame S. J. , Asbridge J. R. , Gosling J. T. , Russell C. T. , Greenstadt E. W.
Published: February 2008

Observations obtained upstream of the earth’s bow shock with the LASL/MPI plasma instruments and the UCLA magnetometers on ISEE‐1 and 2 have revealed a striking relationship between the presence of low‐frequency fluctuations in solar wind density and field strength and the different types of distribution functions of upstream ions. Waves are absent when the ions have the beamlike distribution of the “reflected” ions. Large‐amplitude waves are present only in conjunction with the “diffuse” ions, which are characterized by flat energy spectra and broad angular distributions. The waves are largely compressive, showing very good correlation between oscillations in magnetic field strength and plasma density.
Paleomagnetic stratigraphy of the Meadowcliffe Till, Scarborough Bluffs, Ontario: A Late Pleistocene excursion ?
Authors: Stupavsky M. , Gravenor C. P. , Symons D. T. A.
Published: February 2008

The 12 m thick Meadowcliffe Till was sampled in 5 vertical profiles spread horizontally over 400 m in the Scarborough Bluffs near Toronto, Ontario. This paleomagnetic study of ≃700 specimens yielded a normal segment in all 5 profiles and an excursive segment in 3 profiles. The normal zones give, in most cases, significantly different directions which suggests that they are not strictly coeval and that deposition rates in this till are highly variable from one point to the next. Overall, they give a virtual geomagnetic pole located at 273.1°W, 73.0°N (δp = 1.7°, δm = 2.6°). Similarly the 3 excursive zones are not exactly coeval. Assuming the remanence reflects a single excursion then the pole appears to swing from mid‐Africa to mid‐South Pacific, and then back to the normal Arctic pole. This polar sequence and the apparent paleofield intensities are notably similar to those found in aboriginal fireplaces at Lake Mungo, Australia. The Meadowcliffe Till is the first Ontario till to yield evidence of recording a geomagnetic field excursion(s). Accordingly its paleomagnetic age is set at 30,500 ± 1,500 yr B.P. which is within the 8,000 yr window permitted by the single radiocarbon dates from below and above the till.
Gulf Stream meanders along the Continental Margin from the Florida Straits to Cape Hatteras
Authors: Bane John M. , Brooks David A.
Published: February 2008

A rapid increase in the magnitude of Gulf Stream meanders downstream of a seaward deflection of the Stream off Charleston, South Carolina, has been indicated by an analysis of the shoreward surface thermal front of the Stream. The sixty four cases examined show that lateral movements of the Stream from Charleston to Cape Hatteras may be as great as 40 km from the mean, whereas upstream of Charleston the movements are generally less than 15 km in amplitude. This difference points to the importance of the deflection of the Stream by a bottom feature off Charleston in producing Gulf Stream meanders.
Radio emissions from the aurora
Authors: Kellogg Paul J. , Monson Steven J.
Published: February 2008

Observations are reported of radio waves in the range 2.5‐6 MHz, emitted by the aurora. Two distinct types of emissions are seen: bursts, which are broad band emissions with a time scale of the order of .1 sec, and roars, which are narrow band (300 kHz) emissions with a time scale of ten minutes.
Energetic electrons in Jupiter's dawn magnetodisc
Authors: Van Allen J. A.
Published: February 2008

Stimulated by the recent proton study of Walker, Kivelson, and Schardt, I have made a detailed reexamination of the University of Iowa data on energetic electrons during a Pioneer 10 traversal of the plasma sheet in Jupiter's dawn magnetodisc at about 51 RJ (Jupiter equatorial radii) on 6‐7 December 1973. The principal finding is that electrons of energy Ee > 0.060 MeV provide only 3 (± 0.5) percent of the charged particle pressure required to explain the observed depression in the magnetic field at the center of the plasma sheet despite the fact that the intensity of such electrons is well correlated with the depression of the magnetic pressure throughout the sheet. The contribution of energetic protons to the particle pressure is reassessed in a subsequent paper by Goertz, Parish, Van Allen, and Schardt.
Initial observations of current, temperature and coastal sea level response to atmospheric and Gulf Stream forcing on the Georgia Shelf
Authors: Lee Thomas N. , Brooks David A.
Published: February 2008

Winter observations of winds, coastal sea level and currents on the Georgia shelf indicate that low frequency currents in the inner and outer shelf regions are governed by different dynamics. Large amplitude current and temperature fluctuations at the 100 m isobath (near the shelfbreak) result primarily from events spawned by the Gulf Stream, such as northward propagating, wavelike meanders of the Gulf Stream front and cyclonic, cold‐core spin‐off eddies. Subtidal coastal sea level fluctuations appear to be a direct response to local wind forcing in the manner predicted by a frictional equilibrium model, with no indication of southward propagating continental shelf waves. The relatively wide (120 km), shallow (≈90% of shelf <50 m deep) shelf effectively isolates the inner shelf from disturbances propagating along the shelfbreak. Low frequency current variability at the 50 m isobath appears to be a mixed response to wind and Gulf Stream forcing. A conceptual model combining frictional equilibrium concepts with a meandering Gulf Stream is proposed to explain a significant portion of the observations.
Thin sheets of energetic electrons upstream from the Earth’s bow shock
Authors: Anderson K. A. , Lin R. P. , Martel F. , Lin C. S. , Parks G. K. , Rème H.
Published: February 2008

ISEE spacecraft observations show that energetic, ≥ 16 keV electrons are injected into the region upstream from the Earth’s bow shock in a thin sheet which lies just behind the sheet of interplanetary magnetic field lines that are tangent to the shock surface. Lower energy electrons leave the shock over a much broader region. Although the energetic electron intensity varies, the sheet is nearly always present and may be a quasi‐steady state feature of the bow shock. The electron velocity distribution in the thin sheet is strongly peaked and is responsible for excitation of electron plasma waves.
Do Jovian electrons influence the terrestrial outer radiation zone?
Authors: Baker D. N. , Higbie P. R. , Belian R. D. , Hones E. W.
Published: February 2008

Using energetic electron data (30 keV ‐ 2 MeV) from instruments onboard spacecraft 1976‐059A at synchronous orbit (6.6 RE), we have been able to study relatively long‐term electron flux variations. Recurrently, and often with a 27‐day periodicity, the daily average 0.2‐2.0 MeV electron spectrum hardens dramatically. This change, wherein the power law spectral index goes from γ ∼ 3‐4 to γ ≲ 2, occurs during quiet geomagnetic (low Kp) periods usually several days after the leading edge of high‐speed solar wind streams have gone past the earth. The spectral hardening is seen to be produced by a large increase in the ≳ 1 MeV electron flux; by contrast, electrons with E < 1 MeV show flux increases several days earlier than the high‐energy component and this lower energy component is in close time synchronism with high solar wind speeds. Based on nearly 2.5 years of available data, it also appears that the high‐energy electron flux may undergo an ∼ 13‐month periodicity, and for many recurrent peak intensity events we see that the flux maximum at 6.6 RE occurs ∼2 days after Jovian electron intensities have peaked outside the magnetosphere at IMP 7/8. Thus we suggest the possibility that Jovian electrons might contribute significantly at times to the terrestrial electron radiation belt population.
Origin of longitudinal grooving in Tiu VallisMars: Isolation of responsible fluid‐types
Authors: Thompson David E.
Published: February 2008

Fluid instability analysis has been developed for the growth or decay of largelongitudinal roller vortex perturbations imposed at the base of fluids of exponentially stratified viscosities. The analysis is tied to the origin of longitudinal grooving and fluting observed in a region of converging flow in Tiu VallisMars. The analysis tests the propensity of various types of fluids (watermudflow/debris flowlavaglacier)defined by their effective viscosity profilesto develop longitudinal roll patterns as part of their flow field. Fluids which allow growth of these patterns at the scale appropriate to the Mars features have the potential of creating the observed features. The details of the analysis are not presented here; ratherphysical description of assumptions used and boundary conditions imposed are discussedand the results are presented as they pertain to Tiu Vallis. It is found that the grooving pattern in Tiu Vallis has probably been formed by vortex motion in a mudflow or debris‐laden slurrybut exact representation of sediment/debris concentration or sediment transport mechanism is not yet possible. The results show that longitudinal vortex motion of the type modelled in the analysis can develop in waterlavaor icebut that the specific flow characteristics (depth or velocity) of these models which include the vortex motion are physically unreasonable for flow in Tiu Vallis.
A model of the neutral and ion nitrogen chemistry in the daytime thermosphere of Venus
Authors: Rusch D. W. , Cravens T. E.
Published: February 2008

Density profiles of N(4S)NON(²D)NO+ and N+ are calculated for the thermosphere of Venus. The results show that N(4S) is the dominant odd nitrogen species throughout the thermosphere and has a maximum density of 1.8 × 107 atoms cm−3 at 132 km. The calculated NO+ density agrees well with recent Pioneer Venus measurements but the calculated N+ densities are a factor of two to five less than the measurements. The production of N(4S) atoms generated in the model is adequate to explain recent measurements of the nitric oxide chemiluminescent emission on the night side of Venus.
Satellite observations of the spatial extent and structure of Pc 345 pulsations near the magnetospheric equator
Authors: Singer Howard J. , Russell Christopher T. , Kivelson Margaret G. , Fritz Theodore A. , Lennartsson Walter
Published: February 2008

Simultaneous observations of Pc 345 pulsations by five satellites in the pre‐noon local time sector at and near synchronous orbit are examined. The periods of these simultaneous pulsations are not the same at the different observation points. We attribute this difference to site dependent resonant conditions. The spatial properties of this temporal phenomenon are demonstrated with observations by ISEE‐1 and ‐2 as they pass through oscillations in a spatially limited region. Fundamental and second harmonic standing Alfvén waves are observed simultaneously on the same field line. The periods are consistent with model predictions when the measured plasma compositionwhich by mass consists mainly of singly ionized oxygenis taken into account.
The structure of the Jovian magnetotail from plasma wave observations
Authors: Gurnett D. A. , Kurth W. S. , Scarf F. L.
Published: February 2008

Plasma wave measurements from the outbound passes of Voyager 1 and 2 are used to study the plasma density and structure of the Jovian magnetotail. Two principal types of plasma waves are observed in the magnetotail, continuum radiation and narrowband emissions near the electron gyrofrequency. The low frequency cutoff of the continuum radiation can be used to determine the local electron density. Profiles of the electron density from the outbound passes of Voyager 1 and 2 provide evidence of a broad region of nearly uniform plasma density between the magnetopause and the inner corotating portion of the magnetosphere. We refer to this region as the boundary layer. Comparisons are made with other experimental and theoretical evidence for the existence of such a boundary layer inside the Jovian magnetosphere.
Van Der Waals molecules ‐ Possible roles in the atmosphere
Authors: Calo Joseph M. , Narcisi Rocco S.
Published: February 2008

Atmospheric equilibrium number densities are estimated for the van der Waals molecules N2 · N2, N2 · O2, O2 · O2, N2 · CO2, O2 · CO2, N2 · H2O, O2 · H2O, CO2 · CO2, H2O · H2O, A · A, A · CO2 and A · H2O for the altitude range 5‐90 km. It is concluded that number densities of atmospheric dimer species are appropriately given by equilibrium estimates, and that some are of the same order as minor, rather than trace constituents. Possible roles of van der Waals molecules in neutral and ionic ‘termolecular’ reactions, as well as infrared absorption and emission in the natural atmosphere, are proposed and examined.
Formaldehyde in remote marine air and rain: Flux measurements and estimates
Authors: Zafiriou O. C. , Alford J. , Herrera M. , Peltzer E. T. , Gagosian R. B. , Liu S. C.
Published: February 2008

The tropospheric trace constituent formaldehyde, HCHO, was measured in rain and in the gas phase during the wet season at Enewetak Atoll, a remote marine site in the central equatorial Pacific. Rainwater averaged 8 ± 2 µg/kg; the gas phase averaged 0.4 ± 0.2 ppbv (0.5 µg/m³). These values, especially the rain, are among the lowest reported to date. The formaldehyde flux to the sea by rainout and washout extrapolates to 0.010 g m−2 y−1. The gaseous flux into the sea surface is estimated to be 0.05 g m−2 y−1 by an air‐sea exchange calculation that takes into account enhanced uptake by hydroxide‐catalyzed formaldehyde hydration. The measured mixing ratio is close to the 0.18 ppbv prediction of a tropospheric chemistry model calculation. The methane oxidation chain probably is the sole formaldehyde source in the Enewetak area. The total formaldehyde flux as carbon into the ocean is ∼ 2% of the estimated total organic carbon from rainout and washout. About 2‐4% of the calculated column formaldehyde production is removed from the atmosphere by these processes.
A stratospheric source of reactive nitrogen in the unpolluted troposphere
Authors: Levy H. , Mahlman J. D. , Moxim W. J.
Published: February 2008

A GFDL 3‐D global generalized tracer field is adapted to provide a preliminary simulation of the reactive nitrogen (NOY) climatology in an unpolluted troposphere which has, as its sole source, downward transport of stratospheric NOY. The tracer field is scaled so that its downward cross‐tropopause flux is balanced by the stratospheric production of NOY. While the model results show stratospheric NOY to be a significant source for the remote troposphere, they do not rule out additional contributions from either the long‐range transport of combustion NOY or the insitu production by lightning. The model NOY climatology in the unpolluted troposphere shows a strong interhemispheric asymmetry due to greater downward NOY flux in the northern hemisphere and a steep drop off to a minimum in the tropics resulting from a combination of model features (tropical rain‐belt, ITCZ, and Indian monsoon) which have been well documented in the real atmosphere.
Melting of iron under core conditions
Authors: Brown J. M. , McQueen R. G.
Published: February 2008

Melting in iron has been detected in shock wave experiments. Release wave velocities are determined using the overtaking rarefaction technique. Upon melting the shear modulus becomes zero leading to a decrease in the acoustic wave velocity behind the shock front. Two velocity discontinuities have been detected: (1) 200 ± 2 GPa at a calculated temperature of about 4000K and (2) 250 ± 10 GPa at a calculated temperature of about 5500‐6000K. The evidence indicates that the ε‐γ transition occurs at 200 GPa and that γ iron melts near 250 GPa along the iron Hugoniot.
Theory of imperfect magnetosphere‐ionosphere coupling
Authors: Kan J. R. , Lee L. C.
Published: February 2008

A theory of magnetosphere‐ionosphere coupling in the presence of field‐aligned potential drops is formulated within the framework of magnetohydrodynamic equations. Our formulation allows the magnetosphere as well as the ionosphere to respond self‐consistently to the parallel potential drop along auroral field lines. Equipotential contours are distorted into a V‐shaped structure near the convection reversal boundary and S‐shaped on the equatorward side, each gives rise to an inverted V precipitation band. The loading effect of the imperfect coupling results in a valley in the electric field profile which occurs equatorward of the convection reversal boundary.
Far infrared measurement of stratospheric HCl
Authors: Chance K. V. , Brasunas J. C. , Traub W. A.
Published: February 2008

Thermal emission from three rotational lines of H35Cl and H37Cl was observed with a Fourier transform spectrometer from a balloon platform at 28.9 km. The measured HCl line‐of‐sight density at 1.9° elevation above 28.9 km is 4.7 ± 1.3 × 1015 cm−2, implying an average volume mixing ratio of 0.8 ± 0.2 × 10−9 at the mean sampling altitude of 32.5 km. For a uniform mixing ratio model, this corresponds to a vertical column density of 2.4 ± 0.6 × 1014 cm−2. Our result is in reasonable agreement with near infrared spectroscopic determinations and an abundance from a chemical sampling technique of HCl at this altitude; a pressure modulator radiometer measurement yields a significantly higher amount of HCl.
Energetics of long period resonant hydromagnetic waves
Authors: Greenwald R. A. , Walker A. D. M.
Published: February 2008

Recently, the STARE (Scandinavian Twin Auroral Radar Experiment) radar system has been used to measure oscillatory electric fields and latitudinal resonance widths of Pc5 toroidal mode pulsations. In this letter we use these values to determine heights‐integrated Pedersen conductivities in the resonance regions, the quality factors of the resonances, Joule heating in the ionosphere by the pulsations and magnetospheric energy storage in the resonant waves. We have found that the energy stored in a large pulsation is approximately 1% of the energy stored in the ring current. Moreover, the energy dissipated in the ionosphere by such an event can be an appreciable percentage of the equivalent dissipation by a small substorm. Assuming that the pulsation is produced by the Kelvin‐Helmholtz instability on the magnetopause or by a similar solar‐wind driven mechanism, one has a situation in which energy is transported directly from the solar wind to the ionosphere via the medium of a resonant hydromagnetic wave. Lastly, field‐aligned currents associated with this wave may be sufficient to excite topside current instabilities. Hence, we predict that poleward moving bands of auroral precipitation should be observed in association with strong pulsation events.
A significant upper limit for the rate of formation, of OCS from the reaction of OH with CS2
Authors: Iyer R. Subramonia , Rowland F. S.
Published: February 2008

The rate of reaction of OH with CS2 to form OCS by reaction (1) has been measured through observation of O14CS following 254 nm photolysis of mixtures of H2O2 with 14CS2. The OH concentrations have been monitored through simultaneous measurement in the same cell of either (a) the oxidation of CO to CO2, or (b) the removal of a hydrocarbon such as C3H8 or iso‐C4H10. The upper limit for the formation of OCS based on (a) corresponds to a rate constant k1 < 0.3 × 10−14 cm³ molecule−1 sec−1. Other chemical reactions in the system have led to the formation of both 14CO and 14CO2, indicating the existence of a complex combination of reactions such that the observed O14CS need not have been formed by (1).

The rate of reaction (1) is sufficiently slow that it is neither an important atmospheric sink for CS2 nor an important source for atmospheric OCS. The reaction of OH with OCS has not been measured in these experiments, but by analogy with k1 it is probably not an important atmospheric sink for OCS nor an important source of SO2.
Statics of the nightside Jovian plasma sheet
Authors: Lanzerotti L. J. , Maclennan C. G. , Krimigis S. M. , Armstrong T. P. , Behannon K. , Ness N. F.
Published: February 2008

We present analyses of data from the low energy charged particle (LECP) and magnetic field (MAG) experiments on the Voyager 2 spacecraft that demonstrate that the configuration of the Jovian plasma sheet at distances ∼80 to ∼120 RJ is determined by ions (protons and heavier nuclei) of energies ≳30 keV. The energy densities of these ions are sufficient to provide the diamagnetic depressions in the magnetic field strengths observed as the spacecraft crossed the Jovian plasma sheet. The particle bulk direction of motion is predominantly across the local magnetic field, consistent with that expected from corotation of the planetary magnetic field.
Is steady convection possible in the Earth's magnetotail?
Authors: Erickson G. M. , Wolf R. A.
Published: February 2008

We present a theoretical argument suggesting that steady, adiabatic convection probably cannot occur throughout a closed‐magnetic‐field‐line region that extends into a long magnetotail. If plasma in a typical flux tube in the Earth's outer plasma sheet were compressed adiabatically as it convected into the near‐Earth part of the plasma sheet, the plasma pressure would be absurdly large there. This excess‐pressure problem is demonstrated numerically for several standard models of the magnetospheric magnetic field, for the case of isotropic pressure. We argue that the excess‐pressure problem results from the general shapes of field lines in the inner and outer plasma sheet, and not from simple inaccuracies in all the magnetic‐field models. We hypothesize that sunward convection must necessarily be time‐dependent, and that the magnetospheric substorm may be the essential time‐dependent process in which plasma is suddenly and non‐adiabatically released from plasma‐sheet flux tubes.
Aspect angle dependence of irregularity phase velocities in the auroral electrojet
Authors: Ogawa T. , Balsley B. B. , Ecklund W. L. , Carter D. A. , Johnston P. E.
Published: February 2008

Long term averaged values of the electron irregularity drift velocity in the auroral electrojet obtained from VHF radar studies at Siple, Antarctica, show that the magnitude of the observed drifts is strongly range dependent. This feature is explainable in terms of the dispersion relation for the irregularity generation process, which shows that the observed irregularity phase velocity is strongly dependent on the angle between the radar beam and the earth's magnetic field. Although major features of the variations of observed drift velocity with range can be accounted for by taking this aspect angle dependency into account, best agreement between the theoretical and observed curves is obtained by assigning relatively large values to the electron collision frequency at 105 km.
On the lowest altitude S3‐3 observations of electrostatic shocks and parallel electric fields
Authors: Mozer F. S.
Published: February 2008

S3‐3 satellite observations of low altitude electrostatic shocks on auroral zone field lines indicate the presence of parallel electric fields below an altitude of 2000 km and probably below 1100 km. These conclusions result from the direct observation of parallel fields, from inference based on the V‐shaped equipotential contours associated with some shocks, and from the fact that perpendicular fields with magnitudes as large as those observed in shocks are not seen in the ionosphere.
Equatorial anomaly in the Jovian ionosphere
Authors: Mahajan K. K.
Published: February 2008

The electron concentration data from Pioneer 10 and 11 and Voyager 1 and 2 indicate the presence of equatorial anomaly in the Jovian ionosphere, with the peak electron concentration value showing a minimum near the equator.
Helium cyclotron resonance within the Earth's magnetosphere
Authors: Mauk B. H. , McIlwain C. E. , McPherron R. L.
Published: February 2008

A histogram of electromagnetic Alfven/ion cyclotron wave frequencies, sampled within the geostationary environment and normalized by the equatorial proton cyclotron frequency, shows a dramatic gap centered near the helium (He+) cyclotron frequency. Also, strongly cyclotron phase bunched helium ions (20‐200 eV) have been observed directly within the vicinity of wave environments. These observations are interpreted as resulting from the absorption of the waves through cyclotron resonance by cool ambient populations of helium ions.
Negative ion composition measurements in the stratosphere
Authors: Arijs E. , Nevejans D. , Frederick P. , Ingels J.
Published: February 2008

Composition measurements of negative ions in the stratosphere were performed at altitudes near 35 km by means of a balloon borne quadrupole mass spectrometer during two balloon flights. Some typical ion spectra are shown and discussed. The observed ions were identified as NO3−.nHNO3 and HSO4−.nHNO3.mH2SO4 clusters. Hydrated clusters of both ion families have also been detected. A reaction scheme is proposed to explain the data. The relative abundances of the ion mass peaks, as well as the measurement of minor constituents with large gas‐phase acidities, such as HNO3 and H2SO4 are briefly discussed.
Solar variability and the secular variation in the tropical tropopause
Authors: Gage Kenneth S. , Reid George C.
Published: February 2008

The height of the tropopause at tropical Pacific stations shows a marked annual variation, together with a secular variation in the annual average values. Previous authors have commented on the positive correlation between the annual average height and the sunspot number. The existence of this correlation is confirmed for the period 1952‐73, and a mechanism to relate solar activity to tropical tropopause height is proposed. The mechanism, which is a simple extension of one that will be discussed in detail elsewhere, explains the annual variation in tropopause height as a response to the annual variation in surface insolation and hence in the intensity of tropical cumulus convection and of the ascending branch of the Hadley cell. The correlation with the sunspot cycle can be explained if the solar “constant” undergoes a fractional increase of about 0.5% from solar minimum to solar maximum.
A revised magnetic polarity time scale for the Paleocene and Early Eocene and implications for Pacific plate motion
Authors: Butler R. F. , Coney P. J.
Published: February 2008

Magnetostratigraphic studies of a continental sedimentary sequence in the Clark's Fork Basin, Wyoming and a marine sedimentary sequence at Gubbio, Italy indicate that the Paleocene‐Eocene boundary occurs just stratigraphically above normal polarity zones correlative with magnetic anomaly 25 chron. These data indicate that the older boundary of anomaly 24 chron is 52.5 Ma. This age is younger than the late Paleocene age assigned by LaBrecque et al. [1977] and also younger than the basal Eocene age assigned by Ness et al. [1980]. A revised magnetic polarity time scale for the Paleocene and early Eocene is presented in this paper. Several changes in the relative motion system between the Pacific plate and neighboring plates occurred in the interval between anomaly 24 and anomaly 21. A major change in absolute motion of the Pacific plate is indicated by the bend in the Hawaiian‐Emperor Seamount chain at ∼43 Ma. The revised magnetic polarity time scale indicates that the absolute motion change lags the relative motion changes by only ∼3‐5 m.y. rather than by >10 m.y. as indicated by previous polarity time scales.
Machine stiffness appropriate for experimental simulation of earthquake processes
Authors: Kikuchi Masayuki , McNally Karen , Tittmann Bernard R.
Published: February 2008

Loading machine stiffness is considered in an attempt to simulate strain accumulation processes prior to failure in earthquakes. We impose the similarity condition that the inelastic deformation in a test specimen relative to the loading machine corresponds with that in a spherical seismic region relative to the surrounding earth. From this constraint the appropriate ratio between the stiffnesses of machine and specimen is determined to be 1.5 ∼ 2.3. Preliminary experiments were carried out for sandstone samples. A qualitative difference between acoustic emission sequences was observed depending on whether the conditions were similar or dissimilar to the earth based on the scaling assumption. In the former case, a subsidence in acoustic emission activity prior to the main fractures was clearly and systematically observed.
Effect of nitrapyrin on emission of nitrous oxide from soil fertilized with anhydrous ammonia
Authors: Bremner J. M. , Breitenbeck G. A. , Blackmer A. M.
Published: February 2008

Field studies using a chamber technique to measure emissions of nitrous oxide (N2O) showed that the N2O emissions induced by fertilization of soil with anhydrous ammonia (180 kg N ha−1) were markedly reduced by addition of nitrapyrin [2‐chloro‐6‐(trichloromethyl)‐pyridine] to this fertilizer. The emission of N2O induced by application of anhydrous ammonia in the fall was reduced 63% by addition of nitrapyrin at the rate of 0.56 kg ha−1. The corresponding reduction when nitrapyrin was added to anhydrous ammonia applied in the spring was 87%. These observations indicate that nitrapyrin has potential value for reduction of the N2O emissions induced by nitrogen fertilization of soils and the possible adverse effects of these emissions on our climate.
The auroral 214Å feature
Authors: Dalgarno A. , Victor G. A. , Hartquist T. W.
Published: February 2008

Laboratory data are used to argue that the excitation of the N II doublet near 2145 Å by electron impact on N2 occurs through the ejection of an electron from the 2sσg orbital. The cross section probably exceeds 10−18 cm², as is required if electron impact excitation of N2 is the source of the auroral feature. By extrapolation along the isoelectronic sequence, we estimate a lifetime of 5.8 ms, in harmony with recent ab initio calculations. The auroral observations then imply a rate coefficient for quenching of N+(5S2°) ions in the atmosphere of less than 10−10 cm³ s−1.
The pH of Hawaiian precipitation a preliminary report
Authors: Miller John M. , Yoshinaga Alan M.
Published: February 2008

Daily or biweekly precipitation samples have been collected at various sites on the island of Hawaii since 1974. The elevations of the sites ranged from sea level to 3400 m. Samples were analyzed on the day of collection for pH and conductivity. Detection of major anions, such as sulfate and nitrate, were made on selected samples during the period.

The pH data show a progressive increase of acidity with elevation. The sea level site averaged pH 5.2, in contrast to the sites above 2500 m, which averaged pH 4.3. It is postulated that the increase in acidity at higher levels might be explained by acidic materials, either natural or man‐made, being transported over long distances in the mid‐troposphere and being scavenged in the rain of the Hawaiian islands.
Night‐time enhancements of ionospheric electron content at L = 4 during substorms
Authors: Hargreaves John K. , Hunsucker Robert D.
Published: February 2008

Observations of the ATS‐6 radio beacon from Fairbanks show structured enhancements of the night‐time electron content during substorms. The probability of their occurrence increases with the level of magnetic disturbance, and they are most likely to be observed when the daily sum of K indices exceeds 20 in winter or 30 in summer. There is a remarkably close coincidence between these electron‐content enhancements and auroral absorption events detected by a riometer, though the relative magnitudes vary with the time of day. Electron density profiles measured with the Chatanika incoherent‐scatter radar confirm that the electron density at 90 km is enhanced during auroral absorption events. However, D and E‐region ionization is insufficient to account for the observed enhancement of the electron content, and an F‐region effect is a more likely cause. During one such event the F‐region critical frequency was 8 MHz.
ISEE‐1 observations of electrostatic shocks on auroral zone field lines between 2.5 and 7 Earth radii
Authors: Mozer F. S.
Published: February 2008

The ISEE‐1 satellite frequently passes through electrostatic shocks and the low altitude auroral particle acceleration region at geocentric radial distances less than ≈ 7 RE and as low as ≈ 2 RE. A sampling of data from the quasi‐static electric field experiment during 22 such passes revealed events (defined as regions of low frequency turbulence) containing electrostatic shocks (defined as an electric field ⩾ 100 mV/m) during 8 of the passes, which is an occurrence frequency comparable to that obtained near apogee on the S3‐3 satellite. Examination of three such electrostatic shocks shows that typical potentials of a few kV and latitudinal scale widths mapped to the ionosphere of a few km are encountered. From the latitudinal widths of the shocks and from the magnitudes of their observed electric fields, it is argued that the parallel electric field and auroral particle acceleration region may be confined to geocentric distances less than a few RE.
Thermal iron ions in high speed solar wind streams, 2. Temperatures and bulk velocities
Authors: Mitchell D. G. , Roelof E. C. , Feldman W. C. , Bame S. J. , Williams D. J.
Published: February 2008

Thermal velocities vFe = (2kT/m)½ and magnetic field‐aligned bulk flow velocity increments ΔVFe = VFe ‐ VH are estimated using the recently discovered sensitivity to iron ions in high speed solar wind streams (VH > 600 kms−1) of the NOAA/JHU Energetic Particles Experiment (EPE) on IMP 7/8. Comparison with LASL hydrogen plasma measurements and GSFC magnetometer data in several recurrent streams in 1974 reveals that O ≤ ΔVFe ≲ VA and VH ≲ vFe ≲ VA where VA is the local Alfvén velocity. These relationships for iron are consistent with those found in earlier analyses of helium and oxygen and suggest that both the heating and bulk flow of heavy ions are controlled locally by wave/particle interactions.
Lightning amplitude spectra in the interval from 100 kHz to 20 MHz
Authors: Weidman C. D. , Krider E. P. , Uman M. A.
Published: February 2008

The electric radiation fields produced by lightning return strokes, stepped leaders, and intracloud discharge processes have been Fourier‐analyzed to determine amplitude spectra for these processes from about 100 kHz to 20 MHz. The fields were recorded under conditions where the lightning locations were known and where the field propagation from the lightning sources to the recording site was entirely over salt water. The spectra for return strokes show an f−1 frequency dependence from 100 kHz to 2 MHz, an f−2 dependence between 2 and 10 MHz, and an f−5 decrease above 10 MHz. In the 1 to 20 MHz range, the spectra of the initial fast transition in return strokes, the initial fast‐rising portion of leader steps and the fast transitions in positive intracloud pulses are surprisingly similar.
The lifetime of carbonyl sulfide in the troposphere
Authors: Johnson James E.
Published: February 2008

Recently revised estimates for the photochemical loss rates of tropospheric OCS indicate that ocean hydrolysis may be the most important sink. A simple air→sea thin film transfer model, coupled with water hydrolysis indicates that the lifetime of tropospheric OCS with respect to this flux has a lower‐limit of 11 years, which yields a net lifetime for tropospheric OCS of 4‐7 years.
Refractory spherules in the Murchison Meteorite: Are they condrules?
Authors: Macdougall J. D.
Published: February 2008

Refractory spherules in the Murchison carbonaceous chondrite show a range of compositions similar to those of coexisting irregular inclusions. However, the shape and internal texture of the spherules are suggestive of formation from a liquid. The coexistance of these two types of refractory inclusions suggests that the spherules were formed by melting of previously condensed irregular inclusions. If so, they can be properly termed chondrules.
Lower hybrid acceleration and ion evolution in the suprauroral region
Authors: Chang Tom , Coppi Bruno
Published: February 2008

It is shown that ions can be accelerated perpendicularly to the magnetic field lines by resonant interactions with lower hybrid modes. Taking into account the effects of the magnetic field inhomogeneity, we demonstrate that the accelerated portion of the ions of ionospheric origin in the suprauroral region of the magnetosphere can evolve into conic distributions and propagate upwards along the field lines. Thus these ions can reach the region where they can be strongly energized along the field lines by the electrostatic shocks. We can argue that the ion distribution resulting from the combination of these accelerated ions with the background ions can depart significantly from a thermal distribution and lead to the excitation of electrostatic ion cyclotron modes.
The earthquake cycle in subduction zones
Authors: Melosh H. J. , Fleitout L.
Published: February 2008

Lithospheric plates are subducted episodically, a few meters at a time, during earthquakes. These earthquakes recur over intervals ranging from decades to centuries. Within weeks to perhaps years after such an earthquake, elastic stresses induced in the asthenosphere relax, allowing displacement and stress to propagate away from the subduction zone into the adjacent plates. Finite element modelling of this process has shown that the propagation is asymmetric, the subducted slab serves to buffer the subducting plate against extensive motion. We have constructed a simple analytic model which incorporates the effect of he subducted slab in a fundamental way. The slab's effect is modelled by a Maxwell viscoelastic element which is attached to the subducting plate. Both plates obey Elsasser's displacement propagation equations. The elastic response of the Maxwell element at first restrains the motion of the subducted plate. The plate eventually moves on the timescale of stress relaxation in the Mesosphere (hundreds to thousands of years).

The model predicts that the trench moves toward the subducting plate at an average speed of one half of the convergence rate. A strong extensional pulse is propagated into the overthrust plate shortly after the earthquake, whereas the stress pulse is small in the subducting plate. Although this extension changes into compression before the next earthquake in the cycle, the period of strong extension following the earthquake may be responsible for extensional tectonic features in the back‐arc region.
Tsunami recorded on the open ocean floor
Authors: Filloux J. H.
Published: February 2008

On March 14, 1979 a sizeable earthquake (Ms = 7.6, Richter scale) occurred on the continental shelf adjacent to S.W. Mexico, near Petatlan in the state of Guerrero. This earthquake generated a small tsunami that was recorded in deep water, 1000 km away, thus providing for the first time a glance at a tsunami traveling in the open ocean. The same sea floor pressure record displays conspicuous signals associated with vertical sea floor motions generated at the passage of the first Rayleigh seismic wave, R1. Seismic and tsunami travel velocities are in agreement with our present understanding of the phenomena, and tsunami detectability in deep water is demonstrated to be well within present day state of the art in the design of sea floor pressure transducers. As calculations anticipate, the E.M. signals associated with the passage of the tsunami were too faint to be detected.
The Moon: Its figure and orbital evolution
Authors: Binder Alan B.
Published: February 2008

A first order analysis of current selenodetic and selenochronological data indicates that the present lunar figure was formed 3.0 ± 0.5 × 109 years ago at an earth‐moon distance of 20.4 ± 2.3 earth radii. This datum and data from a variety of sources are used to define the time evolution of the earth‐moon distance. It is shown that there was a sudden increase in this distance about 2 × 109 years ago when the Q of the earth must have decreased by a factor of 5. This change in Q correlates well with the onset of rapid continental growth and hence the expansion of shallow sea‐ and continental shelf waters as shown in the geological record for that time.
Ducted auroral kilometric radiation
Authors: Calvert W.
Published: February 2008

Certain discrete, intense wave signals attributed to auroral kilometric radiation (AKR) were observed with ISEE‐1 while it was within the plasmaspheric shadow zone for direct propagation. It is believed that wave ducting by thin depletions of the plasma density aligned with the magnetic field accounts for such signals, and that their discrete nature is caused by the satellite intercepting individual ducts. These ducts, which were also observed as coincident decreases of the upper‐hybrid resonance frequency, appeared to be twenty‐percent depletions roughly one hundred kilometers across. The AKR, which is emitted approximately perpendicular to the magnetic field, apparently entered these ducts equatorward of the source after the waves had been refracted parallel to the duct axis. A diffuse background was also observed which is consistent with the leakage from similar ducts at lower L‐values. These observations establish the existence of ducted AKR, its signature on the satellite wave spectrograms, and new evidence for depletion ducts within the plasmasphere.
Latitudinal variation of the polar cusp during a geomagnetic storm
Authors: Meng Ching‐I.
Published: February 2008

Large amplitude latitudinal variation of the polar cusp position was observed during the intense geomagnetic storm of 15‐16 February 1980. The observation of the polar cusp, identified as the region of intense but extremely soft electron precipitation, was made by two nearly noon‐midnight orbit DMSP satellites over both northern and southern hemispheres. The latitudinal shift of the polar cusp is observed to be related to the intensity variation of the ring current indicated by the hourly Dst values. The polar cusp region moved from its normal location at ∼ 76° gm lat down to ∼ 62° gm lat at the peak of this storm. This movement took about 5 hours and was detected over both hemispheres. A drastic variation in the width of the cusp region was also observed; it is very narrow (∼ 1°) during the equatorial shift and expands to ≳ 5° during the poleward recovery. Variation of the polar cusp latitude with that of the Dst index was also seen during the period before the intense storm.
Defense meteorological satellite measurements of total ozone
Authors: Lovill J. E. , Ellis J. S. , Luther F. M. , Sullivan T. J. , Weichel R. L.
Published: February 2008

A multichannel filter radiometer (MFR) on Defense Meteorological Satellites (DMS) that measured total ozone on a global‐scale from March 1977 ‐ February 1980 is described. The total ozone data measured by the MFR were compared with total ozone data taken by surfaced‐based Dobson spectrophotometers. When comparisons were made for five months, the Dobson spectrophotometer measured 2‐5% more total ozone than the MFR. Comparisons between the Dobson spectrophotometer and the MFR showed a reduced RMS difference as the comparisons were made at closer proximity. A Northern Hemisphere total ozone distribution obtained from MFR data is presented.
Application of Kubelka‐Munk theory of diffuse reflectance to geologic problems: The role of scattering
Authors: Morris Richard V. , Neely Stanley C. , Mendell Wendell W.
Published: February 2008

We have used the Kubelka‐Munk theory of diffuse reflectance to learn about the manifestations of light scattering in reflectance spectra in geologically significant situations. For wavelength‐independent scattering (dimensions of the scattering centers greater than the wavelength of the incident radiation), the band depths and shapes are related to the scattering power of the medium. For wavelength‐dependent scattering (dimensions of the scattering centers comparable to or less than the wavelength of the incident radiation), additionally found were longward shifts in band minima and a general declining trend in reflectance with increasing wavelength. This effect may be responsible for the negative slope in the near‐IR reflectance spectra of the dark regions of Mars. For both kinds of scattering, nodes are observed in sets of normalized reflectance spectra when certain conditions are satisfied.