bluuebunny/crossref_metadata_2025 huggingface dataset:
Corvid meteoroids are not ejecta from the Giordano Bruno impact
Authors: Harris A. W.
Published: February 2008

Hartung (this issue) has suggested that the Corvid meteor stream, observed only once in 1937, may be the return of a clump of ejecta from the formation of a lunar crater, specifically an event recorded in the chronicles of Gervase of Canterbury on June 25, 1178, which Hartung (1976) has previously suggested may be an eyewitness account of the formation of the lunar crater Giordano Bruno. On the basis of this association, he predicts that another Corvid shower may be observed in 2003 or 2006. In this reply, I point out three difficulties with the hypothesis: (1) it is implausible that a clump of ejecta could be launched into heliocentric orbit with a low enough dispersion in velocity among separate pieces that it would produce a meteor shower in just one year and not others; (2) subsequent perturbations by the Earth on parts of the clump passing near the Earth but not impacting, would destroy the coherence of the clump on a time scale much shorter than the 759‐year interval proposed; and (3) all else accepted, there are so many possible orbits that could yield a shower after 759 years that it is unlikely that a prediction of a return in a specific year would be correct.
Time‐variable magnetospheric radio emissions from Jupiter
Authors: Kaiser M. L.
Published: February 2008

Jupiter is the source of a large number of independent nonthermal radio sources, all of which vary with time. The known causes of the variations include planetary rotation modulation, modulation by Io and/or its torus, and influence by the solar wind which can reach surprisingly deep into the Jovian magnetosphere. However, a significant number of radio variations, both short‐term and long‐term, are not currently explained by any known mechanism.
Jupiter's winds and Arnol'd's second stability theorem: Slowly moving waves and neutral stability
Authors: Stamp Andrew P. , Dowling Timothy E.
Published: February 2008

Since the Voyager encounters in 1979, it has been known that Jupiter's cloud‐top zonal winds violate the barotropic stability criterion. A vortex‐tube stretching analysis of the Voyager wind data indicates that the more general Charney‐Stern stability criterion is also violated. On the other hand, the zonal winds determined by tracking cloud features in Hubble Space Telescope images taken in 1991 precisely match the zonal winds determined by tracking cloud features in Voyager images, and it is hard to understand how a complicated zonal wind profile like Jupiter's could be unstable and yet not change at all in 12 years. In fact, there are at least two known ways to violate the Charney‐Stern stability criterion and still have a stable flow. The better known of these is called Fjørtoft's theorem, or Arnol'd's 1st theorem for the case of large‐amplitude perturbations. Although the Fjørtoft‐Arnol'd theorem has been extended from the quasi‐geostrophic equations to the primitive equations, the basic requirement that the potential vorticity be an increasing function of streamfunction is opposite to the case found on Jupiter, where the Voyager data indicate that the potential vorticity is a decreasing function of streamfunction. But this second case is precisely that which is covered by Arnol'd's 2nd stability theorem. In fact, the Voyager data suggest that Jupiter's zonal winds are neutrally stable with respect to Arnol'd's 2nd stability theorem. Here, we analyze the linear stability problem of a one‐parameter family of sinusoidal zonal wind profiles that are close to neutral stability with respect to Arnol'd's 2nd stability theorem. We find numerically that the most unstable mode is always stationary, which may help to explain the slowly moving mode 10 waves observed on Jupiter. We find that violation of Arnol'd's 2nd stability theorem is both necessary and sufficient for instability of sinusoidal profiles. However, there appears to be no simple extension of Arnol'd's 2nd stability theorem to the primitive equations. Nevertheless, the primitive growth rates are small, and the primitive system is still governed by the quasi‐geostrophic neutral‐stability configuration.
An improved gravity model for Mars: Goddard Mars model 1
Authors: Smith D. E. , Lerch F. J. , Nerem R. S. , Zuber M. T. , Patel G. B. , Fricke S. K. , Lemoine F. G.
Published: February 2008

Doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet Mars, Goddard Mars Model 1 (GMM‐1). This model employs nearly all available data, consisting of approximately 1100 days of S band tracking data collected by NASA's Deep Space Network from the Mariner 9 and Viking 1 and Viking 2 spacecraft, in seven different orbits, between 1971 and 1979. GMM‐1 is complete to spherical harmonic degree and order 50, which corresponds to a half‐wavelength spatial resolution of 200–300 km where the data permit. GMM‐1 represents satellite orbits with considerably better accuracy than previous Mars gravity models and shows greater resolution of identifiable geological structures. The notable improvement in GMM‐1 over previous models is a consequence of several factors: improved computational capabilities, the use of optimum weighting and least squares collocation solution techniques which stabilized the behavior of the solution at high degree and order, and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models. The inclusion of X band tracking data from the 379‐km altitude, near‐polar orbiting Mars Observer spacecraft should provide a significant improvement over GMM‐1, particularly at high latitudes where current data poorly resolve the gravitational signature of the planet.
An Oceanographic Explanation for the Apparent Carbon Isotope‐Cadmium Discordancy in the Glacial Antarctic?
Authors: Broecker Wallace S.
Published: February 2008

The seeming discordance between the glacial to interglacial changes in the carbon isotope ratio and cadmium content of benthic foraminifera from the deep Antarctic has cast a shadow on the reliability of these proxies as valid of paleocirculation indicators. The problem is that while cadmium content shows little glacial to interglacial change [Lea and Boyle, 1990; Boyle, 1992], the carbon isotope change is larger than at any other place in the ocean [Curry et al., 1988; Ïññü et al., 1990;Charles and Fairbanks, 199O]. Even after correction for the 0.35‰ glacial to interglacial change in the isotope ratio for mean ocean‐atmosphere carbon, a difference of 0.5 to 0.6‰ remains. On the basis of Redfield ratios for today's ocean, this is equivalent to a 25% increase in cadmium content which is not seen. This puzzle has been with us for several years.
Influences of High‐ and Low‐Latitude Processes on African Terrestrial Climate: Pleistocene Eolian Records from Equatorial Atlantic Ocean Drilling Program Site 663
Authors: deMenocal Peter B. , Ruddiman William F. , Pokras Edward M.
Published: February 2008

High‐ and low‐latitude forcing of terrestrial African paleoclimate variability is demonstrated using 900 ka eolian and biogenic component records from Ocean Drilling Program site 663 in the eastern equatorial Atlantic. Terrigenous (eolian dust) and phytolith (savannah grass cuticle) accumulation rate records vary predominantly at 100 and 41 kyr periodicities and spectral phase estimates implicate high‐latitude forcing. The abundance of freshwater diatoms (Melosira) transported from dry African lake beds varies coherently at 23–19 kyr orbital periodicities and at a phasing which implicates low‐latitude precessional monsoon forcing. Modeling studies demonstrate that African climate is sensitive to both high‐ and low‐latitude boundary conditions. African monsoon intensity is modulated by direct insolation variations due to orbital precession, whereas remote high‐latitude forcing can be related to cool North Atlantic sea surface temperatures (SSTs) which promote African aridity and enhance dust‐transporting wind speeds. The site 663 terrigenous and phytolith records covary with North Atlantic SST variability at 41 °N (site 607). We suggest that Pleistocene African climate has responded to both high‐latitude North Atlantic SST variability as well as low‐latitude precessional monsoon forcing; the high‐latitude influence dominates the sedimentary record. Prior to circa 2.4 Ma, terrigenous variations occurred primarily at precessional periodicities (23–19 kyr), indicating that African climate was largely controlled by low‐latitude insolation variations prior to the onset of high‐amplitude glacial‐interglacial climate change.
Three‐dimensional operators acting on surface sources
Authors: Van Bladel Jean G.
Published: February 2008

This paper investigates the form which the basic operations div, grad and curl take when they are applied to sources concentrated on a surface. The “delta function” representation of single and double layers is discussed. The application to the equivalence of electric and magnetic currents is investigated in some detail.
Analysis of hemispherical dielectric resonator antenna
Authors: Luk K. M. , Leung K. W. , Lai K. Y. A. , Lin D.
Published: February 2008

This paper describes the analysis of a hemispherical dielectric resonator antenna fed by a coaxial probe. The electric field Green's function of a vertical point current located inside the dielectric hemisphere is derived by mode matching technique. Delta gap source excitation model is employed. The input impedance of the antenna is calculated using a variational formula. Both the broadside TE111 mode (the lowest‐order transverse electric mode) and the end‐fire TM101 mode (the lowest‐order transverse magnetic mode) are considered. Numerical calculations and experimental results validating the theory are shown. The variation of input resistance with dielectric constant of the antenna is studied.
Mode characteristics in chirowaveguides with dielectric lining
Authors: Mahmoud Samir F.
Published: February 2008

Mode structure in a circular chirowaveguide with dielectric lined walls is investigated. By adjusting the dielectric lining thickness and permittivity for a given chiral medium, it is possible to have the eigenmodes categorized as almost right circularly polarized or almost left circularly polarized over a wide frequency band. Such chirowaveguides with modes having high circular polarization purity can serve as feeds of reflector antennas using polarization diversity.
Nonlinear guided waves
Authors: Arnold J. M.
Published: February 2008

Nonlinear guided waves have important applications in ultrafast communication systems. These lead to new problems in electromagnetic theory which present interesting and challenging opprtunities for the development of the subject. This short review outlines the new problems which result from this development with reference to some selected but representative recent experimental work on nonlinear guided‐wave devices.
Measurement and simulation of signal fluctuations caused by propagation through trees
Authors: Durden Stephen L. , Klein Jeffrey D. , Zebker Howard A.
Published: February 2008

We present measured magnitude and phase fluctuations of UHF, L band, and C band signals that were transmitted from the ground through a forest canopy to an airborne radar. We find that the measured fluctuations are similar to those calculated by a simple Monte Carlo simulation. Both observed and calculated RMS fluctuations are typically several decibels in magnitude and tens of degrees in phase at all three frequencies.
THE Malaŵi Earthquake of March 10, 1989: DEep faulting within the East African Rift System
Authors: Jackson James , Blenkinsop Tom
Published: February 2008

Since 1964 there have been six earthquakes of Mw ≥ 5.5 in east Africa whose centroid depths have been demonstrated to be in the range of 25–40 km. These depths are significantly greater than the 5‐ to 15‐km range typical of most other regions of continental extension. The March 10, 1989 earthquake (Mw 6.1) in Malaŵi is the first such deep event to have occurred within the main topographic expression of the late Cenozoic east African rift system. Its focal mechanism and depth (32 ± 5 km) allow it to be plausibly associated with slip on a deep part of a major normal fault zone bounding the Malaŵi rift. We cannot determine whether the earthquake occurred in the crust or mantle or whether the postulated fault zone exists as a continuous seismogenic surface from the upper crust to depths of ∼30 km: it is possible that the fault zone exists as an aseismic shear zone in the lower crust. In the Malaŵi rift the width of the half graben (up to 50 km), the effective elastic thickness of the lithosphere (∼35 km), and probably the largest fault segment lengths (>50 km) are greater than is typical in rifts outside Africa. We suggest that these features and the greater earthquake depths are all related to the likelihood that the upper part of the lithosphere is colder and stronger than is typical elsewhere. These observations are consistent with earlier suggestions that normal faulting and significant strength can exist throughout the bulk of the crustal thickness. If this is the case, wide half graben can form without requiring shear strengths on the bounding faults to be greater than 1–10 MPa (10–100 bars), which is the typical level of stress drop observed in earthquakes.
Methane emission from animals: A Global High‐Resolution Data Base
Authors: Lerner Jean , Matthews Elaine , Fung Inez
Published: February 2008

We present a high‐resolution global data base of animal population densities and associated methane emission. Statistics on animal populations from the Food and Agriculture Organization and other sources have been compiled. Animals were distributed using a 1° resolution data base of countries of the world and a 1° resolution data base of land use. The animals included are cattle and dairy cows, water buffalo, sheep, goats, camels, pigs, horses and caribou. Published estimates of methane production from each type of animal have been applied to the animal populations to yield a global distribution of annual methane emission by animals. There is large spatial variability in the distribution of animal populations and their methane emissions. Emission rates greater than 5000 kg CH4 km−2 yr−1 are found in small regions such as Bangladesh, the Benelux countries, parts of northern India, and New Zealand. Of the global annual emission of 75.8 Tg CH4 for 1984, about 55% is concentrated between 25°N and 55°N, a significant contribution to the observed north‐south gradient of atmospheric methane concentration. A magnetic tape of the global data bases is available from the authors.
An Ocean Basin Scale Model of plankton dynamics in the North Atlantic: 1. Solutions For the climatological oceanographic conditions in May
Authors: Wroblewski J. S. , Sarmiento Jorge L. , Flierl Glenn R.
Published: February 2008

Mathematical equations describing marine plankton dynamics are solved for the climatological oceanographic conditions during the month of May in the North Atlantic. Geographical distributions of phytoplankton, zooplankton and limiting nutrient (nitrate) concentration in the surface mixed layer of the ocean are predicted from historical mixed layer depth and the total nutrient made locally available to the plankton ecosystem by convective mixing. The effects of major ocean currents are parameterized in the model through the geographic distribution of nitrate and its vertical gradient. Major upwelling and downwelling circulations control the proximity of high nutrient concentrations to the surface. Model solution of the phytoplankton field with 1° longitude and latitude grid resolution is compared to a recently produced composite of Coastal Zone Color Scanner images of surface chlorophyll in the North Atlantic during May 1979 [W.E. Esaias et al., 1986]. Large‐scale chlorophyll patterns seen in the CZCS composite can be explained as transition zones in the supply of plant nutrients to the surface layer by vertical mixing or localities of light limitation of phytoplankton growth by a deep mixed layer.
Methane production and oxidation in lakes impacted by the May 18, 1980 Eruption of Mount St. Helens
Authors: Lilley Marvin D. , Baross John A. , Dahm Clifford N.
Published: February 2008

The concentrations of CH4 and CH4 oxidation rates were measured in lakes impacted by the May 18, 1980 eruption of Mount St. Helens. The highest CH4 concentrations were recorded during the first summer after the eruption and ranged in surface waters from 5 μM in the moderately impacted Ryan Lake to 28 μM in the heavily impacted North Coldwater Lake. At depths below the oxic/anoxic interface, CH4 levels reached 250 μM in North Coldwater Lake, 184 μM in Spirit Lake, 70 μM in Castle Creek Lake, and 60 μM in Ryan Lake. The CH4 flux measurements from these lakes during the summer following the May 18, 1980 eruption were the highest ever recorded in lakes with ranges of 1.1–2.9 mmol CH4 m−2 d−1 in the light to moderately impacted McBride and Ryan Lakes to ranges of 17.4–25.3 mmol CH4 m−2 d−1 in the heavily impacted Castle Creek, North Coldwater, and Spirit Lakes. Evidence of CH4 oxidation was seen in all of the lakes during the summer of 1981, and rates of CH4 oxidation using 14C‐CH4 were measured in Spirit Lake from 1982 to 1986. The highest rates of CH4 oxidation measured were during the summer stratification and ranged from 50 to 150 nmol CH4 oxidized L−1 d−1. Methane oxidation rates were measured in waters having oxygen concentrations less than 100 μM with highest activity occurring at concentrations of 30–60 μM. Spirit Lake samples taken during 1986 showed a marked reduction in the levels of CH4. This has corresponded with a marked reduction in the levels of dissolved organic material in the lake and an apparent decline in sedimentary methanogenesis. The lakes heavily impacted by the eruption of Mount St. Helens, while having gone through a 2–3 year period of eutrophy following the massive input of organic wood debris and inorganic nutrients associated with ash and pyroclastic materials, are presently rapidly returning to preeruption conditions characteristic of oligotrophic, subalpine lakes.
Variations in the global air‐sea transfer velocity field of CO2
Authors: Erickson David J.
Published: February 2008

The air‐sea exchange of trace gases is critical in modeling the evolution of the compositional changes of the Earth's atmosphere on a variety of time scales. This exchange is controlled by the transfer velocity (Kw) and the air‐sea concentration gradient. The interplay between the transfer velocity and extent of local surface ocean CO2 saturation influences the partitioning of carbon and its isotopes between the atmosphere and ocean. Here, the present‐day global transfer velocity field of CO2 is computed for January and July with user‐defined derived fields based on control runs of the NCAR (National Center for Atmospheric Research) CCMl (Community Climate Model), a 12‐layer atmospheric general circulation model. The spatial resolution of these calculations is 4.5° × 7.5° latitude‐longitude. The range of KwCO2 variation over the globe is an order of magnitude, varying from 3 to 40 cm h−1. Equatorial values are generally 3–10 cm h−1 and high latitude regions experience values in excess of 30 cm h−1. The annual variability of the transfer velocity for CO2 in the high‐latitude northern hemisphere is larger than in the high‐latitude southern hemisphere. The global area‐weighted CO2 transfer velocity for both January and July runs is roughly a factor of 1.8 less than the global 14C mean.
Oceanic dimethylsulfide and marine aerosol: Difficulties associated with assessing their covariance
Authors: Bates Timothy S. , Clarke Antony D. , Kapustin Vladimir N. , Johnson James E. , Charlson Robert J.
Published: February 2008

Simultaneous measurements of oceanic dimethylsulfide (DMS), atmospheric aerosol sulfate and the size‐resolved physical properties of the aerosol were made aboard a ship in the equatorial Pacific during July 1987. Under light and variable winds, in an area essentially free of continental and anthropogenic air masses, an observed increase in oceanic DMS concentrations preceded simultaneous increases in non‐sea salt sulfate aerosol, the fraction of volatile submicrometer (sub‐μm) aerosol, the condensation nuclei population, and the mean particle diameter of the sub‐μm aerosol. Although the increase in oceanic DMS can qualitatively account for the corresponding changes in the atmospheric aerosol particles, there are numerous difficulties in quantifying the relationship between the sea‐to‐air flux of DMS and the formation and growth of atmospheric aerosol particles.
Continuous simulation models in urban hydrology
Authors: Linsley R. , Crawford N.
Published: February 2008

Continuous hydrologic simulation is defined and a simulation model is described. The information needs for urban water management systems are discussed and the use of continuous simulation of hydrologic data in meeting these information needs is reviewed. For most planning efforts data on probability of occurrence of events of various magnitudes is required and in most urban situations this can only be provided by use of a continuous simulation model.
Topside ionosphere ion heating due to electrostatic ion cyclotron turbulence
Authors: Palmadesso P. J. , Coffey T. P. , Ossakow S. L. , Papadopoulos K.
Published: February 2008

We have performed a model calculation of the ion heating rate due to electrostatic ion cyclotron turbulence in the topside ionosphere, with the assumption that the formation of a plateau on the electron velocity distribution is inhibited. Ion temperature profiles are obtained and the implications of the heating effect on anomalous resistivity calculations are discussed.
Atomic chlorine on Venus
Authors: Kumar Shailendra
Published: February 2008

The possible presence of atomic chlorine in the upper atmosphere of Venus is examined. It is suggested that a Cl abundance as low as 2 ppm will be readily detectable in far ultraviolet via 1351.7 and 1335.7 Å emissions of neutral Cl atoms. These transitions can be resonantly excited by the bright solar emission line of C+, at 1335.7 Å. It is particularly interesting to investigate atomic chlorine since the bright 1356 Å emission feature which was reported by Rottman and Moos (1973) in the Venus spectra could not be explained without requiring high concentrations of atomic oxygen. From these data, a spectroscopic upper limit of 10−4 is deduced for the mixing ratio of Cl atoms at 125 km altitude. Although we cannot justify such a large mixing ratio, it may not be unreasonable considering the uncertainties in the present understanding of chlorine photochemistry on Venus.
Stratospheric aerosol sizes
Authors: Miranda Henry A. , Fenn R.
Published: February 2008

A balloon‐borne submicron aerosol counter was successfully flown on three stratospheric balloon experiments over Holloman Air Force Base, New Mexico, in May 1973. The results indicate that particulate matter at altitudes above 23km has markedly different scattering parameters from particles at lower levels. This effect is manifested in the form of increasingly steeper size distributions and a lack of particles larger than 0.4µm diameter. The extent to which these features are attributable either to nonspherical particles or to particle index of refraction uncertainties rather than to the actual size distribution, is a matter of conjecture at this time.
Anisotropic proton instability magnetospheric (APIM) HISS: An introduction
Authors: Parady B. K.
Published: February 2008

It is proposed that some plasmaspheric ELF hiss is generated by ring current protons. The mechanism by which waves are generated is the Anisotropic Proton Instability Magnetospheric (APIM) Hiss mechanism. APIM hiss (with a frequency close to the lower hybrid resonance frequency) is a loss‐cone, flute instability arising from proton velocity space anisotropies. The energy driving the waves comes from the free energy of the "inverted population" of the proton loss‐cone distribution. The APIM hiss mechanism predicts the bandwidth, center frequency, source location, and wave normal angle of some types of plasmaspheric hiss. In addition, variation in intensity with proton anisotropies and fluxes are predicted. APIM hiss is suggested as a possible additional loss mechanism for ring current protons.
Reaction broadening of the line profiles of atomic sodium in the night airglow
Authors: Hernandez G.
Published: February 2008

The line profiles of the sodium D‐lines in the night airglow show considerable broadening which can not be ascribed to temperature alone. Based on this broadening, the known chemistry, and physics of sodium atom production in the upper atmosphere at night, we deduce that excited sodium atoms are most likely produced from the reaction of sodium monoxide and atomic oxygen, and thus find an upper limit for the dissociation energy of sodium monoxide equal to 2.89 eV (determined to a precision of 0.02 eV).
Reduced false alarm rates in seismic array detection by non‐linear beamforming
Authors: Weichert D. H.
Published: February 2008

It has been suggested that a non‐linear, multi‐channel summation process increases the signal‐to‐noise ratio of small coherent signals. Using the data base of the International Seismic Month, it is shown conclusively that a logarithmic beamforming process increases the detection probability for seismic events for a specified false alarm rate by at least a factor of two. A detector based on this process is working on‐line at the Yellowknife seismic array.
Earth Resources Satellite Systems for flood monitoring
Authors: McGinnis D. F. , Rango A.
Published: February 2008

The environmental satellites NOAA‐2 and ERTS‐1 observed flooding in United States' rivers such as the Mississippi during 1973. Combination of NOAA‐2 observation frequency and the ERTS‐1 resolution provides an adequate satellite system for monitoring floods. Several polar‐orbiting satellites of the ERTS type could view flooded areas at a reasonably high resolution every three to five days. A high‐resolution Earth‐synchronous satellite would further enhance flood mapping by providing observations whenever clouds are absent.
Electrostatic electron‐cyclotron waves with an anti‐loss‐cone distribution function
Authors: Nambu M. , Watanabe T.
Published: February 2008

High‐frequency electrostatic instabilities with an anti‐loss‐cone distribution are considered numerically. The new collective modes associated with the oscillation of the negative pressure particles appear slightly above the electron cyclotron frequency.
Least squares prediction of gravity anomalies, geoidal undulations, and deflections of the vertical with multiquadric harmonic functions
Authors: Hardy R. L. , Göpfert W. M.
Published: February 2008

Least squares prediction with MQ (multiquadric) functions is conceptually different from least squares prediction using covariance functions. MQ kernels are based on geometric or physical considerations rather than stochastic processes, and were found to be superior to covariance functions in topographic applications. This may be true also for gravity anomalies or other phenomena which result from marginally stationary, or non‐stationary random processes. The MQ harmonic kernel is used to develop a formula for estimating the best depth of point mass anomalies as a function of their number and areal extent on a sphere. Functional relationships between geoidal surface parameters are developed which provide linear equation analogs for the solution of Stokes and Vening Meinesz Integral Formulas as well as for the inversion of these classic problems. These relationships are extended to solutions at exterior equipotential surfaces.
A wave model of near wakes
Authors: Liu V. C.
Published: February 2008

A new model for the near‐wake studies is presented. It pertains to a tenuous plasma medium with negligible magnetic field effects. The wake‐generating body moves at a mesothermal speed (Vb) i.e. intermediate between the thermal speeds of ions and electrons of the ambient plasma which is bi‐thermal (Ti < Te) and has a Debye length (λD=(kTe/4πe²no)½ much smaller than the body size. The model is constructed by using the concept that the cavity left by a rapidly moving body acts as a generator of finite‐amplitude ion acoustic waves which are excited by an initial discontinuity of plasma density at the leading edge of the cavity. This ionic wave motion, represented by fluid equations, is represented approximately by the time dependent (t), one‐dimensional (x) Korteweg‐de Vries equation. The solution to the KdV equation in (x, t) variables is shown to be closely related to the stationary solution of a two‐dimensional wake in [x, z( = Vbt)] variables relative to a frame fixed to the body. Numerical and analytic solutions are both given.
Equatorial sporadic E and growth rate of associated irregularities
Authors: Rastogi R. G. , Deshpande M. R. , Sen A.
Published: February 2008

It has been shown that the sporadic E configuration observed in the ionograms from equatorial stations can suddenly appear or disappear in a time period of one minute or less. Such short decoy (or growth) times are found to agree with theoretical estimates of cross‐field instability calculations. These findings further support the identification of Es‐q to cross‐field instabilities. Attempts should be made to study the real time evolution of these irregularities by backscatter radars or finer time resolved ionosondes.
Statistical modeling of total ozone measurements with an example using data from Arosa, Switzerland
Authors: Hill William J. , Sheldon Paul N.
Published: February 2008

Statistical time series modeling was applied to the monthly average total ozone data taken at Arosa, Switzerland over the period 1932–74. The analysis led to a model that provided a significantly good representation of the Arosa data, and indicated that a much discussed decline in ozone for the first half of the 1970's is a predictable phenomenon from historical patterns in the Arosa data prior to 1970. If historical patterns persist, such as a clearly identified 133 month cycle, a return or upward trend could be expected in the late 1970's. No significant phase lag relationship could be detected between solar sunspot data and the Arosa data, nor did the sunspot periodicity seem to explain the 133 month cycle. The modeling approach is proposed as a tool for atmospheric scientists when evaluating the significance of future trends in ozone from one or a multiple of ozone recording centers around the world.
Interplanetary magnetic field fluctuations and the diurnal variation of cosmic ray intensity
Authors: Sari J. W. , Lanzerotti L. J. , Maclennan C. G. , Venkatesan D.
Published: February 2008

Predictions of the amplitudes of the diurnal variation of cosmic ray intensity, based on calculations of the power spectra of interplanetary magnetic field fluctuations, are compared with measurements of the magnitude of the diurnal variations from Sulphur Mountain neutron monitor data for five solar rotations during mid‐December 1965–April 1966, a period during which the interplanetary magnetic field data were also available. The nature of the general agreement between the derived theoretical predictions and the average observed variations over this limited period is pointed out.
Evidence for a correlation between Sun‐aligned arcs and the interplanetary magnetic field direction
Authors: Berkey F. T. , Cogger L. L. , Ismail S. , Kamide Y.
Published: February 2008

Sun‐aligned arcs are long and sometimes narrow optical structures which are oriented in the sun‐earth direction and which occur in the polar cap, generally during intervals of low magnetic activity. Their appearance, as seen by the DMSP and ISIS‐2 satellite photometers, is examined with respect to the north‐south orientation of the interplanetary magnetic field. In the DMSP pictures it is found that they appear when the IMF is directed northward. In 16 out of 18 unambiguous observations of sun‐aligned arcs by ISIS‐2, the IMF was directed northward; for the other two no IMF data was available. These results provide evidence for a strong correlation between the northward direction of the IMF and the occurrence of sun‐aligned arcs in the northern polar cap.
Low frequency radio observations of the solar wind near the Moon
Authors: Weber Richard R. , Fainberg Joseph , Stone Robert G.
Published: February 2008

The RAE‐2 lunar orbiter often measures sporadic 20‐40 dB intensity increases in the frequency range of 25‐110 kHz. Numerous examples of the disappearance of this intense noise during occultations of the sun have been observed. The average position of these occultations coincides with the average location of the plasma cavity above the nightside of the moon. We suggest that the observed high noise levels may be generated near the spacecraft by a disturbed solar wind electron population in the vicinity of the moon.
Simultaneous observations of field‐aligned currents and particle fluxes in the rost‐midnight sector
Authors: Klumpar D. M. , Burrows J. R. , Wilson Margaret D.
Published: February 2008

Simultaneous magnetic field signatures of field‐aligned currents and comprehensive charged particle measurements (5 eV ≤ E ≤ 15 keV) from the low altitude polar‐orbiting satellite ISIS‐2 are presented. The data show that in the local time sector, between 2400 and 0600 MLT, the equatorward region of outward Birkeland current flow is coincident with the region of nearly isotropic precipitation of kilovolt electrons usually associated with the low altitude termination of the plasma sheet. The poleward region of inward directed current flow is often associated with very structured fluxes of low energy electrons, some having pitch angles near 180° and often with sufficient upward flux to account for the observed current density. Variations in the intensity of the E‐W magnetic field component are usually accompanied by simultaneous changes in the spectral and pitch angle characteristics of the 5 eV to 15 keV electron fluxes. Positive ions over the above energy range carry 0.1 to 0.01 of the current carried by the electrons.
Galactic cosmic ray intensity from 1 to 9 A.U.
Authors: Van Allen James A.
Published: February 2008

The galactic cosmic ray intensity at Pioneer 10 has been compared to that at Pioneer 11 over the respective ranges of heliocentric radial distances 3.9 < r10 < 9.0 and 1.0 < r11 < 5.0 astronomical units (A.U.) during the period April 1973 — January 1976. The dominant variation is a coherent temporal one with a peak‐to‐peak amplitude of about 35 percent of the mean. A further cyclic variation of about 8 percent peak‐to‐peak has a 26‐day period and is attributed to solar‐corotating interplanetary magnetic field structures. After detailed time‐lag analysis the ratios of intensities at the two spacecraft yield a radial gradient G = +2.0 (± 0.5) percent per A. U., integral above a particle energy E = 80 MeV/nucleon and over the differential radial distance range 1.2 < (r10 ‐ r11) < 5.3 A.U.
The fate of vibrationally excited hydroxyl radicals, HO (v ≤ 9), in the stratosphere
Authors: Streit G. E. , Whitten G. Z. , Johnston H. S.
Published: February 2008

An instantaneous rate model of Ox and HOx chemistry has been used to determine the role of vibrationally excited hydroxyl radicals, HO (v ≤ 9), in the stratosphere. Due to very rapid quenching the steady state populations of vibrationally excited hydroxyl radicals are very low, (O ≤ [HO(v)] ≤ 104 molecules/cm³), and the extent of reaction due to vibrational excitation is limited.
Anomalous resistivity of the auroral plasma in the top‐side ionosphere
Authors: Ionson J. A. , Ong R. S. B. , Fontheim E. G.
Published: February 2008

Using plasma parameters from a stormtime ionospheric energy balance model, we have investigated a steady state level of electrostatic ion cyclotron turbulence. It has been determined that ion temperature anisotropy is responsible for the saturation rather than one‐dimensional ion heating. Both the electrical resistivity and ion anisotropy are evaluated as functions of altitude and field aligned Birkeland current.
A cyclonic mini‐eddy near the Blake Escarpment
Authors: Perkins H. , Wimbush M.
Published: February 2008

A small, cyclonic eddy was observed traveling eastward through three moorings of a four‐mooring array of current meters near the Blake Escarpment at 28°N. The eddy did not reach the bottom, which varied from 1200 to 5000m depth across the array, and was barely detectable at 900m. Maximum current speeds were some 40 cm/sec and the translation speed was 15‐20 cm/sec. Diameter of the strongest currents was about 15 km and total eddy diameter was 60‐80 km. The eddy appeared to be advected by the background flow. There is indirect evidence that it represents a late stage of spin‐down of a Gulf Stream ring.
Internal wave observations made with an airborne synthetic aperture imaging radar
Authors: Elachi Charles , Apel John R.
Published: February 2008

A synthetic aperture imaging radar flown on the NASA CV‐990 aircraft has yielded pictures of ocean surface features interpreted as being due to short wavelength internal waves. Wave packets similar to those detected from the Landsat‐1 satellite and other platforms have been observed off the coast of Alaska under conditions suitable for tidal excitation of internal waves. Both the radar and the Landsat images show variations in reflectivity across each wave in a packet that range from low to high to normal. The variations are evidence for the simultaneous existence of two mechanisms proposed to explain surface signatures of internal waves; roughening due to wave‐current interactions and smoothing due to slick formation. The rough region leads the smooth one in phase by one‐fourth to one‐half a wavelength.
The magnetospheric boundary layer: Site of plasma, momentum and energy transfer from the magnetosheath into the magnetosphere
Authors: Eastman T. E. , Hones E. W. , Bame S. J. , Asbridge J. R.
Published: February 2008

Observations with the Los Alamos Scientific Laboratory (LASL) plasma probe and the Goddard Space Flight Center (GSFC) magnetometer on the IMP 6 satellite show that the magnetospheric boundary layer, first identified along the flanks of the magnetosphere, is also present at the magnetosphere's sunward surface. The magnetic field lines in this sunward sector of the boundary layer are closed, and the plasma flow has a component transverse to the field. These observations suggest that the boundary layer is a site of continual transfer of plasma, momentum and energy from the magnetosheath to the magnetosphere. These transfer processes supply plasma and magnetic field to the magnetotail. Also, they produce, indirectly, the dawn‐to‐dusk electric field across the polar cap, the field‐aligned currents that border the dayside polar cap, and the soft particle fluxes that characterize the cleft precipitation, including recently reported dawn‐dusk asymmetries of these fluxes. Magnetosheath plasma directly enters the outer few hundred to few thousand kilometers of the magnetosphere's surface to form the boundary layer. There it is enabled to flow across the magnetic field (and approximately parallel to the magnetosphere's surface) by becoming electrically polarized. Leakage of the polarization charge along magnetic field lines to the earth produces the dayside high latitude effects mentioned above. The polarizing current flowing across the boundary layer interacts with the magnetic field to oppose the boundary layer plasma flow, taking up its momentum. In this way the magnetic field lines are pulled downstream. The process described here is independent of the interplanetary magnetic field (IMF) and thus may constitute the principal transfer mechanism during prolonged periods of northward IMF when the magnetosphere is very quiet. It is not clear how the effects of southward IMF are superposed on this process.
Regional basalt types in the Luna 24 landing area as derived from remote observations
Authors: Pieters Carle , McCord Thomas B. , Adams John B.
Published: February 2008

The Soviet spacecraft Luna 24 landed in Mare Crisium and returned samples that are expected to be much like the low titanium basalts from Luna 16 and Apollo 12. This conclusion is based on earth‐based spectral reflectance measurements and multispectral imagery of the Mare Crisium region and uses a background of laboratory measurements of the spectral properties of Lunar soils. These data are used to describe the regional context and composition of the Crisium basaltic units. The returned sample may also contain minor components of a high‐titanium basalt and a very low titanium basalt as well as highland material.
A study of the chemical degradation of ClONO2 in the stratosphere
Authors: Ravishankara A. R. , Davis D. D. , Smith G. , Tesi G. , Spencer J.
Published: February 2008

The flash photolysis‐resonance fluorescence technique has been utilized to measure the rate constants for the reactions of chlorine nitrate (ClONO2) with two stratospheric radicals, O(³P) and OH. Both rate constants were measured at a pressure of 20 Torr and a temperature of 245 K. The reactions with their corresponding rate constant in units of cm−3molecule−1s−1 are: O(³P) + ClONO2 → Products, k1 = (2.0 ± 0.2) × 10−13; OH + ClONO2 → Products, k2 = (3.7 ± 0.2) × 10−13.

The above results, coupled with the photolysis rate of ClONO2, indicate that these chemical degradation pathways contribute less than 10% to the removal of ClONO2 in the stratosphere.
Chevron frequency structure in Pc 1 geomagnetic pulsations
Authors: Fraser‐Smith A. C.
Published: February 2008

A new variety of fine frequency structure in Pc 1 geomagnetic pulsations is described. The structure consists of chevron‐shaped tones which, in the examples observed, have their vertices directed either all to the right or all to the left in the spectrograms of a particular pulsations event. The observations of the chevron‐structured events were made at Roberval, Quebec (L ˜ 4; geomagnetic latitude 60°). They appear to be a high‐latitude phenomenon, because no such events have been observed at Stanford, California (L ˜ 2; geomagnetic latitude 43.5°).
Comment on “Halocarbon decomposition by natural ionization”
Authors: Fehsenfeld F. C. , Albritton D. L.
Published: February 2008

The reduction in concentration of CCl4, CFCl3, and CF2Cl2 that has been reported for irradiated air samples at atmospheric pressure is reinterpreted in terms of known atmospheric electron and ion chemistry. According to this reinterpretation, the loss of these compounds that is observed at high irradiation levels, when scaled down to ionization levels appropriate to the atmosphere, supports the conclusion that ion reactions in the lower atmosphere do not constitute a significant tropospheric sink for CCl4, CFCl3, or CF2Cl2, which is contrary to the conclusion originally associated with these observations.
Lunar magnetic permeability studies and magnetometer sensitivity
Authors: King J. H. , Ness N. F.
Published: February 2008

A regression of quiet magnetic field components simultaneously measured by the two Explorer 35 magnetometers reveals uncertainties in effective sensitivity factors of up to a few percent in one or both of these instruments. Given this, the validity of previous lunar permeability studies based on Explorer 35/ALSEP regressions, wherein inferences are drawn from regression line slopes differing from unity by the order of one percent, is called into question. We emphasize the need to critically address the question of small deviations in magnetometer sensitivity factors from nominal values as a part of any two‐magnetometer lunar permeability study.
Self‐potential variations preceding earthquakes in central California
Authors: Corwin Robert F. , Morrison H. F.
Published: February 2008

Two earthquakes in central California were preceded by anomalous variations in the horizontal electric field (self‐potential) of the earth. The first variation was an anomaly of 90 mV amplitude across electrode dipoles of 630 and 640 m, which began 55 days before an earthquake of M=5, located 37 km NW of the dipoles. The second variation had an amplitude of 4 mV across a 300 m dipole, and began 110 hours before an event of M=2.4 located on the San Andreas fault, 2.5 km from the dipole. Streaming potentials generated by the flow of groundwater into a dilatant zone are proposed as a possible mechanism for the observed variations.
Stratospheric concentrations of N2O in July 1975
Authors: Krey P. W. , Lagomarsino R. J. , Schonberg M.
Published: February 2008

The first measurement of the hemispheric distribution of N2O concentrations in the lower stratosphere of the Northern Hemisphere is reported for July 1975. This distribution is similar to those of CCl3F and SF6, although N2O is more stable in the stratosphere than either of the other trace gases. The inventory of N2O in the stratosphere of the Northern Hemisphere in July 1975 against which future observations can be compared is 136 Tg.
Regional positive gravity anomaly over the Mississippi Embayment
Authors: Cordell Lindrith
Published: February 2008

A positive gravity anomaly is associated with the Mississippi embayment. When correction for low density sedimentary rocks is made the anomaly is seen to be continuous along the embayment, with an amplitude of 15 to 45 mgals increasing southward. The axis of the embayment anomaly follows the course of the Mississippi river. The seismic refraction profile critical to Ervin and McGinnis' interpretation of a fossil rift cushion underlying the embayment was located on the margin of the embayment anomaly where the structure is most complex. The continuity of the gravity anomaly indicates that a reversed refraction line along this axis, and a reflection line across it, might yield definitive results.
A study of an observed and forecasted meteorological index and its relation to the interplanetary magnetic field
Authors: Larsen Miguel Folkmar , Kelley M. C.
Published: February 2008

A study of the integrated areas of high positive vorticity (low pressure) predicted by one of the National Weather Service's prognostic models has shown a significant decrease in the accuracy of the forecast product for the time period of approximately two days following a solar sector boundary crossing. In addition, analysis of the observed integrated vorticity areas for the winter months of a three year period provided independent verification of the results obtained earlier by Wilcox et al. (1973) relative to the interplanetary magnetic field and Roberts and Olson (1973a) relative to measured geomagnetic activity. Taken as a whole, the present results suggest that short wave structures develop or exhibit growth as they are guided into the auroral or subauroral zone by global scale pressure patterns.
Evolution from oceanic to continental crust in northwestern U.S.A.
Authors: Rogers John J. W. , Novitsky‐Evans Joyce M.
Published: February 2008

Progressive thickening of the crust has occurred during the latter part of Phanerozoic time in the northwestern United States. This thickening is correlated with progressive increase in elevation relative to sea level and is probably caused by in situ aggregation of sial. Intermediate stages in the process were probably similar to the intermediate crustal structures now found in some small ocean basins.