bluuebunny/crossref_metadata_2025 huggingface dataset:
The midnight temperature maximum in the Earth's equatorial thermosphere
Authors: Spencer N. W. , Carignan G. R. , Mayr H. G. , Niemann H. B. , Theis R. F. , Wharton L. E.
Published: February 2008

Using the neutral atmosphere temperature instrument on AE‐E in circular orbit at 275 km and orbit inclination 19°, we have measured the kinetic temperature of N2 throughout many orbits, providing for the first time direct in situ measurements of the diurnal temperature variation. In particular we have observed that near midnight the temperature increases substantially, sometimes to values greater than the afternoon maximum. Increases near midnight are observed about one‐half the time measurements are made showing the feature to be a persistent one. The meridional component of the neutral (N2) wind is measured simultaneously by the instrument and correlates well with the temperature maxima showing equatorward motion before midnight and poleward afterward from which we infer a pressure increase and adiabatic heating. The cause of the temperature maximum is not well established but is probably a consequence of the convergence of atmospheric flows from the dayside influenced by momentum coupling of neutral winds and ions.
On the origin of chondrules
Authors: Sonett C. P.
Published: February 2008

A new mechanism for primordial melting of chondrules based upon heating by relativistic electrons accelerated by reconnecting magnetic field lines is discussed. This mechanism is free of the creation‐annihilation problem of collisions used for heating. The basic requirements for reconnection are an interplanetary magnetic field with regions of reversals. An early mangetic field is inferred from the paleomagnetism of meteorites and the requirements of solar spin‐down, while the field reversals upon which the reconnection is based are a common property of the present epoch solar wind.
Ozone number density profiles in the lower mesosphere as determined by the French experiment on board OSO‐8
Authors: Millier F. , Vidal‐Madjar A. , Guidon J. , Roble R. G.
Published: February 2008

Solar occulation data gathered by the French solar instrument on board the OSO‐8 satellite have been used to determine the ozone number density distribution between about 50 and 70 km. The solar extinction measurements were made near the Mg II h (2803 Å) and Mg II k (2796 Å) solar emission lines. The derived ozone number density profiles at 22° and 38°N latitude during July 1975 are presented and compared with other observations and model predictions.
On the inference of properties of Saturn’s ring E from energetic charged particle observations
Authors: Thomsen M. F. , Van Allen J. A.
Published: February 2008

Assuming that Saturn has trapped radiation belts similar to those of Earth and Jupiterit is shown that observations of the radial dependence of the intensitiesenergy spectraelectron‐to‐proton intensity ratioand pitch angle distributions of energetic charged particles trapped outside of Ring A can potentially provide information (a) on the existence of Ring E(b) on the effective size of the particulate matter thereinand (c) on the magnitude of the radial diffusion coefficient for energetic particles. A parametric study of these possibilities is specialized to the characteristics of the University of Iowa detectors on Pioneer 11which will make a close encounter with Saturn in August‐September 1979.
Upstream particle events close to the bow shock and 200 RE upstream: ISEE‐1 and ISEE‐3 observations
Authors: Scholer M. , Ipavich F. M. , Gloeckler G. , Hovestadt D. , Klecker B.
Published: February 2008

We have investigated two energetic particle events (28 keV ‐ 145 keV) upstream of the earth’s bow shock with two identical experiments of the Max‐Planck‐Institut/University of Maryland on ISEE‐1 and ISEE‐3. Close to the bow shock the particle distribution is more or less isotropic and indicates strong scattering of these particles in the upstream wave field. At ISEE‐3 the particles move essentially scatter‐free from the general bow shock direction. The temporal evolution of the particle bursts is discussed in terms of the interplanetary magnetic field topology and the scattering conditions.
The annual cycle of pressure on Mars measured by Viking Landers 1 and 2
Authors: Hess S. L. , Ryan J. A. , Tillman J. E. , Henry R. M. , Leovy C. B.
Published: February 2008

Daily mean atmospheric pressures at the two Viking landers are presented for slightly more than a martian year. The seasonal variation of pressure owing to exchange of CO2 with the polar caps is quite evident and contradicts, in part, earlier theoretical results. Day‐to‐day variations are the result of passage of synoptic‐scale high and low pressure systems and are an important clue to the general circulation of the atmosphere. The effects of global dust storms on the general circulation and on the diurnal variation of pressure are detected and interpreted.
High pressure metallization of CaO: Tentative evidence
Authors: Bukowinski M. S. T. , Jeanloz Raymond
Published: February 2008

Recent shock‐wave and diamond‐cell experiments have shown that CaO transforms from the B1 to the B2 phase at 60‐70 GPa. At pressures above 100 GPa, the shock data exhibit unusually large scatter, including two datum points with densities approximately 4.5% larger than those of the B2 phase. A self‐consistent band‐structure calculation predicts that the band‐gap of CaO vanishes at approximately 2.4‐fold compression. At densities corresponding to the anomalous shock‐wave data, the predicted band gap is narrow enough to allow thermal excitation of electrons into the conduction band. Thus the large scatter may be due to thermally generated instabilities that are premonitory to a metallic or semi‐metallic state of CaO. The density excess of 4.5% is similar to the 4% increase observed upon the metallization of EuO.
Microwave radar and radiometric remote sensing measurements of lake ice
Authors: Swift C. T. , Jones W. L. , Harrington R. F. , Fedors J. C. , Couch R. H. , Jackson B. L.
Published: February 2008

Simultaneous microwave radar and spectral radiometric data were collected over Lake Erie during March 1978. A theoretical development is presented which interprets the data collected at nadir in terms of changes in the ice thickness and the electromagnetic attenuation coefficient. The theory also addresses the failure of the spectral radiometer to determine ice thickness through observations of quarter wavelength excursions in the reflectivity. Radar data collected off‐nadir showed a substantially different behavior compared to that collected near nadir. This difference is attributed to a change in propagation characteristics from quasi‐specular return from the ice‐water interface to scattering from the rough air‐ice interface.
Causes of the F region winter anomaly
Authors: Torr D. G. , Torr M. R. , Richards P. G.
Published: February 2008

Measurements made by the Atmosphere Explorer satellites are used to determine the causes of the F‐region winter anomaly, i.e., seasonal variations which result in peak electron densities which are larger in winter than in summer. It is found that for the data examined there are 3 causes of the winter anomaly. 1) Seasonal changes in neutral composition; 2) an increase in the vibrational temperature of N2 and hence in the rate coefficient for the reaction O+ (4S) + N2 → NO+ + N; 3) an increase in winter in the production of O+ (4S) due to enhanced electron quenching of O+ (²D). The presence of vibrational excitation is inferred from an increase in the rate coefficient for the reaction from winter to summer at heights above 260 km. We quantitatively demonstrate that the initial increase in electron density produced in winter by causes (1) and (2) results in an increase in the quenching of O+ (²D) thereby enhancing the source of O+ (4S) ions. We estimate that causes (1) to (3) account for ∼55%, ∼20% and ∼25% respectively of the seasonal change in O+ (4S) from summer to winter at solar minimum.
Preliminary results on the oxygen isotopic composition of the lower crust, Kilbourne Hole Maar, New Mexico
Authors: James David E. , Padovani Elaine R. , Hart Stanley R.
Published: February 2008

18O/16O ratios measured in deep crustal xenoliths from Kilbourne Hole maar, New Mexico show that the oxygen isotopic composition of the lower crust of that region is grossly heterogeneous. Xenoliths derived from similar crustal depths vary in δ18O by nearly 6‰, although the xenoliths are individually in internal oxygen isotopic equilibrium. Mafic granulites (including charnockite), probably of mantle origin, have δ18O of about 6.2 to 6.3‰ and correspondingly low 87Sr/86Sr ratios (0.703 to 0.707). Garnet granulites, apparently the residue of partial fusion of pelitic sedimentary rock, have δ18O ranging from about 9‰ to 12‰ and correspondingly high 87Sr/86Sr ratios (0.71 to 0.78).

No evidence is found for extensive oxygen exchange over large distances in the anhydrous lower crust beneath Kilbourne Hole. Absence of regional isotopic equilibrium indicates that even at melting or near melting temperatures the oxygen isotopic identity of the protolith can be preserved over long periods of time. We conclude that there is little reason to postulate that massive oxygen exchange with a mantle‐like reservoir is a general phenomenon of the lower crust.
Ice nucleus and aerosol measurements in the plume of the Johnstown, PA., steel mill
Authors: Schnell R. C. , Pueschel R. F. , Weickmann H. K. , Wellman D. L.
Published: February 2008

The Johnstown steel mill was observed to produce aerosols containing ice nuclei active at threshold temperatures between −6°C and −8°C (warmer than those observed for background air) and in concentrations up to a factor of 5 greater than background air in the temperature range of −10°C to −12°C, as tested with a combination membrane filter‐drop freezing technique. These ice nuclei were not observed in the plume at distances greater than 15 km downwind of the source.
Measurements of NO, O3, and temperature at 19.8 km during the total solar eclipse of 26 February 1979
Authors: Starr W. L. , Craig Roger A. , Loewenstein M. , McGhan M. E.
Published: February 2008

Local measurements of stratospheric NO and O3 mixing ratios and air temperature were made during the total solar eclipse of 26 February 1979. The instrumentation was carried aboard a U‐2 aircraft flown at an altitude of 19.8 km in the region near 47° N ‐ 112° W. Eclipse maximum occurred approximately in the middle of the 2‐3/4‐hr measurement period. The NO mixing ratio was reduced at least a factor of 25 at the maximum of the eclipse. The decrease and recovery of NO during the passage of the Moon's shadow over the measurement region follows approximately the predictions of two independent models. No change was observed in either the O3 mixing ratio or the air temperature that could be attributed to the eclipse.
On new scattering modes for studying plasma instabilities with a HF radar system
Authors: Hanuise C. , Crochet M.
Published: February 2008

Electron density irregularities and associated plasma instabilities in the equatorial electrojet are usually studied by looking at the direct backscattered signal. New scattering modes have been observed with a HF radar. In the first one, backscatter in the E layer occurs after reflection in the F layer. In the other one, it is possible to study simultaneously different irregularity wavelengths and to observe quasi‐horizontal plasma irregularities.
On the possible increase of the atmospheric methane and carbon monoxide concentrations during the last decade
Authors: Graedel T. E. , McRae J. E.
Published: February 2008

Various published measurements of the background concentrations of ground level atmospheric methane suggest an increase from ∼1.6 ppm to ∼1.7 ppm over the past decade. To supplement these analyses, we have analyzed ten years of continuous data from three urban/suburban sites and find that the annual minima in the monthly midmeans of daily minima follow this suggested pattern in both direction and magnitude. A similar but less well‐characterized result is obtained for carbon monoxide as well.
Polar cap F‐layer auroras
Authors: Weber E. J. , Buchau J.
Published: February 2008

Polar cap auroras were measured at Thule Air Base, Greenland in December 1979, using an all sky imaging photometer. These images combined with digital ionosonde measurements, show the orientation, structure, and drift motion of sun‐aligned, F layer auroras. Drifts in both the dawn‐to‐dusk and dusk‐to‐dawn direction were observed. These auroras were not visible on the all sky camera films; however, coincident Defense Meteorological Satellite Program (DMSP) precipitating electron measurements show that these arcs are produced by fluxes of low energy (E<500 ev) electrons. Simultaneous satellite‐to‐ground signal amplitude measurements show that these auroras are accompanied by km scale size ionospheric irregularities, which cause strong amplitude fluctuations (scintillation) on the received satellite signal.
The effect of microscopic turbulence on magnetosphere‐ionosphere coupling
Authors: Lysak Robert L. , Carlson Charles W.
Published: February 2008

The effect of turbulence on the coupling of the magnetosphere and ionosphere has been investigated by including an effective collision frequency in the electron equation of motion. When this term is combined with the continuity equation, the ion equation of motion and Maxwell’s equations, a dispersion relation for the kinetic Alfvén wave including effective collisions is found. The wave‐particle interaction leads to a strong damping of the wave. Inclusion of the effects of plasma sheet kinetics yields a scale size transverse to the magnetic field which corresponds to the size of visual auroral arcs.
Implications of natural sources for the latitudinal gradients of NOy in the unpolluted troposphere
Authors: Hameed Sultan , Paidoussis Olga G. , Stewart Richard W.
Published: February 2008

We investigate the latitudinal variations of the sources of tropospheric odd nitrogen (NOy) due to lightning discharges and stratosphere‐troposphere exchange. By also considering the latitudinal variation of the removal rate in rainout we calculate the NOy distributions in the troposphere using a one‐dimensional model. We then discuss the implications of the characteristic latitudinal gradients of NOy due to these two sources in view of the GAMETAG measurements in the free troposphere.
Simulation of the current‐driven electrostatic ion cyclotron instability
Authors: Pritchett P. L. , Ashour‐Abdalla M. , Dawson J. M.
Published: February 2008

Particle simulations are employed in a self‐consistent investigation of the growth and saturation of current‐driven instabilities along auroral field lines. Ion cyclotron waves are found to grow to levels eϕ/Te ∼ 0.2‐0.4, which are comparable with the levels observed by the S3‐3 satellite. In the present initial‐value calculations, saturation is due to plateau formation on the electron distribution function. Excitation of the ion cyclotron waves leads to moderate (∼ 40%) perpendicular heating of the ions but does not produce a high‐energy tail. The associated anomalous resistivity is relatively small, ν*/ωpe ∼ 1 × 10−4. Implications of these results for observation of ion cyclotron waves on auroral field lines are discussed.
Effects of lateral resolution on the identification of volcanotectonic provinces on Earth and Venus
Authors: Arvidson Raymond E. , Davies Geoffrey F.
Published: February 2008

Topographic data sets for the continental United States and the North Pacific have been degraded and displayed in the same manner as the Pioneer‐Venus altimeter data for Venus. Results for the U.S. data show that the Cordillera orogenic zone would be seen as a broad swell with a height of 2 km and a wavelength of about 2500 km. Individual structural elements within the Cordillera are reduced to mild (height about 700 m; wavelength about 500 km) swells that are superimposed on the broad Cordillera rise. For the Pacific data, the Hawaiian swell, the E‐W trending fractures in the Eastern Pacific, the increase in depth away from the East Pacific Rise, and most trenches, can still be discerned. The Venusian data do not show the integrated trench, transform, and ridge system evident in the degraded Pacific data. These features would be discernible in the degraded Pacific data even after correcting depths for: (a) the higher surface temperature on Venus, and (b) the lack of loading due to ocean water. Thus, a plate tectonic regime similar to Earth's does not appear to currently exist on Venus. Unfortunately, as shown by the degraded Cordillera data, the PV altimetry data are not of sufficient quality to discern whether or not the highlands of Venus preserve evidence for orogenic events related to an ancient epoch of plate tectonics.
Differential shear‐wave attenuation (δt*) across the East Pacific Rise
Authors: Schlue J. W.
Published: February 2008

SS phases from earthquakes on fracture zones near the Easter Island Cordillera and the West Chile Rise which are recorded in the United States have reflection points on either side of the East Pacific Rise (EPR) near the equator. The east‐west records from seven WWSSN stations of seven events in this region were used to obtain spectral amplitudes of horizontally polarized S and SS waves. SS‐to‐S amplitude ratios were formed, and differential attenuation (δt*) computed within the frequency band 0.01 to 0.11 Hz. The values of δt* vary between −0.1 sec and +35.8 sec for the 23 station‐event pairs used. However, the change in δt* with distance from the axis of the EPR does not reflect the smooth variation expected using a model of a simple cooling slab.
Anomalies in geomagnetic variations on peninsular India near Palk Strait
Authors: Thakur N. K. , Mahashabde M. V. , Arora B. R. , Singh B. P. , Srivastava B. J. , Prasad S. N.
Published: February 2008

Anomalies in transient geomagnetic variations have been previously studied using data from five permanent observatories in the peninsular India. The results from the three observatories falling under the equatorial electrojet showed the presence of a strong current concentration between India and Sri Lanka Island. The currents seem to flow at the depth of the crust or upper mantle. These findings have been confirmed hereby by collecting data from an array of magnetometers. We associate the channelling to the presence of a geological conductor between India and Sri Lanka Island.
Monte Carlo Simulation of charged particles upstream of the Earth's bow shock
Authors: Ellison Donald C.
Published: February 2008

A Monte Carlo simulation of a plane, parallel shock is used to model the observations of ‘diffuse’ ions upstream of the earth's bow shock. Spectra from solar wind to high energies are calculated for various forms of the diffusion coefficient and escape and an upper limit to the efficiency obtained. These results suggest that astrophysical shocks are capable of accelerating ions directly from the thermal plasma without need of a distinct pre‐energizing injection stage.
Variation with age of anisotropy under oceans, from great circle surface waves
Authors: Journet B. , Jobert N.
Published: February 2008

Global great circle measurements of regionalized mantle Love wave phase velocities are interpreted in terms of regional models. The same study had been made by J.J. Lévêque (1980) for Rayleigh waves, and the resulting models for the two oceanic regions of different ages are used as a basis for comparison : the observed Love wave dispersion cannot be explained with these models if isotropic. The models obtained by inversion of Love wave data are compared with the models mentioned; the discrepancy appearing in the 250km depth range between the velocities βH and βV of respectively SH and SV waves is indicative of polarization anisotropy. Moreover, we put forward a significant variation from young to old oceans : the difference between βH and βV is of the order of 1 % for the former, compared to 3% for the latter. This variation can bring information about the behaviour of upper mantle materials in connection with the motion of oceanic plates.
On the possibility of detecting large‐scale crustal remanent magnetization with MAGSAT vector magnetic anomaly data
Authors: Galliher S. C. , Mayhew M. A.
Published: February 2008

Magnetic anomaly component data measured by Magsat is compared with synthetic anomaly component fields arising from an equivalent source dipole array at the Earth's surface generated from total field anomaly data alone. It is found that the synthetic components fit the component data regardless of the dipole orientation assigned to the equivalent sources and of the dipole spacing. Tentative conclusions are 1) over the U.S., vector anomaly fields can be determined to the accuracy of the measurements from the total field anomaly data alone, and 2) the equivalent source technique is not useful for determining the direction of large‐scale crustal magnetization.
An evaluation of heat flow and its geological implications on Mt. St. Helens
Authors: Grady T. , Brown R. L. , Adams E. , Sato A.
Published: February 2008

A study to determine the heat flux pattern in the vicinity of Mt. St. Helens was undertaken as part of a program to evaluate the effects of the eruption on future snowpack conditions in the area. Subsurface temperature and low energy refraction seismic studies were made during the early spring in 1981 to determine both the heat flux in the area of pyroclastic deposition and its potential source. In addition, samples were collected for later laboratory determination of thermal conductivity and diffusivity. Results indicate that the heat flow values in the area of pyroclastic deposition are as large as forty times greater than the heat flow values measured on Mt. Adams and Mt. Hood during the same period. The highest heat flow values appear to coincide with a pumice flow unit on the north side of the mountain. Comparison with work done on the eruption of Mt. Komagatake indicates that the large heat flow values may continue for several years.
Neutral temperature and electron‐density measurements in the lower E region by vertical HF sounding in the presence of an acoustic wave
Authors: Blanc Elisabeth
Published: February 2008

An acoustic wave generated at ground level and propagating vertically through the lower ionosphere produces partial reflections of radio waves transmitted by a vertical sounder. The Doppler effect of the radio wave, produced by the acoustic wave motion, depends on the properties of the ionosphere and of the atmosphere. We show that this permits the determination of both the neutral‐temperature and the electron‐density profiles of the lower E region. The accuracy and the advantages of this method are discussed, and some experimental results are compared with those of other measurement techniques.
Reverse draping of magnetic field lines in the boundary layer
Authors: Hones E. W. , Sonnerup B. U. O. , Bame S. J. , Paschmann G. , Russell C. T.
Published: February 2008

ISEE satellite measurements of magnetic fields in the boundary layer of the earth's magnetosphere have revealed an unexpected orientation of the field lines there that may be indicative of a ‘reverse draping.’ In many crossings of the north dawn boundary of the magnetosphere the direction of the boundary layer field lines was such as to suggest that northern high latitude segments of those field lines were being pulled tailward by the boundary layer plasma faster than were their equatorial segments. The observations are compatible with the view that plasma entry occurs at high latitudes (around the cusps) and that the field aligned current source is at high, rather than near‐equatorial, latitudes. Three‐dimensional plasma flow measurements made with the ISEE satellites showed the tailward flow in the boundary layer to have an equatorward component and this also suggests high latitude entry of plasma. Simultaneous magnetic field measurements with ISEE‐1 and 2 during a sequence of boundary crossings provided determinations of the electric currents in the boundary layer and at its interfaces with the plasma sheet and the magnetosheath. these currents were found to be largely field‐aligned and to have intensities in the range 3‐6 × 10−2 μA/m².
Doppler radar observations of triggered lightning
Authors: Lhermitte Roger
Published: February 2008

A vertically pointing Doppler radar was installed approximately 50 meters from an instrumented platform where lightning is constrained to strike and where the lightning current is recorded. The experiments were designed to study the effect of lightning on the surrounding precipitation but no discernable disturbance of the precipitation particle velocity or radar reflectivity was ever detected in any of the 39 radar observed events. However, well‐defined Doppler spectra attributed to transient lightning channel echoes were occasionally observed. These data suggest that a sustained lightning continuing current is required to allow a persistent radar return from the channel and, therefore, the observation of a well‐defined Doppler spectrum. The sidebands observed in the lightning Doppler spectrum can be interpreted in terms of a modulation of the radar echo associated with the time variations of the continuing current noticeable in the recordings.
The spokes in Saturn's rings: A critical evaluation of possible electrical processes
Authors: Weinheimer Andrew J. , Few Arthur A.
Published: February 2008

Among the mechanisms proposed to explain the novel spoke phenomenon occurring in Saturn's B‐ring, the alignment of particles by an electric field has been suggested. In this and related theories, the particles are assumed to be adequately conducting; or at least it is the case that electrical conductivity generally acts to enhance the feasibility of the proposed processes. These ideas are appraised in light of the fact that the particles are most likely composed of ice. We conclude that the electrical torque required to align the particles is many orders of magnitude larger than that which is likely to exist. Also, the conductivity of ice at ring temperatures is probably so small as to inhibit some of the proposed processes.
Flute mode waves near ωLH excited by ion rings in velocity space
Authors: Cattell Cynthia , Hudson Mary
Published: February 2008

Discrete emissions at the lower hybrid frequency are often seen on the S3‐3 satellite. Simultaneous observation of perpendicularly heated ions suggests that these ions may provide the free energy necessary to drive the instability. Studies of the dispersion relation for k∥ = 0 modes excited by warm ion rings in velocity space show that waves are excited with real frequencies near the lower hybrid frequency and with growth rates ranging from ∼0.01 to 1 times the ion cyclotron frequency. Numerical results are therefore consistent with the possibility that the observed ions are the free energy source for the observed waves.
Departure from corotation of the Io plasma torus: Local plasma production
Authors: Pontius D. H. , Hill T. W.
Published: February 2008

The departure of the Jovian magnetosphere from rigid corotation is adequately explained by outward plasma transport at distances L ≳ 10. The departure of 5% observed in the Io plasma torus, however, is too large to be accounted for simply by plasma transport. We propose local plasma production to be the main factor determining the corotation lag in the torus. We calculate the outward pick‐up current provided by ionization of neutral atoms and relate this to the current produced in the ionosphere by the corotation lag. This leads to an expression giving the corotation lag of the torus as a function of radial distance. Charge transfer is found to be an important process, allowing the majority of the torus mass to be ejected from the magnetosphere in a neutral state. Thus, the mass loading rate is found to be several times that inferred from examination of the corotation lag associated with outward plasma transport.
Quadrupole convection in the lower mantle?
Authors: Busse F. H.
Published: February 2008

Global gravity data and seismic inferences of lateral inhomogeneities in the density distribution of the Earth's mantle provide information on convection in the lower mantle. The data are interpreted in terms of a model of mantle convection with two layers separated by the interface corresponding to the 670 km seismic discontinuity. It is shown that the observations are in approximate agreement with theoretical deductions for a ℓ = 2 convection mode in the lower mantle.
Heating of thermal ionospheric electrons by suprathermal electrons
Authors: Stamnes K. , Rees M. H.
Published: February 2008

Several investigators have computed ionospheric electron heating rates in the past using an incorrect term in the expression for the energy transfer from the suprathermal to the thermal electrons derived by Mantas [1975]. This incorrect formulation was also based on an electron energy loss rate inversely proportional to the suprathermal electron energy, limiting its application to energies above about 2‐3 eV. Since the proper low‐energy cutoff is the cross‐over energy at which the thermal electron intensity equals the suprathermal one, a considerable portion of the ambient electron heating may take place below 2‐3 eV, depending on the ionospheric conditions. Mantas [1981] has amended these inadequacies, but has not explored their geophysical consequences. Comparing electron heating rates and electron temperatures computed by the incorrect approach with identical computations based on the proper energy transfer term, energy loss rate and cross‐over energy, we find that the previous approach leads to a substantial underestimate of the ambient electron heating rate as well as the resulting ionospheric electron temperature. This underestimate is more pronounced for solar minimum than for solar maximum conditions as could be anticipated since the elevated electron densities and temperatures at solar maximum lead to a higher cross‐over energy and thus a lesser impact of the inadequacies in previous treatments.
Comparison of tropopause height and frontal boundary locations based on radar and radiosonde data
Authors: Larsen M. F. , Röttger J.
Published: February 2008

In February of 1982 the SOUSY‐VHF‐Radar, located near Hannover, West Germany, was operated during the passage of a warm front. The timing of the radiosonde ascent from nearby Hannover was such that the narrow frontal zone boundary was immediately overhead at a height of approximately 7 km. The data from this event has made it possible to make a detailed comparison of the radar and radiosonde reflectivity data that has not been possible before. We find that the frontal boundary that is detected by the radar appears as a very low tropopause height in the radiosonde data (approximately 3 km less than the mean during this time).
Detached plasma in Saturn's front side magnetosphere
Authors: Goertz C. K.
Published: February 2008

We discuss plasma observations in the outer front side Saturnian magnetosphere which indicate the existence of dense flux tubes outside the plasma sheet. We suggest that flux tubes are detached from the plasma sheet by a centifugally driven flute instability. The same instability leads to a dispersal of Titan‐injected plasma. It is shown that the detached flux tubes will probably break open as they convect into the nightside magnetotail and lose their content in form of a planetary wind.
Evidence for helical kink instability in the Venus magnetic flux ropes
Authors: Elphic R. C. , Russell C. T.
Published: February 2008

Empirical models of the magnetic field structure of flux ropes found in the Venus ionosphere indicate that ropes are unstable to long wavelength (> 100 km) helical kink perturbations. The onset of such an instability can explain the apparent volume distribution of flux ropes with altitude, and their orientation as a function of altitude. In the subsolar region, the fraction of volume that is occupied by flux ropes increases from roughly 20% at high altitudes to more than 50% at low altitudes, which is a greater increase than would be expected if ropes convect downward as simple straight horizontal cylinders. The helical kink instability increases the fractional volume occupied by ropes by turning the originally straight, horizontal flux tubes into corkscrew‐shaped structures as they convect to lower altitudes. This instability also explains why high altitude ropes tend to be horizontal and low altitude ropes appear to have almost any orientation. Specifically, the orientation distribution of low altitude subsolar ropes suggests a 70° average helical kink pitch, which agrees with the pitch obtained from the fractional volume increase.
Measurements of stratospheric SO2 after the El Chichón eruptions
Authors: Vedder James F. , Condon Estelle P. , Inn Edward C. Y. , Tabor Kevin D. , Kritz Mark A.
Published: February 2008

Samples of stratospheric trace gases were obtained on eight flights of NASA high‐altitude aircraft from April 16 through December 13, 1982. The sampling occurred at altitudes from 15 to 22 km, latitudes from 23° to 52° N, and longitudes from 108° to 130° W. The cryogenically concentrated samples were analyzed by gas chromatography for SO2, a primary precursor of the gas‐to‐particle conversion process. The measured mixing ratio of SO2 varied between 8 and 132 pptv. Evidence from aerosol measurements indicates that a few of our early samples may have been collected in the fringes of the volcanic cloud from El Chichón. Samples obtained on some later flights may have been from the eruption cloud but were taken at times when most of the volcanically injected SO2 should have been converted to H2SO4.
The 1982‐83 warm episode in the California Current
Authors: Lynn Ronald J.
Published: February 2008

The Warm Episode (El Niño) of 1982‐83 has produced elevated steric height (geopotential anomaly) along the coast of California and Baja California. Fifty percent of the stations observed during a survey in February and March had the greatest steric height observed for this season for the entire 33 years of California Cooperative Oceanic Fisheries Investigations (CalCOFI) observations. Where it occurred onshore, along central California in early February, this anomalous height was balanced by a strong countercurrent. Along Baja California in late March the greatest steric height was offshore and hence produced a strong equatorward flow. These conditions may not have been synoptic. An offshore shift in the subsurface thermal anomaly between January and May suggests a reversal of the flow within this time frame.
Photographic observations of Earth's airglow from space
Authors: Mende S. B. , Banks P. M. , Nobles R. , Garriott O. K. , Hoffman J.
Published: February 2008

Observations of Earth’s airglow from a recent flight of the Space Shuttle have provided new information about emissions in the visible and near infrared portions of the optical spectrum. A new type of image intensifier camera system was carried aboard STS‐5, flown in November, 1982. This instrument, which included an objective ruled grating, provided a low resolution, spectrally dispersed image of the limb airglow layer. From the resulting spectra we can identify several characteristic airglow emissions. These include the 5577 Å emission of atomic oxygen, the OH Meinel bands, which appear as a continuum, and the atmospheric O2(O‐O) band of the
transition. This latter feature, which is not seen in ground observations of night airglow due to self absorption by atmospheric oxygen, was the single brightest emission of Earth’s night airglow seen in the present observations. The 300 kR measured intensity of this emission seen at the limb agrees closely with previous rocket measurements.
Structure of the magnetotail at 220 RE and its response to geomagnetic activity
Authors: Hones E. W. , Baker D. N. , Bame S. J. , Feldman W. C. , Gosling J. T. , McComas D. J. , Zwickl R. D. , Slavin J. A. , Smith E. J. , Tsurutani B. T.
Published: February 2008

Using plasma electron and magnetic field measurements from ISEE 3, 220 RE from earth, we find that the magnetotail at that distance is a coherent structure that evidently waves about through distances comparable to its own lateral scale size. For about one‐third of the time it was inside the magnetotail, ISEE 3 was in the plasma sheet. During quiet times the plasma sheet is apparently quite thin, but in response to geomagnetic activity it expands, becoming filled with hot plasma flowing tailward at speeds sometimes exceeding 1000 km/sec, and forces the magnetotail cross‐section itself to expand. The plasma sheet’s expansion is delayed typically by about 30 minutes from the onset of the associated geomagnetic activity (often a clearly identified isolated substorm). The magnetic field in the newly‐expanded plasma sheet usually exhibits a few‐minute steep northward excursion followed by a more prolonged (and often steep) southward excursion. We believe these to be the signatures of arrival of a plasmoid formed and released near the earth at the onset of the corresponding geomagnetic activity. The discreteness of these plasma releases through the magnetotail and their close association with onsets of geomagnetic activity at earth suggest that they are consequences of spontaneous release, probably by magnetic reconnection, of energy and plasma earlier stored in the magnetotail.
Effect of strain‐rate dependent yield strength on crater scaling relations
Authors: Gaffney E. S.
Published: February 2008

For materials whose strength is controlled by various creep processes, such as ice, the yield strength (Y) is often expressed in a power law relation to the strain rate (ε); Y ⧜ ⋵1/n, where n is a constant for some range of ⋵. It has been shown that, for strength‐dominated craters, the crater formation time is proportional to the crater radius R and to
. But the strain associated with crater formation is approximately fixed in the strength regime so the strain rate controlling crater formation will vary as
. The result of combining these two effects is that, in materials with strain‐rate dependent yield strengths, there will be a small increase in cratering efficiency (mass of ejecta/mass of explosive or impactor) as size increases in the strength‐dominated regime. Explosive cratering data indicate that 1.6<n<3.0 for centimeter‐ to meter‐scale craters. Use of conventional crater scaling relations will, therefore, underestimate the size of crater produced by an explosion in or impact into ice. Thus, ages inferred for surfaces on icy satellites may be too large.
Theoretical domain structure in multidomain magnetite particles
Authors: Argyle Kenneth S. , Dunlop David J.
Published: February 2008

Domain state energy calculations have been made for submicron magnetite cubes, based on a model consisting of planar domains of uniform magnetization separated by 180° domain walls (DWs). The magnetization within a DW is assumed to rotate uniformly, resulting in the appearance of magnetic poles of average density ±(2/π)Js on the particle faces bounding the DWs. Equilibrium domain structure configurations have been determined by minimization of the sum of the demagnetizing and wall energies. Domain structure transition sizes and particle remanences are reported for two‐domain and three‐domain magnetite cubes.
Energetic ion regimes in the deep geomagnetic tail: ISEE‐3
Authors: Cowley S. W. H. , Hynds R. J. , Richardson I. G. , Daly P. W. , Sanderson T. R. , Wenzel K.‐P. , Slavin J. A. , Tsurutani B. T.
Published: February 2008

During the period January 1 to March 30, 1983, the ISEE‐3 spacecraft was in a previously unexplored part of the distant geomagnetic tail (60‐220 RE). In two recent papers Slavin et al. (1983) have examined the gross morphology of the distant tail magnetic field, showing that a well‐ordered twin‐lobe structure is retained at these distances, while Bame et al. (1983) have reported plasma measurements for two 12‐hour intervals and have identified the plasma regions observed. In this paper, for the latter time intervals, the energetic ion (35 keV ‐ 1.6 MeV) and magnetic field measurements made by ISEE‐3 are reported and are related to the plasma measurements. The plasma sheet is found to be a region of enhanced fluxes of energetic ions, which are usually flowing unidirectionally tailward. These fluxes often extend outside the plasma sheet as identified in plasma data to form a plasma sheet boundary layer. A simple picture which accounts for these characteristics is given in which reconnection occurs at a neutral line lying Earthward of the spacecraft.
Mapping convection in the mantle
Authors: Tanimoto Toshiro , Anderson Don L.
Published: February 2008

Long‐period (100‐250 sec.) Love and Rayleigh waves are used to map heterogeneity and azimuthal anisotropy in the upper mantle. Spherical harmonic descriptions of anisotropy up to ℓ = m = 3 and 2θ are derived. Azimuthal anisotropy obtains values as high as 1½%. There is good correlation of fast Rayleigh wave directions with upper mantle return flow directions derived from kinematic considerations. This is consistent with the a‐axis of olivine being aligned in the flow direction. The main differences between the flow models and the Rayleigh wave azimuthal variation maps occur in the vicinity of hotspots. Hawaii, for example, appears to perturb the return flow. There is strong correlation of the geoid and surface wave velocity at ℓ = 4 and 5. Slow regions at this scale are associated with geoid highs and high heat flow, consistent with upwelling convective flow or with isostatically compensated regions of low density. The correlation of azimuthal anisotropy with upper mantle return flow directions, rather than with plate directions, suggests that part of the return flow is in the upper mantle and this, in turn, implies a low viscosity channel.
Composition measurements in the magnetotail between 60 RE and 240 RE
Authors: Ogilvie K. W. , Coplan M. A.
Published: February 2008

From 1 January, 1983 to 30 March, 1983 the ISEE‐3 spacecraft was in the region of the magnetotail of the earth at distances from 60 to 240 RE. The ion composition instrument aboard ISSE‐3 made ion composition and velocity measurements in two modes during this period. In the first mode the mass per charge (M/Q) range was 0.7 to 32 at velocities from 79 to 220 km s−1. The M/Q range of the second mode was 1.4 to 6.0 at velocities from 300 to 620 km s−1. Preliminary analysis of the data shows the magnetotail composition to have a significant solar wind‐like component, with bulk velocities generally in the 300‐600 km s−1 range.
Airborne observations of Arctic aerosol, IV: Optical properties of Arctic haze
Authors: Clarke A. D. , Charlson R. J. , Radke L. F.
Published: February 2008

Measurements of the horizontal and vertical distribution of aerosol light absorption and light scattering coefficients (at 550nm) for the Arctic aerosol show a high degree of correlation. Apparently originating from source areas at lower latitudes and present at various degrees of dilution, the haze observed was found to have a single scattering albedo in the range of 0.77 to 0.93 and a mean of ca. 0.86. Apart from sample periods with high seasalt concentrations at low altitudes or within ice crystal layers, the single scattering albedo values presented here are well below values characteristic of typical crustal aerosol but are similar to continental urban and rural values. These low values are consistent with arguments for mid‐latitude combustion source for this aerosol. The magnitude and variability in the observed optical parameters suggest near surface heating rates in the range of 0.01 to 0.1 degrees centigrade per day.
Transition stratigraphy and the problem of remanence lock‐in times in the Siwalik red beds
Authors: Tauxe L. , Badgley C.
Published: February 2008

The record of paleomagnetic polarity transitions can provide relative time information in the stratigraphic record on scales of hundreds to thousands of years. Transition stratigraphy is here used to determine the relative lock‐in times of several components of magnetization in the Siwalik red beds.
Bioturbation: Some effects on remanent magnetization acquisition
Authors: Ellwood Brooks B.
Published: February 2008

A 1 mm layer of magnetite powder has been sprinkled into a 3 cm deep, 1 meter long trench in high bioturbation rate tidal flat sediments, Sapelo Island, Georgia (USA). Periodic resampling and replicate remanent magnetization (RM) measurement indicates that within site RM directions and intensities stabilized between 20‐50 days after initial sampling. The RM mean after 50 days exhibits an inclination which is ˜20° less than the geomagnetic field inclination at the site and remains low through the Winter and Spring but then nearly disappears during the summer when bioturbation rates are extremely high, leaving a post‐depositional RM which is statistically indistinguishable from the earth's geomagnetic field inclination at the site. Since only very high bioturbation rates appear to produce a post‐depositional RM in this experiment, it is inferred that post‐depositional RM development in some low bioturbation rate natural sediments, e.g. locally in the deep‐sea, may be dominated by physical rather than biological depositional or post‐depositional processes.
Latitudinal and altitudinal variation of size distribution of stratospheric aerosols inferred from Sage aerosol extinction coefficient measurements at two wavelengths
Authors: Yue Glenn K. , Deepak Adarsh
Published: February 2008

A method of retrieving aerosol size distribution from the measured extinction of solar radiation at wavelengths 0.45 µm and 1.0 µm has recently been proposed. This method is utilized to obtain latitudinal and altitudinal variations of size distributions of stratospheric aerosols from the SAGE data for March 1979. Small particles are found in the lower stratosphere of the tropical region, and large particles are found at higher altitudes and latitudes in both hemispheres. Results of this study are consistent with the suggestion that the upper troposphere in tropical regions is a source of condensation nuclei in the stratosphere, and they become mature as they move to higher altitudes and latitudes.
Nightward ion flow in the Venus ionosphere: Implications of momentum balance
Authors: Elphic R. C. , Mayr H. G. , Theis R. F. , Brace L. H. , Miller K. L. , Knudsen W. C.
Published: February 2008

Using global empirical models of Venus ionospheric conditions, we solve for the plasma flow field consistent with the horizontal momentum equation in both viscid and inviscid forms. We find that plasma viscosity is negligible except at low altitudes and that the observed plasma flows are consistent with the inviscid solution above 300 km but are larger than the calculated flows at lower altitudes. This is probably due to downward momentum advection. The strong vertical shear in the calculated and observed flows just beyond the terminator may produce turbulence there, manifested as the observed transterminator waves in plasma density and magnetic field. We discuss the implications of ionospheric superrotation.