bluuebunny/crossref_metadata_2025 huggingface dataset:
A multiquadric‐biharmonic representation and approximation of disturbing potential
Authors: Hardy Rolland L. , Nelson Stuart A.
Published: February 2008

Properties of the potential are considered for applications in gravity, geomagnetic, and thermal field studies. It is found that classical theory is somewhat limited because of the common difficulty in evaluating potential within a material body containing the sources. The theory of a new type of representation of disturbing potential, a biharmonic form, is given which eliminates this difficulty. It is shown that multiquadric equations provide us with a physically valid numerical approximation of the formal integral representation. Error bounds are derived. The results of tests with real gravity anomalies are given, which compare classical methods with the new biharmonic form. In summary, the new approach eliminates the classical singularities associated with collocation of points of measurement (or prediction) and the sources of disturbing potential. It also improves computational efficiency.
Energy broadening due to space‐charge oscillations in high current electron beams
Authors: Katz I. , Jongeward G. A. , Parks D. E. , Reasoner David L. , Purvis Carolyn K.
Published: February 2008

During electron beam accelerator operation on Spacelab I, substantial fluxes of electrons were observed with energies greater than the initial beam energy. In this letter numerical calculations are performed for the emission of an unneutralized, one‐dimensional electron beam. These calculations show clearly that space charge oscillations, which are associated with the charge buildup on the emitter, strongly modify the beam and cause the returning beam particles to have a distribution of kinetic energies ranging from half to over twice the initial energy.
Time variations of the distant magnetotail
Authors: Fairfield D. H.
Published: February 2008

The likely dimensions of an extended earth magnetotail are investigated by considering various published polar cap and magnetotail observations in light of recent knowledge about magnetosphere behavior under different interplanetary magnetic field conditions. It is argued that the magnetotail is highly‐time dependent. During southward field conditions the tail probably attains its maximum radius but is subject to "breaking off" via substorm associated reconnection events which temporarily deplete the flux and reduce the radius. During northward interplanetary conditions more field lines are apt to close near the earth leaving considerably less flux to form any extended tail. Using estimates for both the amount of open polar cap flux and the tail flux at 60 Re, we argue that at 200 Re either the tail cross section is elongated in the equatorial plane or the average radius is not more than 25 Re.
Earthquakes in the “aseismic” regions of the western Pacific
Authors: Muirhead Ken , Adams R. D.
Published: February 2008

Operators of a deep ocean hydrophone array near Wake Island in the northwest Pacific Basin have located several previously unreported earthquakes within 20° of Wake Island in the "aseismic" interior of the Pacific plate, and have suggested high attenuation in the source region to explain why these events have not been reported by seismological agencies. The largest such earthquake occurred on 1983 June 29, in the Kiribati region; readings were submitted to the International Seismological Centre, but the earthquake was excluded from the final analysis because of doubt about its location and interfering arrivals from other earthquakes. Closer examination now provides a well‐determined seismological location and a magnitude of 4.7 (mb). Neither amplitudes nor frequency content of Australian records of the Kiribati earthquake support the existence of a region of abnormally high attenuation beneath the source. We suggest that the higher magnitudes reported from the hydrophone measurements result from the efficient coupling of energy from shallow intraplate earthquakes in the Pacific Basin into the Po/So waveguide.
Heat flux observations and the location of the transition region boundary of Giacobini‐Zinner
Authors: Fuselier S. A. , Feldman W. C. , Bame S. J. , Smith E. J. , Scarf F. L.
Published: February 2008

Electron heat flux observations and associated plasma phenomena upstream from comet Giacobini‐Zinner show many similarities to observations upstream from the Earth's magnetosheath. Two similarities are discussed. Heat flux events are used to compute the transition region boundary location. The computed subsolar standoff distance of 4×104 km is commensurate with a comet gas production rate, G, of 3×1028 molecules/s (mol/s), in accord with ground‐based determinations of G.
Detection of surface glow related to spacecraft glow phenomena
Authors: Langer W. D. , Cohen S. A. , Manos D. M. , Motley R. W. , Ono M. , Paul S. F. , Roberts D. , Selberg H.
Published: February 2008

We have developed a source of low energy neutral atoms and molecules by using a biased limiter to scrape‐off and reflect neutralized ions from a toroidal plasma. Beams of nitrogen and nitrogen‐oxygen mixtures with energies of 1 to 15 eV and fluxes ≳ 1014/cm²/s were directed onto target surfaces consisting of Z‐302 and Z‐306 paints. With the nitrogen beams we successfully detected a glow due to beam‐surface interactions. In addition, we observed a volume glow effect due to beam‐gas interactions which may play a role in spacecraft glow.
A model of comet P/Giacobini‐Zinner
Authors: Boice D. C. , Huebner W. F. , Keady J. J. , Schmidt H. U. , Wegmann R.
Published: February 2008

A computer model of Comet P/Giacobini‐Zinner is presented which contains photo‐processes, gas‐phase chemical kinetics, energy balance, multifluid hydrodynamics with a transition to free molecular flow, and solar wind interaction. Recently, the physics for electrons in the model has been improved by including electron impact ionization and dissociation and separately accounting for electron energetics. Electron heating and cooling mechanisms include photoprocesses, recombination processes, inelastic and elastic collisions with heavy molecules, and expansion cooling. The model incorporates an internally consistent interaction of the solar wind with the coma gas using the axisymmetric ideal fluid dynamic equations.

The nuclear size and composition have been chosen to make the calculations relevant to the 11 September 1985 International Cometary Explorer (ICE) encounter with Comet P/Giacobini‐Zinner. Model profiles of the temperature, velocity, and number density of the electrons are in good agreement with measurements along ICE's trajectory. These results indicate that the probe passed through a region of the coma at the onset of the plasma tail.
Optical spectrophotometry of comet P/Giacobini‐Zinner and emission profiles of H2O+
Authors: Strauss Michael A. , McCarthy Patrick J. , Spinrad Hyron
Published: February 2008

We have obtained two‐dimensional CCD spectrograms of Comet P/Giacobini‐Zinner (1984e) on five occasions between July and October 1985. We extracted spatial emission profiles of H2O+ at 6198 Å, the strongest ionic line in the visible spectrum. This emission line traces the extent of the ion, or plasma, tail. We placed the spectrograph slit approximately along the trajectory of the International Cometary Explorer (ICE) on 11 Sept 1985; the resulting H2O+ profile has a full‐width‐half‐maximum of ≈ 5700 km, about three times that of the plasma density profile measured by ICE, and has a full‐width‐zero‐intensity of ≈ 30,000 km, very similar to the ICE values. H2O production rates for the comet are derived and compared with those of Comet P/Halley (1982i).
The electron density and temperature in the tail of comet Giacobini‐Zinner
Authors: Marconi M. L. , Mendis D. A.
Published: February 2008

The electron density and temperature profiles along the tail axis of Comet Giacabini‐Zinner are calculated, using a multi‐fluid model of an H2O‐dominated atmosphere. The results obtained using this model, which was developed prior to ICE, are compared to the data from the mission and are found to be in satisfactory agreement with the ICE observations.
nonlinear mixing in the ionosphere
Authors: Ganguly Suman , Gordon W. E.
Published: February 2008

When the ionosphere is illuminated with two strong HF signals, nonlinear mixing processes can take place near the region of reflection. The first direct experimental evidence of such processes occurring in ionospheric plasma are presented in this paper. The experiments were performed at Arecibo, where the HF ionospheric modifier was split to operate as two pure isolated and independent pumps over the frequency range of 3‐8 MHz and the frequency difference between the two pumps was varied between a fraction of a Hz and several kHz. The purity of the trans‐ mitted signals was always ensured. Strong nonlinear effects were observed when the frequency difference was several Hz. Specifically, the HF signal from the ionosphere contained sidebands which were separated by multiples of the difference (Δf) between the two pumping frequencies. The first sidebands were typically 20‐40 db below the pump signal. The strengths of the first sidebands increased, when the difference (Δf) between the two pumping frequencies decreased. Below about 5‐10 Hz, the power in the first sidebands varied almost in Δf−n fashion, with n between 1 and 2. The power in the sidebands was also a strong nonlinear function of the incident pump field strength, showing the presence of a threshold. It is suggested that studies of such nonlinear mixing processes would be valuable both for diagnostic and practical usage of ionospheric plasma.
STS‐9 shuttle glow: Ram angle effect and absolute intensities
Authors: Swenson G. R. , Mende S. B. , Clifton K. S.
Published: February 2008

Visible imagery from Space Shuttle mission STS‐9 (Spacelab 1) has been analysed for the ram angle effect and the absolute intensity of glow. The data are compared with earlier measurements and the anomalous high intensities at large ram angles are confirmed. Absolute intensities of the ram glow on the shuttle tile, at 6563 Å, are observed to be ˜20 times more intense than those measured on the AE‐E spacecraft. Implications of these observations for an existing theory of glow involving NO2 are presented.
Radial diffusion and ion partitioning in the IO torus
Authors: Cheng Andrew F.
Published: February 2008

A model is presented for radial diffusion and charge state partitioning of sulfur and oxygen ions in the Io torus, including effects of electron impact and charge exchange. When applied to Voyager 1 radial profiles of total ion flux tube content, the model shows that the ion residence time in the torus, τD, as defined in spectroscopic studies of ion partitioning, is related to the radial diffusion coefficient, DLL, at L = 7 by τD ≈ 8/DLL(7). This result appears to bring spectroscopic estimates of the ion residence time (τ D ≳ 60 to 100 days) into reasonable agreement with estimates of DLL from magnetospheric diffusion studies, DLL ≈ 10−6s−1.
Study of tidal periodicities using a Transatlantic telecommunications cable
Authors: Thomson D. J. , Lanzerotti L. J. , Medford L. V. , Maclennan C. G. , Meloni A. , Gregori G. P.
Published: February 2008

We report the results of determinations of tidal periods from spectral analysis of the voltage induced across an unpowered length of the TAT‐7 telecommunications cable in the North Atlantic Ocean over an approximately 19 day interval. Particularly prominent spectral components are observed at several frequencies, including those identified as corresponding to the diurnal declination luni‐solar (K1), semi‐diurnal principal solar (S2), semidiurnal principal lunar (M2), and monthly lunar (Mm), components. In addition, a large amplitude spectral component of high statistical significance was observed at a frequency of 3.0051 cpd, approximately one‐third the sidereal day. This component does not appear to be related to the solar component S3 and possibly corresponds to a declination luni‐solar K3 frequency, although the amplitude is very much larger than that which might be expected. Other common lunar tides appear to be a minor component of the data. Such cable data can be used for studies and refinement on a global scale of large‐scale tidal (ocean and ionosphere) models.
Tectonic Setting and Source Parameters of the September 19, 1985 Michoacan, Mexico Earthquake
Authors: Eissler Holly , Astiz Luciana , Kanamori Hiroo
Published: February 2008

Analysis of body waves and long‐period surface waves from the September 1985 earthquake in coastal Michoacan, Mexico shows that the event was an interplate subduction event with a low dip angle fault plane (δ=9°) striking parallel to the Mid‐America trench (ϕ=288°) and a small component of left lateral motion (λ=72°) with a point source depth of 17 km, and a seismic moment in excess of 1 × 1028 dyn cm. The earthquake was a multiple event, with a second source of identical moment, fault geometry, and depth occurring approximately 26 s after the first. Directivity in the body wave time function indicates that the second event occurred roughly 100 km to the southeast of the first. This suggests that the earthquake first broke the northern portion of the Michoacan gap, propagated with low moment release through the rupture zone of the 1981 Playa Azul earthquake, and then broke the remaining asperity in the southern section of the gap. The seismic moment determined from Rayleigh and Love waves is between 1.0 ‐ 1.7 × 1028 dyn cm (MW = 7.9 ‐ 8.1), the largest moment determined to date for a Mexico subduction earthquake. Comparison of seismograms at Pasadena with records of other large Mexico events shows that the Michoacan earthquake is basically the same size as the 1932 Jalisco, Mexico earthquake, and clearly larger than other significant events in Mexico since 1932. The seismic moment and the time since the last large earth‐quake in Michoacan (in 1911) fit an empirical relation between moment and recurrence time found for the Guerrero‐Oaxaca region of the subduction zone. The large aftershock on September 21 (Ms=7.5) has the same geometry as the mainshock, a somewhat larger source depth (22 km), a simple time function, and a seismic moment between 2.9 ‐ 4.7 × 1027 dyn cm (Mw = 7.6 ‐ 7.7).
The September 19, 1985 Michoacan Earthquake: Aftershock acceleration data recorded by a temporary installation of strong motion instruments
Authors: Munguía Luis , Simila Gerry W. , McNally Karen C. , Thompson Howard
Published: February 2008

We describe acceleration signals recorded for nine aftershocks of the September 19, 1985 Michoacan earthquake. To obtain this data set, three A‐700 Teledyne‐Geotech digital strong‐motion instruments were operated temporarily at two sites on the José María Morelos (La Villita) Dam, and at a site located at about 12 km to the west of the town of Zihuatanejo. Peak horizontal accelerations of 0.005 g to 0.031 g were recorded at epicentral distances between 10 and 75 km, for earthquakes with magnitude (mb) between 4.5 and 5.3. It was observed that the peak accelerations recorded at a site on the embankment of the dam (near the crest ) are approximately three times those recorded on the abutment bedrock portion of the dam. Although these sites were spatially separated by no more than 300 m, differences among their records are also significant. Waveforms recorded at the embankment site look more complex than those from the abutment site. This fact, as well as the higher peak accelerations on the embankment, provides evidence of a strong influence of the structure of the dam on the ground motion at the embankment site.
Structural damage in Mexico City
Authors: Hall John F. , Beck James L.
Published: February 2008

This paper describes the structural damage in Mexico City caused by the September 19, 1985 earthquake. Photographs which illustrate various features of structural behavior are included. One explanation is presented as to why buildings with fundamental periods of elastic vibration considerably below the predominant two‐second period of the ground motion were most vulnerable to damage.
Source mechanism of the September 19, 1985 Michoacan Earthquake and its implications
Authors: Priestley Keith F. , Masters T. Guy
Published: February 2008

Moment tensor inversion of low frequency teleseismic data for the September 19, 1985 Michoacan, Mexico earthquake gave an average strike 298°, slip 268°, and seismic moment 10.3×1027 dyne‐cm. Low frequency body waves clearly show the complex nature of this event. Cross‐correlation of the September 19 P‐wave with that of the smaller, and colocated October 25, 1981 Playa Azul earthquake, show that the Michoacan earthquake consisted of two subevents separated in time by 25 s, and located approximately 30 km northwest and 40 km southeast respectively, of the Playa Azul epicenter. Body wave inversion of the first subevent gave strike 298°, slip 266°, and seismic moment 3.0×1027 dyne‐cm. The second subevent had a comparable seismic moment. The cumulative moment for large earthquakes occurring along the Michoacan‐northwest Guerrero coast indicate that seismic displacement along this segment of the Mexican subduction zone is similar to that occurring on other portions, indicating that the "former" Michoacan gap was not anomalously aseismic.
Heliocentric radius of the cosmic ray modulation boundary
Authors: Randall B. A. , Van Allen J. A.
Published: February 2008

We have made a semi‐empirical analysis of our extensive body of observed cosmic ray intensity data from Pioneers 10 and 11 and related spectral information from other authors in order to infer the radius R of the modulation region surrounding the sun. During the period 1972‐1985 the inferred values of R vary with time systematically and in a manner generally similar to that of sunspot numbers. The range of values of R is from 42 AU at the time of minimum solar activity (∼ 1976) to 88 AU about 1.5 yr following the time of maximum solar activity (∼ 1980). A specific, testable prediction is that Pioneer 10 will reach the modulation boundary in 1988 and will remain in its vicinity for several years thereafter.
Plasma waves associated with the first AMPTE magnetotail barium release
Authors: Gurnett D. A. , Anderson R. R. , Bernhardt P. A. , Lühr H. , Haerendel G. , Bauer O. H. , Koons H. C. , Holzworth R. H.
Published: February 2008

Plasma waves observed during the March 21, 1985, AMPTE magnetotail barium release are described. Electron plasma oscillations provided local measurements of the plasma density during both the expansion and decay phases. Immediately after the explosion the electron density reached a peak of about 4 × 105 cm−3, and then started decreasing approximately as t−2.4 as the cloud expanded. About 6 minutes after the explosion the electron density suddenly began to increase, reached a secondary peak of about 2.4 × 10² cm−3, and then slowly decayed down to the pre‐event level over a period of about 15 minutes. The density increase is believed to be caused by the collapse of the ion cloud into the diamagnetic cavity created by the initial expansion. The plasma wave intensities observed during the entire event were quite low. In the diamagnetic cavity electrostatic emissions were observed near the barium ion plasma frequency, and in another band at lower frequencies. A broadband burst of electrostatic noise was also observed at the boundary of the diamagnetic cavity. Except for electron plasma oscillations no significant wave activity was observed outside of the diamagnetic cavity.
Heavy ozone in the stratosphere
Authors: Bates David R.
Published: February 2008

On taking account of the symmetry numbers involved it is found that the rate coefficient of the ter‐molecular association process giving heavy ozone is greater than that of the corresponding process giving regular ozone. It is suggested that this is the explanation of the 50O3 enhancement observed in the stratosphere.
Heat flow measurements on a hydrothermally‐active, slow‐spreading ridge: The Escanaba Trough
Authors: Abbott Dallas H. , Morton Janet L. , Holmes Mark L.
Published: February 2008

Maximum heat flow measurements at three locations in the sediment‐filled Escanaba Trough of the Gorda ridge exceed 1200 mW/m². At other ridge crests with thick sediment cover, heat flow values of this magnitude are accompanied by high temperature hydrothermal vent activity and massive sulfide deposition. A dredge haul from the southernmost high heat flow location recovered pyrrhotite, thereby confirming the presence of recent high temperature venting.
The Msissi Norite revisited: K/Ar dating, petrography and paleomagnetism
Authors: Salmon E. , Montigny R. , Edel J. B. , Pique A. , Thuizat R. , Westphal M.
Published: February 2008

The "Msissi norite" in Morocco (30.93°N, 4.71°W) from where one of the paleomagnetic reference pole for Africa in Devonian times has been derived, has been revisited and dated. Petrological examination shows that the rock is an alkaline gabbro (teschenite). K‐Ar analyses on fresh biotite yield a 136‐139 Ma age, which infirms the supposed Devonian age. The paleomagnetic study displays several distinct magnetic components.
Evidence for the presence of the 802.7‐CM−1 band Q branch of HO2NO2 in high resolution solar absorption spectra of the stratosphere
Authors: Rinsland C. P. , Zander R. , Farmer C. B. , Norton R. H. , Brown L. R. , Russell J. M. , Park J. H.
Published: February 2008

Stratospheric solar absorption spectra recorded at ∼0.01 cm−1resolution by the ATMOS (Atmospheric Trace Molecule Spectroscopy) Fourier transform spectrometer during the Spacelab 3 Shuttle mission (4/30‐5/6/85) show a weak absorption feature covering ∼802.5‐803.3 cm−1. We identify this feature as the unresolved Q branch of the 802.7‐cm−1 band of HO2NO2 and report profiles for 31°N and 47°S.
Effects of anomalous transport on the potentials of discrete auroral arcs
Authors: Smith Robert A.
Published: February 2008

The evolution of U‐shaped double layers in discrete auroral arcs occurs much faster than the global current in the arc flux tube can be redistributed. For asymptotic stality of the arc on MHD time scales, this implies that local transport mechanisms are required to charge the nearly field‐aligned flanks of the equipotential structure over an extended region along the magnetic field. The diversion of the uniform upstream current provides a constraint which limits the double‐layer potential.
Plasma waves in the shock interaction regions at comet Giacobini‐Zinner
Authors: Kennel C. F. , Coroniti F. V. , Scarf F. L. , Tsurutani B. T. , Smith E. J. , Bame S. J. , Gosling J. T.
Published: February 2008

Basic uncertainties about the nature of the comet‐solar wind interaction have existed for decades, and even gross features of the interaction phenomena were poorly understood on theoretical grounds alone. The first discussions of measurements from the encounter of ICE (International Cometary Explorer) with Comet Giacobini‐Zinner did not provide immediate clarification of these issues. Here we analyze the nature of the interaction by examining the detailed evolution of the plasma wave spectra across the interaction region. It is shown that the cometary spectra are very similar to those detected at certain classes of interplanetary shocks and terrestrial bow shocks.
On the Initial motion of artificial comets in the AMPTE releases
Authors: Papadopoulos K. , Lui A. T. Y.
Published: February 2008

The early time (t < 300 s) interaction of the Ba+ cloud with the solar wind during the AMPTE comet release is examined, with an emphasis on the issue of the Ba+ ion magnetization. It is shown that the observed magnetic field profile is consistent with the Ba+ ions being magnetized, in the sense that the cloud radius , is the Ba+ gyroradius. As a consequence, any momentum coupling force F between the Ba+ cloud and the solar wind in their relative streaming direction will produce an acceleration drift in a direction consistent with the observations. The drift will cease when the cloud expands to the extent that the magnetic field inside the cloud is reduced to satisfy . The implications of the model to observables of the interaction are discussed.
El Chichon and “mystery cloud” aerosols between 30 and 55 km: Global observations from the SME visible spectrometer
Authors: Clancy R. Todd
Published: February 2008

Visible limb radiances measured by the Solar Mesophere Explorer (SME) are used to obtain volume scattering ratios for aerosol loading in the 30‐55 km altitude range of the stratosphere. Global maps of these ratios are presented for the period January, 1982 to August, 1984. Significant aerosol scattering from the "mystery cloud" and El Chichon aerosol layers are found above 30 km. A timescale of approximately 2 months between the appearance of the aerosol at 30.5 km and at 37.5 km is consistent with vertical transport of aerosol or vapor by eddy diffusion above 30 km. An anticorrelation exists between aerosol scattering and stratospheric temperatures. Periods of lower stratospheric temperatures may account for the formation of aerosol between 40 and 55 km altitude.
Telluric currents and magnetic anomalies
Authors: Cull J. P. , Tucker D. H.
Published: February 2008

Current densities of 2.5*10−4 amp/m² can be generated by constant groundwater migration in artesian aquifers. These DC currents are sufficient to generate magnetic anomalies exceeding 200 nT in both the Menindee Trough (Australia) and the Karoo Basin (South Africa). Telluric currents associated with ionospheric activity can be detected by variations in magnetic induction but constant offsets associated with streaming potentials and geochemical activity (SP anomalies) are obscured by noise. Consequently some regional magnetic anomalies may be wrongly attributed to variations in magnetic susceptiblity with residuals explained by remanence.
Possible detection of the Earth's free‐core nutation
Authors: Robertson D. S. , Carter W. E. , Wahr John M.
Published: February 2008

Theoretical studies indicate that interactions between the Earth's mantle and fluid core could produce a near 460‐day, retrograde circular component of the nutation, often called the free‐core nutation (FCN). Until now this phenomenon has never been observed. We use the 5.5 years of VLBI observations primarily collected under project IRIS to search for evidence of the FCN. The observations are consistent with an irregular excitation process, and a model which assumes a step excitation in the FCN amplitude to about 2.0 milliseconds of arc in late 1985 fits the data well. Theoretical analysis appears to rule out the strong Mexican earthquake of September 19, 1985, as a cause of the excitation.
Aircraft observations of large raindrops in warm, shallow, convective clouds
Authors: Beard Kenneth V. , Johnson David B. , Baumgardner D.
Published: February 2008

Raindrop size distributions have been obtained using airborne optical array probes during the 1985 Joint Hawaiian Warm Rain Project near Hilo. Drops often extended to 4 or 5 mm diameter, and on one occasion even reached 8 mm—much larger than had been previously reported. Large raindrops were detected frequently enough to indicate that they may be a regular feature of tropic clouds which are rather shallow but convectively active. The preliminary analysis of the data, involving some simple cloud physics calculations, indicates that the conditions in these clouds are well suited for the growth and survival of large raindrops. The presence of large raindrops suggests that a number of wide‐spread views on the formation and evolution of warm rain should be altered, and that earlier data obtained in the orographic clouds of Hawaii should not be extrapolated uncritically to all types of warm rain.
Effective magnetic susceptibility of the oceanic upper mantle derived from MAGSAT data
Authors: Arkani‐Hamed Jafar , Strangway David W.
Published: February 2008

Passive ocean‐continent boundaries have little magnetic signatures at MAGSAT altitude, ∼400 km, whereas subducting oceanic lithosphere has well defined magnetic anomalies over some of the subduction zones. Based on this observation, and a thermal evolution model of the oceanic lithosphere subducted along the Kuril‐Kamchatka trench, we determined an effective magnetic susceptibility of 0.0085 SI for the upper ∼35 km of the oceanic upper mantle.
Test of the lower mantle slab penetration hypothesis using broadband S waves
Authors: Beck Susan L. , Lay Thorne
Published: February 2008

Broadband S and ScS displacement pulses from deep‐focus earthquakes in the Sea of Okhotsk, recorded at analog and digital stations in North America and Europe, show complexities produced by velocity heterogeneity in the lower mantle. The slab beneath the Sea of Okhotsk strikes N40°E, while the stations used in this study range from N40°W to N70°E, allowing a test of the hypothesis that multipathing in a lower mantle slab extension gives rise to the waveform complexities. Comparisons of the S and ScS displacement pulses at a given station indicate that in many cases the direct S pulses have a broader, more complex waveform than the ScS pulses. We parameterized the waveform complexity by the energy temporal centroid difference (CS‐CScS) between the S and ScS pulses. The largest CS‐CScS anomalies are observed along the strike of the slab. There is also a correlation between the CS‐CScS values and ScS‐S travel time residuals for stations along the strike of the slab and no correlation for off‐strike azimuths. However, CS‐CScS anomalies are observed over the entire azimuth range, including azimuths to the southwestern U.S., for which the raypaths should quickly exit any deep slab structure. These data suggest that lateral velocity heterogeneities both near the source (possibly due to slab penetration) and deep in the mantle near the S wave turning points contribute to the S and ScS complexity.
First analyses of broadband records on the Geoscope Network: Potential for detailed studies of mantle discontinuities
Authors: Souriau Annie
Published: February 2008

Examples of the first analyses of broadband GEOSCOPE data at station SSB (France) show that these data will make possible a detailed study of the deep mantle discontinuities.

Analysis of the P‐coda of earthquakes using specific methods suggests the existence of P to S conversions at 670 km depth beneath SSB for earthquakes with northern to eastern azimuths; a comparison with results from the NARS and Grafenberg arrays indicate that the 670 km discontinuity beneath western Europe is highly heterogeneous or horizontally discontinuous. A frequency analysis reveals that the relevant discontinuity is not very sharp ( ∽ 20 to 70 km thick). Besides, a sharp ( < 5 km thick) discontinuity at 900 km depth is observed beneath the Mid‐Atlantic Ridge from P reflections, giving PP precursors, for the strong March 1985 Chilean earthquake, but no 670 km discontinuity seems to be present beneath the Ridge.
Excess heating over the equatorial latitudes during storm sudden commencement
Authors: Gupta Ranjan , Desai J. N. , Raghavarao R. , Sekar R. , Sridharan R. , Narayanan R.
Published: February 2008

Temperatures of the equatorial thermosphere were obtained from the rocket released vapour clouds during (i) geomagnetically quiet and (ii) just after (<2 hrs) a sudden commencement. These measurements of thermospheric temperatures at different altitudes during sudden commencement are the first of their kind. The results reveal larger temperatures (>400 ‐ 500°K) than that expected by the Jacchia 77 model during disturbed periods, while the quite day measurements agree well with the model predictions. The possible sources of energy that account for the excess temperatures are discussed in the context of the present measurements.
Evidence for a large bulk ion conic heating region
Authors: Temerin M.
Published: February 2008

The ion bowl distribution, a type of ion conic with a low energy ion cutoff and field‐aligned low energy ions, can be explained by purely perpendicular heating of ions on auroral magnetic field lines. The ion bowl distribution provides evidence that there exists a bulk ion heating mechanism, as opposed to a mechanism that effects only the tail of the ion distribution, and that this heating mechanism acts along a large portion of the magnetic field line.
Comment on the Pioneer Venus Orbiter Event of February 11, 1982: of cometary or solar origin?
Authors: Intriligator Devrie S.
Published: February 2008

Analysis of Pioneer Venus Orbiter (PVO) and ISEE plasma and magnetic field observations associated with the PVO February 10‐11, 1982 events strongly supports the solar origin of the events and not the cometary origin suggested by Russell et al. (1985b). The observation of the field fluctuations and helium enhancements at both Venus and Earth strongly supports the solar origin of the events. Helium enhancements are associated with solar events and not with cometary events. The sequence of the events — the sheath, the magnetic cloud, and the trailing filament (with its increase in magnetic field magnitude) — is entirely consistent with the solar origin of the events. Three additional observations strongly argue for a solar not a cometary origin of these events: in contrast to the observations at comet Giacobini‐Zinner, no significant plasma wave activity was recorded at PVO at the time Russell et al. claim the cometary bow shock was crossed, thus arguing against the presence of a cometary bow shock; the Venera 13 and 14 magnetic field observations at Venus show that the solar wind was disturbed at this time, which is consistent with the solar origin of these events; and a Forbush decrease was recorded at Earth within a day after the observation of the events at ISEE‐3, which also strongly argues for a solar wind and not a cometary origin of the events. We believe the available observations argue for a solar and not a cometary origin of these events.
Extending the linear regime of the seismic waveform inversion problem
Authors: Shaw Peter R.
Published: February 2008

A method is presented for expanding the “locally linear” regime in the iterative seismic waveform inverse problem. This formulation increases the class of starting models that successfully converge on a solution.
Off‐line acquisition of crustal reflection and refraction data
Authors: Milkereit B. , Bittner R. , Meissner R.
Published: February 2008

A piggy‐back seismic reflection survey was carried out in 1984 as part of the DEKORP 2‐S profile. The signal from explosive‐sources was digitally recorded on 120 channels. The objectives were: a) To record crustal reflections at a wide range of incidence angles (5‐85 km offset) b) To provide 3‐D control of deep crustal reflectors seen on the main profile.

An important consideration throughout the fieldwork was to avoid interference with the main reflection survey. This experiment showed that explosive charges as small as 5‐90 kg may provide sufficient energy for observations from the steep‐angle to the wide‐angle range. The off‐line position of the receivers allowed the reconstruction of steep‐angle reflection profiles parallel and perpendicular to the main reflection line. A strong diffraction cluster on the main line could be correlated laterally, and indications about the diffractors' shape could be obtained.
Geomagnetic reversals from impacts on the Earth
Authors: Muller Richard A. , Morris Donald E.
Published: February 2008

The impact of a large extraterrestrial object on the Earth can produce a geomagnetic reversal through the following mechanism: dust from the impact crater and soot from fires trigger a climate change and the beginning of a little ice age. The redistribution of water near the equator to ice at high latitudes alters the rotation rate of the crust and mantle of the Earth. If the sea‐level change is sufficiently large (>10 meters) and rapid (in a few hundred years), then the velocity shear in the liquid core disrupts the convective cells that drive the dynamo. The new convective cells that subsequently form distort and tangle the previous field, reducing the dipole component near to zero while increasing the energy in multipole components. Eventually a dipole is rebuilt by dynamo action, and the event is seen either as a geomagnetic reversal or as an excursion. Sudden climate changes from other causes such as volcanic eruptions could also trigger reversals. This mechanism may not be the sole cause of geomagnetic reversals, but it can account for the rapid drop of the dipole component preceding a reversal, the predominance of multipole components during a transition, the associations of microtektites, temperature drops and extinctions with reversals, and the possible correlation between peaks in the geomagnetic reversal rate and the times of mass extinctions. The model may also account for the long‐term changes in the average rate of reversals. We make several testable predictions.
Further interpretation of satellite measurements of Antarctic total ozone
Authors: Stolarski Richard S. , Schoeberl Mark R.
Published: February 2008

Both dynamical and chemical mechanisms have been advanced to explain the decrease in total ozone in the Antarctic spring. Further analysis of satellite measurements show that during any one year the September decline in total ozone near the South Pole is compensated by an increase at mid‐latitudes. The total ozone amount from 44° S to the pole remains almost unchanged from August through November even though both the polar and mid‐latitude values reach extremes during this period. These observations suggest that the variations within the spring season in south polar total ozone are governed by dynamical redistribution rather than chemical processes.
The vertical ozone distribution in the Antarctic ozone minimum measured by SBUV
Authors: McPeters R. D. , Hudson R. D. , Bhartia P. K. , Taylor S. L.
Published: February 2008

The ozone profiles measured by SBUV in the region of the antarctic ozone minimum are in error as archived for altitudes below the 7 mb level in the atmosphere because of the lack of a reasonable climatology to use for the initial guess profile. We have examined the ozone profile error in this region and have shown that use of a reasonable climatology in this unusual region results in ozone profiles that agree substantially better with the balloon observations available from the Syowa station. The corrected profiles show that by 1984 there was 35% less ozone in the 15 to 30 km region than in 1979, and 14% less even in the 40 to 50 km region.
Antarctic O3: Chemical mechanisms for the spring decrease
Authors: McElroy Michael B. , Salawitch Ross J. , Wofsy Steven C.
Published: February 2008

Chemical explanations for the spring decline of Antarctic O3 involve reactions of ClO or interactions between BrO and ClO. Reaction schemes involving Br radicals have the highest efficiency for removal of O3. The chemical mechanisms require low levels of NOx. Recent cooling of the stratosphere may have triggered formation of HNO3 monohydrate, removing NOx and setting the stage for enhanced loss of ozone over Antarctica.
Radiative heating due to stratospheric aerosols over Antarctica
Authors: Shi Guang‐Yu , Wang Wei‐Chyung , Ko Malcolm K. W. , Tanaka Masayuki
Published: February 2008

The 1982 balloon measurements of temperature, ozone, humidity, and ground‐based measurements of turbidity at Syowa station (69°S, 39°E) in Antarctica are used to study the solar and thermal radiative effects due to gases and aerosols. Our calculations indicated that, with the observed temperature, the thermal radiative cooling due to CO2 and O3 emissions yielded a net radiative cooling in the lower stratosphere throughout the year if the effects of aerosols were excluded. However, the results are very sensitive to the reported ambient temperature. Contribution by aerosols to solar heating was found to be smaller than that due to O3 absorption. The aerosols played a more important role in the long‐wave radiation by providing a thermal heating from March to September. During the winter months the thermal heating almost compensated for the cooling due to CO2 and O3 emissions resulting in a near radiative equilibrium state. This sets the stage for a net radiative warming in spring from absorption of solar energy, which may provide energy for an upwelling motion responsible for the ozone hole. Both the temperature distribution and aerosol properties should be studied in more detail in connection with the dynamical thesis for the O3 hole and its interannual variations.
Reactions of chlorine nitrate with HCl and H2O
Authors: Hatakeyama Shiro , Leu Ming‐Taun
Published: February 2008

The kinetics of the reactions of chlorine nitrate with HCl and H2O have been investigated using a static photolysis/Fourier transform infrared spectrophotometer apparatus. Upper limits for the rate constants for the homogeneous gas‐phase reactions of ClONO2 + HCl (1) and ClONO2 + H2O (2) were estimated to be <8.4 × 10−21 and <3.4 × 10−21 cm³ molec−1 s−1 respectively, at 296 ± 2 K. The yields of HNO3 were 1.05 ± 0.09 and 0.86 ± 0.08, respectively. No synergistic effect between H2O and HCl was observed. The kinetic behavior of reaction (2) was well described by simple first‐order kinetics while the behavior of reaction (1) was found to be well described in terms of the Langmuir adsorption isotherm.
Magnetospheric particle injection and the upstream ion event of September 5, 1984
Authors: Krimigis S. M. , Sibeck D. G. , McEntire R. W.
Published: February 2008

Energetic particle data from the AMPTE Charge Composition Explorer (CCE) spacecraft in the outer dayside magnetosphere are examined during the period of an upstream ion event observed by the AMPTE Ion Release Module (IRM) spacecraft on September 5, 1984 [Moebius et al., this issue]. The CCE data reveal the following: (a) an ion enhancement was observed at ∼0040 UT in near coincidence with a substorm onset at ∼0035 UT, approximately 15 minutes prior to the onset of the event upstream of the shock; (b) ions of both solar wind (He ++, Fe‐group) and ionospheric (O+) origin over a broad energy range (∼20 keV to > 1350 keV) were injected at substorm onset; (c) the time evolution of the H+, He++, and O+ pitch angle distributions markedly differed, with O+ exhibiting mostly enhancements at off‐90° angles for the first hour after injection; (d) an enhancement in the Fe‐group ions inside the magnetosphere at L ∼ 6.4 occurred simultaneously with the appearance of an O+ burst upstream of the shock. The CCE observations, taken together with the simultaneously observed IRM ion event, suggest that a plausible explanation for the appearance of upstream ions is leakage from the magnetosphere into the upstream region, rather than the alternate explanation which requires in‐situ acceleration of solar wind ions via the Fermi mechanism.
Changes in aerosol content and temperature in the Antarctic spring stratosphere: Lidar measurement at Syowa Station (69°00′S, 39°35′E) in 1983, 1984 and 1985
Authors: Iwasaka Y. , Ono T. , Nonura A.
Published: February 2008

Measurements on stratospheric aerosols at Syowa Station (69°00′S, 39°35′E) in 1983, 1984 and 1985 are described. The year‐to‐year changes in aerosol content were influenced by volcanic eruption of Mt. El Chichon (spring 1982, Mexico) and variations of stratospheric temperature. The aerosol load in winter of 1983 was about five times larger than the load of 1985. The particle content of spring 1985 was larger than that of spring 1983 even though the effect of the volcanic eruption was more severe in 1983. This may be a result of the decrease in average stratospheric temperature in spring. If heterogeneous reactions including the particles are indeed important for Antarctic ozone depletion, the rate of ozone depletion from heterogeneous reactions in the Antarctic spring must have increased from 1983 to 1985.
Evidence for S(IV) compounds other than dissolved SO2 in precipitation
Authors: Chapman E. G.
Published: February 2008

Preliminary results from a study characterizing S(IV) compounds in wintertime precipitation samples indicate that bisulfite ion is not the primary form of S(IV), as previously believed. By employing a differencing technique that permits estimation of both SO2 · aq and non‐SO2 · aq compound concentrations, it was found that, on an average, more than 60% of the total S(IV) is present in a form other than dissolved SO2. Formaldehyde analyses on selected samples suggest that the most likely form of the S(IV) is hydroxymethanesulfonate, although other aldehyde‐S(IV) adducts may also be present. The non‐SO2‐compounds represented a significant portion of the total sulfur concentrations present in the samples analyzed, with contributions ranging from 1.2 to 27%. Because of the stability and oxidation resistance of these S(IV) compounds, sulfur deposition estimates that are based solely on sulfate measurements are undoubtedly low, especially for wintertime events. The study underscores the importance of S(IV) compounds in atmospheric scavenging processes.
Secondary remanent magnetization of pelagic clay in the South Pacific: Application of thermal demagnetization
Authors: Yamazaki Toshitsugu
Published: February 2008

Previous paleomagnetic studies have revealed that pre‐Quaternary pelagic clay with neither siliceous nor calcareous fossils has unstable remanent magnetization, and that alternating field (AF) demagnetization is not effective to remove the secondary magnetization. This study applied thermal demagnetization on pelagic clay from the South Pacific, and recovered characteristic directions. The observed paleolatitudes agree with those from plate tectonic analysis, which proves that the thermal demagnetization worked well. The magnetic overprint is estimated to be viscous remanent magnetization (VRM) from VRM acquisition experiment. A hypothesis is proposed that the magnitude of the VRM of pelagic clay has been controlled by the grain size of magnetic minerals of eolian origin, which has been subjected to the intensity of the global atmospheric circulation. This can explain the Late‐Pliocene unstable‐to‐stable transition of the remanence, which has been observed widely in the Pacific.
Evidence of a lower mantle shear velocity discontinuity in S and sS phases
Authors: Lay Thorne
Published: February 2008

Teleseismic recordings of direct S and sS body wave phases, and their core‐reflected counterparts ScS and sScS, from intermediate and deep focus earthquakes are used to analyze the lowermost mantle shear velocity structure beneath Alaska. A model with a 2.75% shear velocity increase 280 km above the core‐mantle boundary accurately matches waveform complexities in both the S and sS wavetrains. Variations in source depth produce systematic shifts in the timing of the triplication arrivals between the S and sS travel time branches that are readily observed in long‐period WWSSN tangential component recordings. The systematic range‐ and depth‐dependence of the observed shifts are well‐predicted by the discontinuity model, and preclude explanations of the waveform complexity as resulting from multiple ruptures at the source, receiver reverberations, or near‐source scattering from slab structure.
Aspherical structure of the core‐mantle boundary from PKP travel times
Authors: Creager Kenneth C. , Jordan Thomas H.
Published: February 2008

Maps of aspherical structure in the vicinity of the core‐mantle boundary have been constructed from a tomographic analysis of P′DF and P′AB travel times in the distance range 150°‐180°. These maps reveal long‐wavelength features not previously detected by mantle tomography. The peak‐to‐peak amplitude of these features is on the order of 1 s in vertical travel time, too large to be explained by conventional thermal boundary layer models or dynamically supported topography on the core‐mantle boundary. We hypothesize the existence of one or more chemical boundary layers whose large‐scale accumulations on the surface of the core may in some ways be analogous to continents at the earth's surface.