bluuebunny/crossref_metadata_2025 huggingface dataset:
The potential of soils as a sink of chlorofluorocarbons and other man‐made chlorocarbons
Authors: Khalil M. A. K. , Rasmussen R. A.
Published: February 2008

Based on our field experiments, we considered whether CCl4, CH3CCl3, CCl3F (F‐11), CCl2F2 (F‐12) and C2Cl3F3 (F‐113) are removed by soils at the earth's surface. We found that the rate of removal is greatest for CCl4, moderate for CH3CCl3 and F‐11, slight for F‐12 and not significant for F‐113. By removing these gases from the atmosphere, before they can reach the stratosphere, such processes may prevent some depletion of the ozone layer from the continued releases of these man‐made chlorocarbons. Because of the enormous variability, credible estimates of the global magnitude of the soil sink cannot be obtained from the present data.
On the satellite retrieval of aerosol optical thickness over polar regions
Authors: Kergomard Claude , Tanré Didier
Published: February 2008

Field measurements of aerosol content and optical properties of polar atmospheres are difficult and therefore very scarce, especially over ice‐covered marine areas of the Arctic and Antarctic regions. The purpose of this paper is to investigate the opportunity to retrieve these properties from the blurring effect of the atmosphere on high resolution satellite imagery over sea ice. The obtained results are consistent with field measurements and show the reliability of this method in order to monitor temporal changes in the aerosol content of polar atmospheres. Uncertainties remain however in absolute measurements due to the unknown size distribution of aerosol particles and vertical structure of aerosol layers.
A search for five month solar induced periodicity in the stratosphere
Authors: Chandra S.
Published: February 2008

Recent studies of solar UV spectra and various indices of solar activity indicate a strong period at about 5 months. In the 10.7 cm solar radio flux (F10.7), a conventional index for the solar EUV and UV variabilities, the spectral power of the 5 month period is comparable to the well known 27 day solar period. However, in the solar UV flux at 205 nm, directly measured from the Nimbus‐7 SBUV spectrometer, the (spectral) power of the 5 month period is about half that of the 27 day period. This paper examines the possible impact of the 5 month solar period on ozone and temperature at various pressure levels in the stratosphere and discusses the implications of differences in solar forcing at the 27 day and 5 month periods. It is shown that ozone, both in the lower and the upper stratosphere, has a measurable response to solar UV forcing at 27 days. Such a solar response is not observed at 5 month period because of a relatively weaker 5 month solar UV component in the solar signal and a strong interference from dynamical signals associated with planetary wave activity.
Entry and acceleration of He+ in the low latitude boundary layer
Authors: Fuselier S. A. , Peterson W. K. , Klumpar D. M. , Shelley E. G.
Published: February 2008

AMPTE/CCE He+ and H+ observations in the magnetosphere, low latitude boundary layer, and magnetosheath reveal that cold (∼tens of eV) plasmaspheric He+ distributions from the outer magnetosphere convect into the low latitude boundary layer. In the boundary layer, the cold He+ is accelerated and heated to a few keV. The data are resolved in sufficient detail to show that the process of pick up of the cold He+ distribution in the boundary layer H+ flow may not be adequate to explain the observed He+ distributions in the boundary layer.
Stratospheric HBr mixing ratio obtained from far infrared emission spectra
Authors: Park J. H. , Carli B. , Barbis A.
Published: February 2008

Emission features of HBr isotopes have been identified in high‐resolution far‐infrared emission spectra obtained with a balloon‐borne Fourier transform spectrometer in the spring of 1979 at 32°N latitude. When six single‐scan spectra at a zenith angle of 93.2° were averaged, two features of HBr isotopes at 50.054 and 50.069 cm−1 were obtained with a signal‐to‐noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 × 10−11, which is assumed to be constant above 28 km, with an uncertainty of 35 percent. This stratospheric amount of HBr is about the same as the current level of tropospheric organic bromine compounds, 25 pptv. Thus, HBr could be the major stratospheric bromine species.
Cartesian diver observations of double frequency pressure fluctuations in the upper levels of the ocean
Authors: Cox Charles S. , Jacobs David C.
Published: February 2008

Pressure oscillations having a narrow spectrum centered at 0.175 Hz have been measured in the deep sea at depths between 100 and 300 m. At these depths the nonlinear interaction between oppositely directed sea surface gravity waves causes pressure fluctuations, the intensity of which varies inversely with the square of the depth, uninfluenced by microseismic Rayleigh waves propagating on the seafloor below. The observed pressure fluctuations are consistent with the interaction between waves having a unimodel beam pattern whose half beam width is slightly larger than 90 degrees or with a shoreward propagating pencil beam of swells interacting with a small component reflected from the shore.
Regional extent of the S wave reflector beneath the Kanto District, Japan
Authors: Obara Kazushige
Published: February 2008

An S wave reflector was found near the upper plane of the double seismic zone associated with the subducting Pacific plate beneath the southern Kanto district of Japan. Here the areal extent of the reflector is confirmed for a region ranging from 34.5°N to 36.7°N, from the analysis of the travel times of the reflected S waves on 8‐Hz band seismograms. A bend of the reflector is found at about 36°N. It is coincident with the bend of the upper boundary of the subducting Pacific plate obtained from the seismicity analysis. In the middle of the Kanto district the reflector extends to a depth of 120 km, whereas in the northern Kanto district it extends just beneath the volcanic front. The reflector could not be verified for depths shallower than 60 km depth because the reflected S wave cannot be identified at the eastern most stations of the network.
Dynamics of Mars' magnetosphere
Authors: Kennel C. F. , Coroniti F. V. , Moses S. L. , Zelenyi L. M.
Published: February 2008

If Mars has a small intrinsic magnetic moment, Mars' magnetosphere could vary on time scales of a few minutes due to reconnection with the solar wind magnetic field. The day‐side magnetopause will be one or two reflected‐ion Larmor radii from the bow shock. Substorms will have scale‐times of about six minutes. Mars' high ionospheric conductance will virtually stop polar cap convection, and create a magnetic “topological crisis” unless convecting magnetic flux finds a dissipative way to return to the day‐side. The strong magnetic shear induced by magnetospheric convection above the ionosphere could be tearing unstable. The magnetic field might diffusively “percolate” through the tearing layer. This shearing also draws field aligned currents from the ionosphere which could inject few KeV heavy ionospheric ions into the magnetotail.
Implications of the stability and radiative time constant of Triton's atmosphere
Authors: Stern S. Alan
Published: February 2008

This paper examines both Triton's atmospheric escape rates and radiative timescales.

We first calculate the range of plausible atmospheric escape rates and examine the implications of these escape fluxes. If even modest hydrodynamic escape is occurring, escape rates can exceed the ion pickup rates predicted by Delitsky, et al. (1989). This process is expected to develop a torus of gas in orbit around Neptune. If Triton's escape flux exceeds ∼ 1010 cm−2 sec−1, a substantial amount of ancient icy surface topography may have been lost to escape.

We also calculate the radiative timescale in Triton's atmosphere as a function of surface temperature, atmospheric pressure, and composition. It is shown that if N2 obtains saturation vapor pressure equilibrium, then diurnal variations will be negligible. If N2 is far from saturation or if only CH4 is present, then both diurnal and seasonal effects may be expected. Recent observations indicate the presence of decadal‐timescale atmospheric variations. Radiative timescale constraints imply that if these observations are correct, then the present atmospheric pressure is unlikely to much exceed ≈100 mb.
Possible Kelvin‐Helmholtz waves driven by reconnection accelerated flows
Authors: Saunders M. A.
Published: February 2008

We present new observations of highly steepened magnetic signals within the dayside magnetopause current layer, having a period of about 5 seconds. These signals are embedded within a reconnection region and we suggest they may be Kelvin‐Helmholtz waves driven unstable by the velocity shear associated with reconnection accelerated flows. It is due to the low magnetic field strength and consequent high Alfvén Mach number that the signals are confined to the magnetopause. Our data consist of high time resolution magnetic field and plasma measurements from the AMPTE‐UKS satellite.
Analysis of suprathermal electron properties at the magnetic pile‐up boundary of comet P/Halley
Authors: Mazelle C. , Rème H. , Sauvaud J. A. , d'Uston C. , Carlson C. W. , Anderson K. A. , Curtis D. W. , Lin R. P. , Korth A. , Mendis D. A. , Neubauer F. M. , Glassmeier K. H. , Raeder J.
Published: February 2008

Among the plasma discontinuities detected by the GIOTTO spacecraft around comet P/Halley, the Magnetic Pile‐up Boundary, located at about 135,000 km from the nucleus, has a sharpness which was not foreseen by theoretical models. At this boundary, which marks the beginning of the region where the field lines draped around the nucleus have been piled up, the magnetic field jumps sharply. Electron measurements provided by the RPA experiment show that a clear plasma discontinuity coincides with this magnetic feature. Significant changes occur here in the suprathermal electron distribution function. A magneto‐plasma sheet is clearly defined after the boundary. Inside this sheet, close correlations exist between the parameters describing the magnetic field and the electron population. The polytropic equation of state governing the suprathermal electrons in the sheet has been deduced from RPA measurements. Some implications of this law are discussed.
Evidence for thick continental roots beneath South Indian Shield
Authors: Srinagesh D. , Rai S. S. , Ramesh D. S. , Gaur V. K. , Rao C. V. R.
Published: February 2008

Teleseismic P‐wave arrivals recorded at South Indian seismological stations have been used to construct a 3‐D velocity image of the upper mantle beneath this region. Analysis of a suite of models lead us to conclude that an anomalously high velocity region (1–6% contrast) exists in the upper mantle beneath the whole of South Indian shield including the Deccan Traps in the depth range of 60–300 km. In contrast, the westernmost part of the Deccan Traps and its subjacent mantle in the northwest is characterised by a relatively low velocity. This observed low velocity zone may be a still warm remnant of the spreading centre offset eastwards from the Carlsberg ridge, which might have been the dominant source of the flood basalts that flowed over the Deccan Plateau 65 Ma ago. The high velocity upper mantle of the entire South Indian shield is viewed as a continental root formed by a process of geochemical reordering which happens to be more stable.
Multicomponent seismic reflection profiling over an ore‐body structure ‐ A scale model investigation
Authors: Pant D. R. , Greenhalgh S. A.
Published: February 2008

A multicomponent seismic laboratory experiment was conducted to examine the seismic signature of a simulated ore‐body structure. The data were processed using a new form of controlled direction reception (CDR) filter, which operates in tau‐p‐polarisation space, so as to isolate the P and S waves. The four CDR sections showed PP, SS, PS and SP wave reflections, and all mode conversions. From these, the geometry and reflectivity of the ore‐body can be reconstructed. With single component recording and processing, imaging of the ore is extremely difficult.
Ocean loading station displacements observed by VLBI
Authors: Schuh H. , Moehlmann L.
Published: February 2008

Ocean tidal loading causes small displacements of VLBI observing stations that should be taken into account in VLBI data analysis. The a posteriori delay and delay rate errors of least squares fits of those VLBI experiments with stations near ocean coasts and on islands are shown to decrease significantly after correcting the VLBI observables for the ocean loading effect. In extreme cases station coordinates and baseline lengths may change by a few centimeters after applying the ocean loading corrections. Conversely, these results demonstrate that ocean tidal loading can be monitored using high precision VLBI. However, the present global ocean tidal loading model is still inadequate for some stations and should be expanded for future applications.
Pluto's atmosphere near perihelion
Authors: Trafton L. M.
Published: February 2008

A recent stellar occultation has confirmed predictions that Pluto has an atmosphere which is sufficiently thick to uniformly envelope the planet and to extend far above the surface. Pluto's atmosphere consists of methane and perhaps other volatile gases at temperatures below their freezing points; it should regulate the surface temperature of its volatile ices to a globally uniform value. As Pluto approaches and passes through perihelion, a seasonal maximum in the atmospheric bulk and a corresponding minimum in the exposed volatile ice abundance is expected to occur. The lag in maximum atmospheric bulk relative to perihelion will be diagnostic of the surface thermal properties. An estimate of Pluto's atmospheric bulk may result if a global darkening (resulting from the disappearance of the seasonally deposited frosts) occurs before the time of maximum atmospheric bulk. The ice deposited shortly after perihelion may be diagnostic of the composition of Pluto's volatile reservoir.
Upper limits on possible photochemical hazes on Pluto
Authors: Stansberry John A. , Lunine Jonathan I. , Tomasko Martin G.
Published: February 2008

Elliot et al. [1989] invoked a haze layer near the surface of Pluto to explain certain features of a stellar occultation by that planet in June, 1988. The primary requirements for this haze layer were that it achieve unity tangential optical depth at a radius of 1174 km and be essentially transparent above 1189 km. We explore here the possibility that aerosols generated through methane photolysis could be responsible for such a haze layer. A comprehensive model of aerosol production, particle growth, sedimentation and condensation is applied to the atmosphere of Pluto using pressures, temperatures and composition derived from the stellar occultation and other data. We test two atmosphere models proposed in the literature, one from Elliot et al. [1989], and one from Hubbard et al. [1989], as well as a range of optical properties for the particles. In order to produce a haze with unity tangential optical depth at 1174 km, we had to use an aerosol mass production rate equal to twice the total methane dissociation rate due to solar UV expected for Pluto and assume that the particles produced were 10 times more absorbing than those in other hazes in the outer solar system. The possibility of condensation in the lower atmosphere was considered but did not result in distinctly different haze optical depths. If a photochemical haze on Pluto was responsible for the occultation lightcurve measured by Elliot et al., operation of a photochemical system different from those on Titan, Uranus or Neptune is indicated. Alternatives include near surface condensation processes driven by circulation, and the possibility that the occultation light curve can be explained in its entirety by temperature effects as proposed by Hubbard et al. [1989].
Southward magnetic field in the neutral sheet produced by wavy motions propagating in the dawn‐dusk direction
Authors: Nakagawa T. , Nishida A.
Published: February 2008

Magnetic field observations by IMP 6 at about 20 RE tailward from the earth show that magnetic field in the neutral sheet sometimes takes north and south polarities alternately at successive crossings. This can be understood by wavy motion of the neutral sheet that propagates in the dawn‐dusk direction in the presence of the dawn‐dusk component of the magnetic field. Such wavy motion of the neutral sheet can be generated by the Kelvin‐Helmholtz instability if the dawn‐dusk flow of only several tens of km/s is present.
Collisionless reconnection in a quasi‐neutral sheet near marginal stability
Authors: Pritchett P. L. , Coroniti F. V. , Pellat R. , Karimabadi H.
Published: February 2008

Particle simulations are used to investigate the process of collisionless reconnection in a magnetotail configuration which includes a pressure gradient along the tail axis and tail flaring. In the absence of electron stabilization effects, the tearing mode is stabilized when the ion gyrofrequency in the normal field exceeds the growth rate in the corresponding one‐dimensional current sheet. The presence of a low‐frequency electromagnetic perturbation in the lobes can serve to destabilize a marginally stable current sheet by producing an extended neutral‐sheet region which can then undergo reconnection. These results help to explain how X‐type neutral lines, such as those associated with the onset of magnetospheric substorms, can be formed in the near‐earth plasma sheet.
An elementary model of a tornado
Authors: Kenyon Kern E. , Kenyon Douglas C.
Published: February 2008

An elementary model of a tornado is presented that is based on the concept of downward vertical velocity everywhere within the tornado. A tornado forms because some air, which is denser than the surrounding air, falls from the cloud to the ground. The funnel shape is then accounted for qualitatively by conservation of mass, and conservation of angular momentum explains the high wind speeds at the narrow end of the funnel. The outward centrifugal force on the rotating winds is balanced by an inward pressure gradient. Because of the dynamic effect of the falling air, compared to the static effect of the environment, the pressure inside the funnel is always lower than that outside the funnel, and the pressure difference increases with decreasing altitude.
Pb isotopic tracers of the Cretaceous‐Tertiary extinction event
Authors: Galer S. J. G. , Macdougall J. D. , Erickson D. J.
Published: February 2008

The global excess of Ir in sediments at the Cretaceous‐Tertiary (K‐T) boundary has been attributed to either a meteorite impact or enhanced volcanism (e.g. Deccan Traps). The isotopic composition of Pb associated with this Ir provides a test of these hypotheses because meteoritic Pb is isotopically quite distinct from Pb of volcanic or continental origin. Pb abundances and isotopic compositions of pelagic oozes from DSDP Site 577A (Shatsky Rise, NW Pacific) measured in this study show little change over the deposition interval of Ir‐rich sediment (∼10 cm). However, a Pb enriched layer with a more radiogenic isotopic composition is found in the basal ∼0.5 cm of the Tertiary. These observations appear to preclude the Ir excess in these sediments originating as impact fallout from a stony meteorite although an iron meteorite impactor cannot be excluded. Any Pb flux accompanying Ir in volcanogenic aerosols from the Deccan Traps should be considerable. However, the boundary Pb ‧spike‧ does not isotopically resemble known Deccan Trap lavas. There is isotopic overlap with coal ash although the lack of correlation between soot and Pb abundance precludes any simple relationship between the two. Overall, any wind pattern changes following the K‐T ‧event‧ were apparently short‐lived as neither airborne sources of Pb nor their magnitude to the then central Pacific were affected while the Ir enriched sediments were being laid down.
Central Washington seismicity: Evidence for a reactivated buried continental rift and northwest‐trending structural zones
Authors: Johnson Peggy A.
Published: February 2008

Analysis of central Washington seismicity of the past two decades reveals some interesting features. Shallow seismicity and deep seismicity occur as different geographic distributions. Concentration of seismicity along north‐ to northwest‐oriented trends appears to be related to a buried continental rift and possible associated fault zones. Hypothesized extensions of the Chiwaukum graben and Straight Creek fault systems are plausible structural controls on the seismicity.
Equation of state of CaSiO3 perovskite to 96 GPa
Authors: Tarrida Martine , Richet Pascal
Published: February 2008

The CaSiO3 perovskite has been synthesized in a laser‐heated diamond‐anvil cell at initial pressures ranging from 15 to 85 GPa. Chemical microanalyses of the quenched product show negligible solubility in the CaSiO3 perovskite of aluminum from the ruby added for pressure measurements. The compression of CaSiO3 perovskite has been measured to 96 GPa with X‐ray methods. The results do not show a significant deviation of Ko′ from 4, and with a Birch‐Murnaghan equation of state we obtain a 1‐bar molar volume Vo = 45.60 ± 0.10 Å³ and a bulk modulus Ko = 275 ± 15 GPa. This perovskite may be an "invisible" component of the lower mantle in view of the similarity of its density with that given by the standard Earth model, PREM.
Profiles of nitric oxide in the upper stratosphere
Authors: Kondo Y. , Iwata A. , Aimedieu P. , Matthews W. A. , Sheldon W. R. , Benbrook J. R.
Published: February 2008

Data from a chemiluminescent NO detector, and an in situ ozone instrument are presented. The measurements were made on September 17, 1987 and on June 18, 1988 aboard high altitude balloons launched from the French CNES Balloon Launching Center at Aire sur l'Adour (44°N, 0°W) and from Gap (44.5°N, 6°E). The NO measurements above 32 km are more accurate than previous determinations due to a more precise regulation of the sample flow rate at pressures down to 2 mb, with a reduced ozone/oxygen flow rate. NO profiles between 25 and 40 km were obtained during a period of slow descent in the late morning of September 17, 1987 and in the early afternoon of June 18, 1988. The two NO profiles obtained between 35 and 40 km differ by less than 10%. The average NO concentration was 9 ppbv at 35 km, increasing with altitude to 11.5 ppbv at 40 km. Below 34 km, the NO concentration in September was 20 to 35% larger than that in June. The difference in the temperature profile significantly contributes to the observed change in the NO concentration through the change in the [NO]/[NOx] ratio. These measurements provide an accurate determination of the daytime mid‐latitude NO concentration in the upper stratosphere in summer and autumn.
Teleseismic body wave analysis of the 1988 Armenian Earthquake
Authors: Pacheco J. F. , Estabrook C. H. , Simpson D. W. , Nábělek J. L.
Published: February 2008

Long‐period and broadband body waves from 14 digital seismic stations are used to investigate the rupture process of the December 7, 1988 earthquake near Spitak, Armenia, USSR. The inversion of these data gives the following centroidal source parameters: strike 299°, dip 64°, rake 151°, depth 6.3 km and seismic moment 1.5×1019 Nm, indicating that on average the earthquake had a strike‐slip mechanism with a substantial reverse component. The broadband waveforms, however, show significant complexity; they are best fit with a source model that includes three sub‐events, very similar in size, but with distinct focal mechanisms and locations. Rupture apparently initiated as a shallow reverse fault at a point of maximum bending on a right‐lateral strike‐slip fault, and then extended bilaterally, first towards the southeast and then towards the west. This interpretation agrees with the aftershock distribution and fault lineations observed on LANDSAT images.
Maximum scales for preserving flux tube content in radial diffusion driven by interchange motions
Authors: Vasyliūnas Vytenis M.
Published: February 2008

Plasma in the inner magnetosphere of Jupiter is commonly assumed to be transported radially by fluctuating interchange motions, carrying, on the average, high‐density flux tubes outward and low‐density flux tubes inward. On a coarse‐grained view, this is a diffusion process; viewed on a sufficiently fine scale, high‐density outward‐diffusing tubes and low‐density inward‐diffusing tubes might be observable. However, the required fine scale is much smaller than the characteristic size of circulating eddies of the interchange motion; as a consequence of repeated bifurcations of the flow as the eddy pattern changes randomly, only flux tubes of cross‐sectional dimension smaller than a typical eddy size by the square of (eddy size divided by diffusion distance) have a reasonable chance of preserving their initial plasma content. Energy‐dependent guiding center drifts will randomize and smooth out density variations even on this fine scale if the plasma energy spectrum is wide enough; from a simple model of gradient drifts, the required energy width is proportional to the magnetic flux through a typical eddy divided by the diffusion time. The absence of fine‐grained density fluctuations in the Voyager plasma observations can be explained by such smoothing from gradient drifts, given the observed typical ion thermal energy spread of some 40 eV and the assumption that the typical eddy size is no larger than about 0.7 Jovian radii.
A possible station bias in travel time measurements reported to ISC
Authors: Grand Stephen P.
Published: February 2008

A station bias in the travel‐times of P‐waves may exist in the International Seismological Centre (ISC) data base. It appears that low gain seismographs report systematically late arrival times. Average station delays confirm this with low gain stations generally slower than high gain stations.
NaHCO3: A source of Na atoms for sudden sodium layers?
Authors: von Zahn Ulf , Murad Edmond
Published: February 2008

We consider the case of sudden sodium layers which have been reported in the lower E region of the ionosphere. We suggest that dissociative electron attachment to NaHCO3, NaHCO3 + e → Na +HCO3−, can explain some of the observations, in particular at altitudes above 95 km. This process would produce Na efficiently only in the case where a plasma of high density is injected into the sodium layer. The rate constant for the reaction is estimated to be of the order of 10−8cm3 s−1 by analogy with similar species and by derivation from the observed geophysical parameters.
Ozone depletion in the Arctic Vortex at alert during February 1989
Authors: Evans W. F. J.
Published: February 2008

Evidence for an apparent chemical depletion of ozone was observed in the Arctic polar vortex during February 1989 in the form of a depleted layer in the ozone mixing ratio altitude profile. The measurements of the distribution of ozone partial pressure in the polar vortex were conducted with ECC ozonesondes which covered the altitude range from 1 to 30 km. These balloon measurements demonstrated a depleted layer in the profile at altitudes from 18 to 24 km. The meteorological ozonesonde balloon ascents took place from January 24 to February 22 1989 from Alert, Canada at 82.5 N. A comparison of the late February ozone profiles with the late January ozone profiles indicates that the depletion was due to a process which may have occurred while the polar air was partially in sunlight. The depleted layer was similar to that observed from the South Pole base in the Antarctic inside the ozone hole in mid‐September. The depletion may have commenced at high altitudes above 22 km and moved downwards during February in a manner similar to the process in September in the Antarctic. Polar stratospheric clouds were previously observed in mid‐January over the altitude regime from 16 to 24 km.
Analysis of A Deep “Non Double Couple” Earthquake Using Very Broadband Data
Authors: Kuge Keiko , Kawakatsu Hitoshi
Published: February 2008

We analyze the source mechanism of a deep earthquake beneath Japan on January 1, 1984, whose Harvard centroid moment tensor (CMT) solution significantly deviates from a double couple mechanism. The broadband P‐wave ground displacement records show the presence of several distinct phases whose relative amplitudes vary among the stations. We perform very broadband waveform analyses over four different frequency bands: CMT inversion (surface waves (4∼5mHz) and long‐period body waves (12∼20mHz)), waveform inversion using the long‐period P, pP and SH waves (∼0.04Hz), and broadband P‐ and pP‐wave waveform analysis (0.03∼1Hz). We show that the large non double couple solution observed at long periods (>25 sec) is very likely to be a manifestation of the presence of subevents with different double couple mechanisms in a single rupture sequence.
Total ozone during the 88‐89 Northern Hemisphere winter
Authors: Newman Paul , Stolarski Richard , Schoeberl Mark , Lait Leslie R. , Krueger Arlin
Published: February 2008

Total ozone values measured by the Total Ozone Mapping Spectrometer (TOMS) during January, February and March 1989 are analyzed. During this period, polar total ozone values did not reveal clear depletions, although average winter total ozone values indicate that a 2–6% ozone reduction has occurred in northern mid to high latitudes over the last 10 years. Rapid total ozone increases were seen during mid‐February, resulting from a wave 2 major stratospheric warming. In order to track polar air over the warming period, total ozone trends are further analyzed using Ertel's potential vorticity.
Stratospheric temperatures during AASE: Results from Stratan
Authors: Rood Richard B. , Newman Paul A. , Lait Leslie R. , Lamich David J. , Chan K. Roland
Published: February 2008

Comparisons of temperatures from the research analysis system STRATAN to radiosonde data, Meteorological Measurement System (MMS) data, and the National Meteorological Center (NMC) analyses are presented for the Airborne Arctic Stratospheric Expedition (AASE). The STRATAN analyses show consistent quality throughout AASE. The comparisons to MMS show that STRATAN more accurately represented low temperatures than NMC. This, coupled with forecast quality, show that STRATAN temperature fields are a valuable tool for diagnosing and forecasting polar stratospheric clouds.
Near UV atmospheric absorption measurements of column abundances during Airborne Arctic Stratospheric Expedition, January – February 1989: 1. Technique and NO2 observations
Authors: Wahner Andreas , Callies Jörg , Dorn Hans‐Peter , Platt Ulrich , Schiller Cornelius
Published: February 2008

Spectroscopic measurements of column abundances of NO2 were carried out from the NASA DC‐8 airplane during the Airborne Arctic Stratospheric Expedition in January and February 1989. Stratospheric airmasses inside and close to the polar vortex were found to be highly depleted of NO2 with lowest vertical column abundances of NO2 below 2 × 1014 cm−2 compared to abundances of 3 – 5 − 1015 cm−2 south of 50° N in winter (WMO, 1985).
Near UV atmospheric absorption measurements of column abundances during Airborne Arctic Stratospheric Expedition, January – February 1989: 3. BrO observations
Authors: Wahner Andreas , Callies Jörg , Dorn Hans‐Peter , Platt Ulrich , Schiller Cornelius
Published: February 2008

Column abundances of BrO were measured during the Airborne Arctic Stratospheric Expedition from January 6 to February 9, 1989 by near UV absorption spectroscopy. BrO was detected during eight flights by scattered sunlight observations during twilight and direct moon light observations during the night. The daytime vertical column abundances of BrO varied between 2 × 1013 cm−2 and 13 × 1013 cm−2 and are consistent with observed OClO column abundances and chemical model calculations. The nighttime presence of BrO suggests different vertical profiles of BrO and ClO.
Three dimensional simulation of hydrogen chloride and hydrogen fluoride during the Airborne Arctic Stratospheric Expedition
Authors: Kaye Jack A. , Douglass Anne R. , Rood Richard B. , Stolarski Richard S. , Newman Paul A. , Allen Dale J. , Larson Edmund M. , Coffey Michael T. , Mankin William G. , Toon Geoffrey C.
Published: February 2008

Simulations of the evolution of stratospheric distributions of hydrogen chloride (HCl) and hydrogen fluoride (HF) have been carried out for the period of the Airborne Arctic Stratospheric Expedition (AASE) with a three‐dimensional chemistry‐transport model. Simulations were performed assuming only homogeneous gas phase chemistry for HF and both homogeneous gas phase and heterogeneous chemistry for HCl. Results show heterogeneous loss of HCl is needed to provide agreement with infrared column measurements. Estimates of the impact of heterogeneous loss on the global HCl distribution are obtained from the model. Reductions of HCl due to heterogeneous loss are calculated to be localized to regions of high vorticity, even after more than a month of integration.
Effects of atmospheric transport on column abundances of nitrogen and chlorine compounds in the Arctic stratosphere
Authors: Yatteau John H. , Wofsy Steven C. , Salawitch Ross J. , McElroy Michael B. , Schoeberl Mark R. , Lait Leslie R. , Newman Paul A. , Torres Arnold , Jorgensen Torben , Mankin William G. , Coffey Michael T. , Toon Geoffrey C. , Loewenstein Max , Podolske James R. , Strahan Susan E. , Chan K. Roland , Proffitt Michael H.
Published: February 2008

In the absence of heterogeneous processes, distributions of NOy, HNO3, Clx and HCl in the polar winter stratosphere should be determined by transport. A model simulating distributions of these species in the arctic for January and February 1989 is developed using observed fields of potential vorticity and potential temperature. Comparison of model results with column measurements from the DC‐8 indicates conversion of NOx to HNO3, condensation of HNO3, conversion of HCl to ClNO3, and conversion of HCl plus ClNO3 to an unmeasured species. Heterogeneous processes strongly affect abundances of NOy and Clx species in the winter arctic stratosphere.
Estimation of the solar Lyman alpha flux from ground based measurements of the Ca II K line
Authors: White O. R. , Rottman G. J. , Livingston W. C.
Published: February 2008

Measurements of the solar Lyman alpha and CaII K from October 1981 to April 1989 show a strong correlation (r=.95) that allows estimation of the Lyman alpha flux at 1 AU from 1975 to December 1989. Our estimated Lyman alpha strength of 3.9 × 1011±.15 × 1011 photons/s cm2 on 7 December 1989 is at the same maximum levels seen in Cycle 21. Relative to other UV surrogates (sunspot number, 10.7 cm radio flux, and HeI 10830 line strength), Lyman alpha estimates computed from the K line track the SME measurements well from solar maximum, through solar minimum, and into Cycle 22.
Amplification of critical velocity ionization by a pulsed neutral beam
Authors: Lai Shu T. , McNeil William J. , Murad Edmond
Published: February 2008

Numerical results of computer simulations on critical ionization velocity (CIV) discharges in pulsed neutral beams are presented. In a typical CIV scenario, neutral molecules as well as newly created ions are traveling across the ambient magnetic field. The ions slow down as they transfer kinetic energy to the electrons via plasma waves. For a single pulse of neutral gas, there is a finite contact time between the beam and the plasma; the contact time is governed by the length of the pulse and the velocity of neutrals. The injection of multiple pulsed neutral beam into a magnetized plasma has the advantage that succeeding pulses may extend the effective contact time of a single pulse. Using the particle‐in‐cell method of computer simulations, we show a detailed time history of the CIV process as a result of the interplay between plasma (wave‐particle) interactions and collisional (ionization, charge exchange) processes. It is found that ions slowing down and lagging behind the pulses can still contribute to electron heating. Simulation results show that CIV in a multiple pulsed beam is more efficient than that in a single continuous pulse.
The use of magnetic susceptibility and its frequency dependence for delineation of a magnetic stratigraphy in ash‐flow tuffs
Authors: Eick Peter M. , Schlinger Charles M.
Published: February 2008

Variations in the grain size, amount, and mineralogy of magnetic phases in layered volcanic rocks define a mapetic stratigraphy that can be identified by means of magnetic susceptibility measurements. In ash‐flow tuffs, grain size and other variables that control susceptibility are to a large extent a function of the cooling and alteration history. The phases responsible for the susceptibility of ashflow tuffs consist of post‐emplacement high‐temperature precipitates of Fe‐oxides in volcanic glass, and the phenocrystic Fe‐Ti oxides. At Yucca Mountain, Nevada, laterally‐continuous high‐susceptibility (∼ 10−2 SI) horizons exist in the Paintbrush Tuff due to the presence of either precipitates or phenocrystic Fe‐Ti oxides. The frequency dependence of magnetic susceptibility, x(ω), can be used to discriminate between horizons with supeiparamagnetic predpitates and horizons with multi‐domain phenocrystic material. The x(ω) exhibits a 26% decrease per decade of increasing frequency for precipitate grain sizes where the siperparamagnetic single‐domain state gives way to stable single‐domain behavior, and thus x(ω) offers an indirect method for rapid estimation of magnetic grain sizes. The interpretation of variations established by field and laboratory susceptibility data has been constrained by petrography and transmission electron microscopy (TEM).
On the potential importance of transient air flow in advective radon entry into buildings
Authors: Narasimhan T. N. , Tsang Y. W. , Holman H. Y.
Published: February 2008

We have investigated, using a mathematical model, the temporal variations of air flux within the soil mass surrounding a basement in the presence of time dependent periodic variations of barometric pressure and a persistent under‐pressure at the basement. Our results of transient air flow show that for a homogeneous soil medium, the effects of barometric fluctuations are most significant in the cases where soil permeability to air is low and the fluctuation frequency is high. In these cases, the barometric fluctuation can greatly enhance the magnitude of fluxes as well as introduce flow direction reversals from surrounding soil into the basement. These large fluxes with direction reversals have strong implications in regard to advective transport of radon. Our results suggest that the transient oscillations have to be accounted for in quantifying radon entry into buildings. In the actual field set up, the transient behavior will be further influenced by soil permeability heterogeneity, by soil moisture variations, and by the effects of multiple periodic components in the barometric pressure fluctuations.
Toward understanding the fate of dust lost from the Martian satellites
Authors: Horanyi M. , Burns J. A. , Tatrallyay M. , Luhmann J. G.
Published: February 2008

We have investigated the dynamics of small dust grains ejected from the Martian satellites, considering both the solar radiation perturbation and electromagnetic forces since the grains move in a magrietized plasma. Lorentx forces can dramatically change the nature of the trajectories, resulting in, for example, prolonged for submicron‐slzed grains moving through our idealized iaodel. Though temporal changes of the solar wind were ignored and we only followed grains for 20 days or less, we suggest that a permanent, non‐uniform and time‐dependent dust halo of grains predominantly around 0.1 μm may exist about Mars.
Venus mantle‐Mars planetosphere: What are the similarities and differences?
Authors: Nagy Andrew F. , Gombosi Tamas I. , Szego Karoly , Sagdeev R. Z. , Shapiro V. D. , Shevchenko V. I.
Published: February 2008

The available data related to the mantle/planetosphere regions of both Mars and Venus are reviewed. It is shown that there are significant similarities in these regions at the two planets. These are: 1) a transition region between the magnetosheath and the ionosphere dominated by heavy, planetary ions; 2) a transition region in which the electron population is different from both the shocked solar wind and the photoelectron ones; 3) a magnetic signature near the transition boundary; and 4) the presence of low frequency electric waves within the transition region.
Observations of the magnetic fluctuation enhancement in the Earth's foreshock region
Authors: Le G. , Russell C. T.
Published: February 2008

Upstream waves have been postulated to be a major source of energy for the dayside magnetic pulsations within the magnetosphere. Thus it is of interest to determine over what frequency range in the ion foreshock the power of fluctuations in the solar wind is enhanced. We have examined the magnetic field data from pairs of spacecraft when they are on either side of the ion foreshock boundary. We find that the power of magnetic fluctuations is enhanced only at periods less than about two minutes, not at longer periods. Thus the upstream waves may contribute to Pc 3 and Pc 4 pulsations in the dayside magnetosphere, but they can not be directly responsible for the longer period waves.
An effect of source on Po/So generation evidenced by a deep‐focus earthquake
Authors: Nagumo Shozaburo , Ouchi Toru
Published: February 2008

Po/So phases generated by a deep‐focus earthquake (focal depth: 360 km) were observed at epicentral distances between 11° and 14° in the northwestern Pacific by an ocean‐bottom seismometer (OBS) array. The apparent velocity of Po was about 8.3 km/s, which is higher than is observed for shallow‐focus earthquakes. The high‐frequency, long‐duration features of Po/So wave trains appear to be related to observed high Q's in the deep dipping seismic zone. Lateral propagation of Po/So associated with a deep‐focus earthquake seems to begin when the P wave travels up the subducting slab and reaches the upper lithosphere beneath the trench axis. Also, a waveguide phenomenon occurs in the dipping subduction slab itself. Wave trains generated near the source should be taken into consideration in the theory of Po/So generation.
Frequency dependent attenuation in the crust
Authors: Toksöz M. Nafi , Mandal Batakrishna , Dainty Anton M.
Published: February 2008

The shear wave attenuation (Q−l) in the crust beneath the northeastern US and Scandinavia is determined as a function of depth and frequency using theoretical modeling of complete waveforms in comparison with observed data. To determine attenuation in the upper crust of the northeastern US, short period (0.25 < T < 2 sec) Rg waves recorded by linear arrays of seismometers are used. For Scandinavia Rg and Lg waves are combined to extend the investigation into the deeper crust. The combination of Rg waves and short period (T < 1.0 sec) Lg waves makes it possible to determine attenuation as a function of depth and frequency in the crust, parameterized as Q = Qo fζ. To match the observations, theoretical models for three mechanisms that contribute to attenuation in the crust‐frequency independent anelastic (Qa−1), and frequency dependent fluid flow (Qf−1) and scattering (Qs−1)–are considered. The best fitting models require low Q (Q0 < 100) in the shallow crust that increases with increasing frequency as f0.5 above 1 Hz. In the middle crust between about 2 to 10 km depth Q is moderate (100 < Q0 < 500) with a frequency dependence of f1. In the lower crust, the attenuation is very low (Q ≥ 500) and its frequency dependence is difficult to establish. The low intrinsic Q, and the frequency dependence, in the uppermost crust can be explained by fluid flow in fractures. In the middle crust the frequency dependence suggests scattering. The increase of Q in the lower crust is most likely due to annealing of microcracks under pressure and temperature as observed in the laboratory.
Fault parameters and tsunami excitation of the May 23, 1989, MacQuarie Ridge Earthquake
Authors: Satake Kenji , Kanamori Hiroo
Published: February 2008

The Macquarie Ridge earthquake of May 23, 1989, is one of the largest events in the last decade. Furthermore, it is the largest strike‐slip earthquake ever recorded instrumentally. We analyzed long‐period surface waves and body waves recorded at global networks (GDSN, IRIS, GEOSCOPE, and IDA) to estimate the fault parameters and computed tsunamis from the estimated parameters. The Centroid Moment Tensor (CMT) solution from surface waves shows that the mechanism is almost pure strike‐slip with one of the nodal planes parallel to the strike of the Macquarie Ridge. The seismic moment is 1.6 × 1021 Nm (× 1028 dyn·cm) and the corresponding moment magnitude is Mw =8.1. Teleseismic P and S waves from 10 stations with good azimuthal coverage are used to model the temporal and spatial distribution of the subevents. Four subevents are located sequentially from south to north along the ridge system in about 30 sec. All of them have a mechanism similar to the CMT solution. The fault length is estimated to be about 120 km from the subevent and the aftershock distributions. The rapture propagates from south to north at a relatively high speed. The average slip on the fault depends on the estimate of the fault width, but is probably larger than 9 m. A large strike‐slip earthquake like this event produces significant vertical displacements on the ocean bottom and excites tsunamis. Computation of tsunamis using the estimated fault parameters predicts that small tsunamis are expected at Australia and New Zealand. In fact, small tsunamis were observed on the southern coast of Australia.
The 1989 MacQuarie Ridge Earthquake and its contribution the regional seismic moment budget
Authors: Anderson Helen J.
Published: February 2008

The Macquarie Ridge earthquake (1989 May 23; Mw 8.2) occurred in a region of complex tectonics that marks the southern continuation of the plate boundary (Pac‐Aus) that runs through New Zealand. The first motion focal mechanism (from WWSSN and regional station polarities) indicates dominantly strike‐slip movement (strike 025°, dip 80°, rake 180°), probably dextral on the northeast striking nodal plane. The plate boundary south of New Zealand appears to be segmented and marked by linear bathymetric highs with distinctive trends. The distribution of shallow seismicity follows these bathymetric trends. The moment tensors for the largest earthquakes (Ms > 6.0) occurring on five distinctive segments of the plate boundary, for the period 1964–1989, have been summed and compared with the deformation predicted by the plate motions. Recurrence times of the largest earthquakes in each segment, determined by assuming that all deformation occurs seismically along the Macquarie Ridge Complex (MRC), generally show longer recurrence times than those determined from the historic record. These results suggest that during the last 70 years there has been more seismic moment release along the MRC than predicted by the plate motions. The preferred explanation is that this century is a seismically overactive period which is part of a natural episodicity of quiescence and overactivity. Alternative explanations include complex plate interactions resulting from proximity of the plate boundary to the instantaneous pole of rotation and/or the existence of a southeast Australian microplate.