bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous in situ magnetospheric and ionospheric detection of detached plasmas
Authors: Miller Nathan J. , Grebowsky Joseph M.
Published: February 2008

On January 19, 1972, in situ measurements by instruments on Explorer 45, orbiting in the magnetosphere near the equatorial plane, and ISIS 2, in a circular polar orbit at 1400 km, simultaneously detected patches of enhanced ionization outside the main body of the plasmasphere. The magnetospheric plasma region extended between L values 3.4‐4.8 and the ionospheric electron density enhancement extended between L values 3.6‐4.4. The two plasma features were detected near 22 hours MLT. From the observations, including some made before and after the simultaneous measurements, we infer that the plasma density enhancement persisted for more than 5 hours and extended over at least 2 hours in magnetic local time near L=5. Our results provide experimental evidence that some detached magnetospheric plasma regions are signatures of a flux tube containing enhanced ionization throughout a volume extending from the topside ionosphere out to the equator.
The nature of the gravity anomalies associated with large young lunar craters
Authors: Dvorak J. , Phillips R. J.
Published: February 2008

The negative Bouguer anomalies (i.e., mass deficiencies) associated with four young lunar craters are analyzed. Model calculations based on generalizations made from studies of terrestrial impact structures suggest that the major contribution to the Bouguer anomaly for these lunar craters is due to a lens of brecciated material confined within the present crater rim crest and extending vertically to at least a depth of one‐third the crater rim diameter. Calculations also reveal a systematic variation in the magnitude of the mass deficiencies with the cube of the crater diameter.
The relationship between field‐aligned current, carried by suprathermal electrons, and the auroral arc
Authors: Arnoldy R. L.
Published: February 2008

Data from four auroral sounding rockets, which directly measured field‐aligned currents with particle detectors, are presented. The largest fraction of the field‐aligned current carried by electrons was 1) due to precipitating electrons of energy <1 keV; 2) located spatially at the edges of the auroral luminosity. A model is suggested in which these currents couple the ionosphere to the magnetosphere and produce the pre‐breakup auroral arc.
High‐silica glass inclusions in olivine of Luna‐24 samples
Authors: Roedder Edwin , Weiblen Paul W.
Published: February 2008

Optical examination of nine polished grain mounts of Luna‐24 drillcore material (0.09‐0.50 mm size) revealed melt inclusions in olivine crystals. Two inclusions consist of clear glass with exceptionally high Si, yet contain no visible daughter minerals, and have had no reaction effects with the olivine walls. Their compositions (one has SiO2 93.8, Al2O3 1.51, FeO 2.32, MgO 1.61, CaO 0.06, Na2O <0.05, K2O 0.11, total 99.41%; the other is similar) are unique and quite unlike the high‐Si, high‐K melt of granitic composition that is found as inclusions in late‐stage minerals of these (and the Apollo) samples, from silicate liquid immiscibility. The host olivines are Fo73 and Fo51. The origin of the melt in the inclusions and the lack of reaction effects are perplexing unsolved problems.
Is the common definition of the Mie‐Grüneisen equation of state inconsistent?
Authors: Mulargia Francesco
Published: February 2008

The high temperatures typical of shock wave phenomena and planetary interiors require the use of anharmonic models accounting also for electronic effects in their description. By using a generalized form of the Grüneisen γ function and its formulation in anharmonic lattice dynamics we find that at temperatures of a few thousand degrees Kelvin γ is: 1) dependent on temperature as well as on volume; 2) different from the thermodynamical Grüneisen parameter
by a quantity of the same order of magnitude of γ. This is not in contradiction with experimental data showing for many solids a quasi‐independence of γth on temperature for T up to 1000°C.
Stereographic cloud heights from imagery of SMS/GOES satellites
Authors: Minzner R. A. , Shenk W. E. , Teagle R. D. , Steranka J.
Published: February 2008

Stereographic pairs of SMS/GOES images, generated simultaneously by the spin‐scan cameras of each of two geostationary satellites (SMS 1 and SMS 2, separated by 32 degrees of longitude on February 17, 1975), have been analyzed photogrammetrically to yield cloud heights with a two‐sigma uncertainty of 500 meters. The 32‐degree angle between the image plane of the two satellites, plus the distortions involved in transferring the image of a nearly full hemisphere of the earth onto a plane, required the development of a special instrument to permit stereographic compilation. Cloud heights measured stereographically compared favorably with heights of the same clouds measured by radar and IR methods. The same SMS image pairs were used to measure mountain‐top heights with a mean deviation of 0.24 km from cartographic values.
Effect of internal gravity waves upon night airglow temperatures
Authors: Noxon J. F.
Published: February 2008

Large quasi‐periodic fluctuations are observed simultaneously in the rotational temperature of the nightglow emission from both O 2 (¹Σ g ) and OH. The fluctuation amplitude usually is several times larger in the former and the O 2 (¹Σ g ) fluctuations often lead those of OH in phase. This behavior is consistent with that expected for internal gravity waves propagating upward over the ˜ 10 km vertical separation between the two emission layers. The most prominent periods are 1‐2 hours and the full range of oscillation in temperature at 95 km sometimes approaches 100° K.
Search for time‐dependent seismic P travel times from mining explosions near Centralia, Washington
Authors: Chou Chee Wu , Crosson Robert S.
Published: February 2008

A series of mining explosions, occurring from April 1972 to May 1975, have been analyzed for evidence of travel time variations and hence intrinsic P velocity variations in the Puget Sound region. Since the area is seismically active, it is important to establish observational bounds on velocity changes that might occur due to phenomena such as stress changes or dilatancy effects. From 475 explosions well recorded on 10 stations, relative P wave arrival times are calculated using one station as a reference. After major source migration effects are identified and removed, stations receiving sharp P arrival onsets show stability within 0.2 sec and median values for each month of data show less than 0.1 sec variation. Although time‐dependent velocity changes may contribute to the remaining unexplained residual variations, minor source migration, signal variability, and related reading error account for most of them. Detailed source position data are necessary to properly identify the source of time‐dependent, residual anomalies from explosion records.
Ultraviolet absorption cross sections of hydrogen peroxide
Authors: Lin C. L. , Rohatgi N. K. , DeMore W. B.
Published: February 2008

The absorption cross sections of hydrogen peroxide vapor in the wavelength range from 195 to 350 nm were determined at 296 K. The absorption cross sections of neutral aqueous solutions of hydrogen peroxide were also measured in the same wavelength range. The results are compared with those of other workers, and calculated photodissociation coefficients of atmospheric hydrogen peroxide are presented.
An empirical model of the interrelationship of electron temperature and density in the daytime thermosphere at solar minimum
Authors: Brace L. H. , Theis R. F.
Published: February 2008

Measurements of the electron temperature and ion density made by Langmuir probes on Atmosphere Explorer C between December 1973 and December 1974 have been used to investigate the altitude dependence of the relationship between these parameters in the sunlit thermosphere. The data from 1600 perigee excursions provided measurements between 130 and 400 kilometers altitude, between 50 North and South latitude, and for solar zenith angles of less than 85°. Within these bounds we find that the temperature and density exhibit a well defined relationship that varies with altitude. At altitudes below 200 kilometers where electrons are cooled primarily by collisions with the neutral gas, the electron temperature is nearly independent of the plasma density, both parameters increasing with altitude. At higher altitudes where electrons are increasingly cooled by collisions with ions, the temperature and density begin to exhibit an inverse relationship. The uniqueness of this behavior over a wide range of latitudes, longitudes, local times and seasons leads us to suggest that this model may be useful in estimating the electron temperature whenever measurements of plasma density are available from other sources. We also plan to use the model to identify within the AE‐C data the existence of geophysical factors that affect the electron thermal balance. However, the uniqueness of the Te(Ni, h) relationship implies that spatial and temporal variations of the heat sources and sinks may not be large for daytime non‐auroral conditions.
Is the Moon really as smooth as a billiard ball? Remarks concerning recent models of sputter‐fractionation on the lunar surface
Authors: Hapke Bruce , Cassidy William
Published: February 2008

Two recent discussions of chemical and isotopic fractionation by solar wind sputtering (Pillinger et al., 1976; Switkowski et al., 1977) are not applicable to the moon because the authors have failed to include major effects caused by the real geometry of the lunar surface. The complex reentrant micromorphology of the lunar soil drastically affects sputter‐fractionation because most of the sputtered species do not leave the moon, but strike surfaces which are partially shielded from further sputtering. At these sites fractionation is effectively controlled by desorption and angular sputtering effects rather than by sputtering yields. The mass ratio of matter which has been sputter‐deposited to that in the sputter‐altered transition layers on individual grains exceeds 100∶1.
Centrifuge modeling of earthquakes
Authors: Liu Hsi‐Ping , Hagman Ronald L. , Scott Ronald F.
Published: February 2008

The major problem in scale modeling of crustal tectonic processes, namely, the requirement for a brittle modeling material of extremely low strength (∼0.1 bar) can be overcome by doing model tests under artificial gravity in a centrifuge. When conditions of dynamic similarity are observed, scale modeling, because of its controlled nature, can be an important tool supplementing field investigation, theoretical study, and numerical simulation of crustal tectonic processes. Fracture events by simulated tectonic stress loading in a model thrust fault (model dimensions: 20 cm depth × 25 cm × 27 cm) have been generated when the model is subject to 50 g in a centrifuge of 1.53 m radius. Measurements obtained are: the total loading force, the stress change at one location inside the fault zone, and model seismic signals recorded on the model top surface. With use of a scaled brittle model material, the model scales up to a prototype approximately 2.2 km depth × 2.8 km × 3.0 km in dimensions.
The effect of H2O and CO2 on planetary mantles
Authors: Wyllie Peter J.
Published: February 2008

The solidus for peridotite‐H2O‐CO2 is a divariant surface traversed by univariant lines that locate the intersections of subsolidus divariant surfaces for carbonation or hydration reactions occurring in the presence of H2O‐CO2 mixtures. Vapor phase compositions are normally buffered to these lines; the buffering capacity of carbonates is much greater than that of amphibole and phlogopite. Near the buffered curve for the solidus of partly carbonated peridotite, extending to higher pressures and lower temperatures from an invariant point near 26 kb‐1200°C, there is a temperature maximum on the peridotite‐vapor solidus. On the CO2 side of the maximum, above 26 kb, CO2/H2O is greater in liquid than in vapor, and liquids are SiO2‐poor; on the H2O side of this maximum (including all pressures below 26 kb), H2O/CO2 is greater in liquid than in vapor, and liquids change from forsterite‐normative to quartz‐normative with increasing H2O/CO2 in vapor. Even traces of H2O and CO2, in minerals or vapor, lower mantle solidus temperatures through hundreds of degrees compared with the volatile‐free solidus.
Investigation of the stress‐concentration mechanism for intraplate earthquakes
Authors: Campbell David L.
Published: February 2008

The hypothesis is examined that concentrations of regional stress in or near mafic intrusions in the felsic continental plate may cause nearby seismicity. If the intrusions are stiffer than the plate, stress concentrations of only 20 or 30 percent above regional values are likely, but intrusions which have been weakened (as by serpentinization) may concentrate stresses more than 200 percent above the regional values. Pockets of seismicity may then occur in the continental plate near the intrusive.
Hawaiian Ridge seismicity from the Makapuu ocean bottom seismograph
Authors: Estill Robert E. , Odegard Mark E.
Published: February 2008

The Makapuu Ocean Bottom Seismograph, located 10 km off the southeast coast of Oahu in the Hawaiian Islands, recorded 359 events from July 30, 1976 to March 30, 1977. Sixty‐five epicenter locations indicate that most of these events are Hawaii Island activity; however, events apparently unrelated to Hawaii Island volcanic activity occur near the Hawaiian Ridge including: (1) an unusual event near Niihau Island (ML > 4.0); (2) three events (ML≅3‐3.5) near Maui and Kahoolawe islands indicating active faulting or perhaps extension of rift zones; (3) events south of the Hawaii Island, several corresponding to seamounts with historical seismic activity that may be related to submarine volcanism and associated periods of slumping and readjustment; (4) an offshore earthquake northeast of Oahu (ML ∼ 4.0) that was felt along the coast of the island. About 40% of the events not associated with Hawaii Island were undetected by land‐based stations. This study indicates that the Hawaiian Ridge may be more seismically active than previously thought.
Surface waves and low frequency noise in the deep ocean
Authors: Larsen Lawrence H.
Published: February 2008

Low frequency (1‐5 minute) pressure fluctuations have been observed in the deep sea beneath 4000 m of water. This paper proposes a model connecting the beat of surface gravity waves to the observed pressure fluctuations. The model depends on the presence of nonlinear surface gravity wave packets.
A study of the energetics of a particular Sun‐weather relation
Authors: Williams R. Gareth
Published: February 2008

The four components of the Lorenz energy cycle are analyzed by a superposed epoch method using as key dates the crossings by the earth of the solar sector boundaries in the interplanetary magnetic field. The eddy kinetic energy is expected to be related to the vorticity area index (VAI), which apparently exhibits a significant dependence on solar activity. Thus, the Lorenz energy cycle provides us with a means of attempting to establish a broader, physical picture of the atmospheric processes involved in solar modulation of the VAI. Seemingly significant results (> 95%) are obtained during the winter months; in particular, the eddy kinetic energy displays a response (∼ 97% at 500 mb) which is similar in nature to but of lesser amplitude and statistical significance than the VAI response. However, a "control experiment" utilizing random key dates suggests that the statistical significance of these results is actually much less. It is, therefore, concluded that no compelling evidence for a solar modulation of tropospheric energetics is found.
The response of atmospheric and lower ionospheric layer structures to gravity waves
Authors: Chiu Y. T. , Ching B. K.
Published: February 2008

We solve the linear problem of the density response of a neutral or ionospheric layer structure of arbitrary density profile to gravity wave perturbations in the background atmosphere. It is shown that the density response of the bottomside of the structure is of larger amplitude than the topside, whereas the general magnitude of the density response depends on the relative sharpness of the layer density gradient in comparison to the gradient of the quiescent background atmosphere. The sharper the layer gradient, the larger the layer density response. Interpretation and application of our results to the ozone and atomic oxygen layers, the sporadic‐E layer and to the D and E regions of the ionosphere are discussed.
Barotropic instability in the upper atmosphere of Venus
Authors: Elson Lee S.
Published: February 2008

Using a barotropic model, the upper atmosphere of Venus is examined for stability to small perturbations of a mean zonal wind. Several assumed mean zonal wind profiles, compatible with Mariner 10 UV observations, are examined with the result that some are stable, while others are unstable. At least one of the unstable profiles exhibits a maximum in the growth rate for wave‐number 3, in agreement with some UV observations of the clouds of Venus. The barotropic model should be useful for performing instability analyses using Pioneer Venus data in 1979.
Estimates on the production of CO and H2 from the oxidation of hydrocarbon emissions from vegetation
Authors: Zimmerman Patrick R. , Chatfield Robert B. , Fishman Jack , Crutzen Paul J. , Hanst Phillip L.
Published: February 2008

Extrapolating from extensive field measurements on foliar emissions in the U. S. we arrive at approximate global inputs of isoprene and terpenes of 3.5 × 1014 and 4.8 × 1014 g(C)/yr respectively. The oxidation of these hydrocarbons could contribute in an important way to the atmospheric sources of CO (4.2− 13.3 × 1014g/yr)and H2 (10 − 35 × 1012g/yr), and to organic species soluble in rainwater.
The reaction Cl + H2CO→ HCl + HCO: Decreased sensitivity of stratospheric ozone to chlorine perturbations
Authors: Stief L. J. , Michael J. V. , Payne W. A. , Nava D. F. , Butler D. M. , Stolarski R. S.
Published: February 2008

The absolute rate constant for the reaction Cl + H2CO → HCl + HCO has been determined by the flash‐photolysis‐resonance fluorescence method to be 7.5 ± 0.9 (2σ) × 10−11 cm³ molecule−1 sec−1 at 298K and to have a negligible temperature dependence. This rate which at stratospheric temperatures is more than 2000 times faster than the rate of Cl + CH4 and more than a factor of 2 faster than Cl + HO2, indicates that formaldehyde (H2CO) will compete significantly with methane (CH4) and HO2 for the conversion of active chlorine in the stratosphere to the inactive reservoir HCl. Chlorine will thus be a less efficient destroyer of stratospheric ozone than previously believed. One‐dimensional eddy‐diffusion photochemical model calculations indicate that the eventual ozone depletion for a steady‐state CFM release at 1975 rates (750,000 tons/year) will be lowered from 20% to 18.5% by the inclusion of this reaction.
Phobos: Photometry and origin of dark markings on crater floors
Authors: Goguen J. , Veverka J. , Thomas P. , Duxbury T.
Published: February 2008

Viking Orbiter 1 close encounter pictures of Phobos reveal unusual dark patches on the floors of many craters. Photometry of these features indicates that they have a similar normal reflectance but a phase coefficient 30% larger than the average surface. These facts suggest that the "dark" material has a similar composition but a much rougher texture than the average surface of Phobos. By analogy with terrestrial impact, explosion and laboratory craters, the dark patches are interpreted as impact generated melt pools which remain visible on Phobos due to the low value of g and consequent small amount of fallback ejecta and slumping. Since blanketing by ejecta from subsequent impacts and micrometeoroid erosion should eventually obliterate such features, they should be more conspicuous in the fresher craters. Similar features should be visible on small asteroids and other low g bodies. However, they are not prominent on the surface of Deimos—possibly because most of the craters imaged at high resolution on the outer satellite appear to have been blanketed by several meters of fine‐grained material.
Comment on ion and electron temperatures in the Martian upper atmosphere
Authors: Johnson R. E.
Published: February 2008

Ion temperature profiles measured by the retarding potential analyzers on Viking I and II are examined. It is found that the thermal conduction must be modified by other transport processes or by the presence of magnetic fields to account for the observed profiles. Such processes also effect the electron temperature profile, which, however, was not measured. Estimates of the magnetic field parameters are obtained assuming the magnetic field is the dominant effect.
Stratospheric measurements of methane at several latitudes
Authors: Bush Y. A. , Schmeltekopf A. L. , Fehsenfeld F. C. , Albritton D. L. , McAfee J. R. , Goldan P. D. , Ferguson E. E.
Published: February 2008

Samples of stratospheric air were obtained at altitudes up to about 35 km from balloon flights carried out at 4°S (Brazil), 78°S (Antarctica), and 41°N (two flights, Wyoming) in 1978. The samples obtained were analyzed for methane using a gas Chromatograph with flame ionization detection. The two Wyoming profiles and the Antarctica profile are similar. However, the Brazil profile, which is the first low‐latitude stratospheric‐methane profile reported, falls off much less rapidly with altitude, even when reduced to a common tropopause reference. The use of these methane profiles to deduce OH profiles is explored.
Determination of the geocentric gravitational constant from laser ranging on near‐Earth satellites
Authors: Lerch Francis J. , Laubscher Roy E. , Klosko Steven M. , Smith David E. , Kolenkiewicz Ronald , Putney Barbara H. , Marsh James G. , Brownd Joseph E.
Published: February 2008

Laser range observations taken on the near‐earth satellites of Lageos (a = 1.92 e.r.), Starlette (a = 1.15 e.r.), BE‐C (a = 1.18 e.r.) and Geos‐3 (a = 1.13 e.r.), have been combined to determine an improved value of the geocentric gravitational constant (GM). The value of GM is 398600.61 km³/sec², based upon a speed of light, c, of 299792.5 km/sec. Using the IAG adopted value of c equalling 299792.458 km/sec scales GM to 398600.44 km³/sec². The uncertainty in this value is assessed to be ± .02 km³/sec². Determinations of GM from the data taken on these four satellites individually show variations of only .04 km³/sec² from the combined result.

The Lageos information dominated the combined solution, and gave the most consistent results in its data subset solutions. The value obtained for GM from near‐earth laser ranging compares quite favorably with the most recent results of the lunar laser and interplanetary experiments.
Electron flux and auroral intensity measurements in situ
Authors: McEwen D. J. , Venkatarangan P.
Published: February 2008

A rocket (ADD‐II‐128) launched into bright aurora at Churchill, Canada on February 21, 1974 provided in situ measurements of electron influx and resulting 5577A emission intensity. The rocket descended through a broad and fairly homogeneous arc of 70 kR intensity. Measurements of downward electron energy flux (18 keV‐20 eV) at the rocket during the time it descended from 120 to 110 km were compared with resulting emission intensities directly below the rocket. They yielded excitation efficiencies of 0.67 kR of 5577A OI and 180R of 4278A N2+ per erg/cm² sec energy influx. These values agree well with calculated values for bright auroras.
Stress memory of crystalline rocks in acoustic emission
Authors: Kurita Kei , Fujii Naoyuki
Published: February 2008

In acoustic emission studies on granite under uniaxial compression, clear hysteresis of emission numbers related to the stress history (Kaiser effect) was observed below dilatancy onset stress. The maximum stress loaded in the past is memorized in rocks. Above dilatancy, we could not observe such a hysteresis. These features are explained by the nature of irreversible sudden advances of microcrack tips. Recovery process time of this hysteresis is over one month under room humidity and temperature conditions. The results in this paper cast foundation for the applicability of geostress measurements by the acoustic emission method.
High pressure phase transformations in MgF2 (rutile)
Authors: Ming Li‐chung , Manghnana Murli H.
Published: February 2008

Employing a diamond‐anvil pressure cell and a YAG laser as a heating source, phase relationships in polycrystalline MgF2 (rutile) were investigated to ∼330 kbar at both room temperature (∼23°C), and high temperature (∼1300°C). In situ high pressure X‐ray diffraction data show that MgF2 (I) of rutile structure transforms into MgF2(II) of a cubic structure at ∼300 kbar at room temperature, and at ∼190 kbar at high temperature (∼1300°C), resulting in a negative dP/dT slope for the univariant line between MgF2(I) and MgF2(II) in the P‐T phase diagram. The molar volume differences at room temperature between MgF2(I) and MgF2(II) at 190 kbar and 300 kbar are ∼8% and ∼5%, respectively.
Cause and effect in some types of Sun‐ weather‐ relationship
Authors: Volland Hans , Schaefer Josef
Published: February 2008

It is shown that the quasi 27 day periodicity of the height of the 500 mbar level detected by King and related by him to the rotating sun consists of real persistent planetary waves within the spectral band with periods between 25 and 30 days. These waves have life‐times of several months to one year and seem to be randomly generated by internal turbulent processes within the troposphere without any trigger mechanism from outside the atmosphere. On the other hand, the sector structure of the interplanetary magnetic field as well as the grouping of sunspots on preferred active longitudes rotate nearly rigidly with the sun with periods between about 26 and 28 days. The lifetimes of these structures range also between months and years. It is concluded that this accidential coincidence of two independent persistent turbulent processes possessing similar periods and similar lifetimes gives the illusion of a physical connection (‘sun‐weather‐ effect’) which in fact does not exist.
Nighttime ionization by energetic particles at Wallops Island in the altitude region 120 to 200 km
Authors: Voss H. D. , Smith L. G.
Published: February 2008

Five Nike Apache rockets, each including an energetic particle spectrometer and an electron density‐electron temperature experiment, have been launched from Wallops Island (L = 2.6) near midnight under varying geomagnetic conditions. On the most recent of these (5 January 1978) an additional spectrometer with a broom magnet, and a 391.4 nm photometer were flown. The data from this flight indicate that the energetic particle flux consists predominantly of protons, neutral hydrogen and possibly other energetic nuclei. The energy spectrum becomes much softer and the flux more intense with increasing Kp for 10<E<100 keV. The pitch angle distribution at 180 km is asymmetrical with a peak at 90° indicating that the majority of particles are near their mirroring altitude. Ionization rates are calculated based on the measured energy spectrum and mirror height distribution. The resulting ionization rate profile is found to be nearly constant with altitude in the region 120 to 200 km. The measured energetic particle flux and calculated ionization rate from the five flights are found to vary with magnetic activity (based on the Kp and Dst indexes) in the same way as the independently derived ionization rates deduced from the electron density profile.
Large amplitude substorm motion of the magnetotail boundary
Authors: Crooker N. U. , Siscoe G. L.
Published: February 2008

During a period of several days when the solar wind was relatively quiet, the magnetotail boundary near lunar distance swept back and forth past Explorer 33 as the spacecraft traveled through a distance perpendicular to the Earth‐sun line of about 17 Re. The boundary crossings are remarkably well‐correlated with peaks in the AE index, even though the magnitudes of the peaks are only on the order of 200 nT. Examination of the regions of multiple crossings on other Explorer 33 and 35 orbits reveals that they commonly cover large distances perpendicular to the Earth‐sun line, although correlation with AE is often obscured, probably by external solar wind conditions. We conclude that a substantial fraction of the scatter in published statistical plots of boundary crossing positions can be accounted for in terms of an internal substorm‐related motion with an amplitude of 5‐8 Re. The data suggest that the motion takes the form of a compressional deformation wave convecting down the tail.
Stratospheric chemistry: Multiple solutions
Authors: Prather M. J. , McElroy M. B. , Wofsy S. C. , Logan J. A.
Published: February 2008

It is shown that the equations describing chemical partitioning among Clx (HCl, Cl, ClO, ClNO3), NOt (NO, NO2, NO3, N2O5, HNO2, ClNO3) and HOx (OH, HO2) may admit multiple solutions. These solutions apply to the high latitude winter stratosphere where abrupt spatial variations may be expected for NO2, ClO and ClNO3.
High temperature olivine creep: Evidence for control by edge dislocations
Authors: Gueguen Yves
Published: February 2008

Dislocation microstructures in olivine grains from experimentally deformed specimens as well as from peridotite xenoliths in lavas indicate that (1) edge dislocations probably control the creep rate and (2) {110} planes exert a strong crystallographic control on b=[100] edge dislocations even at very high temperatures (0,9 Tm). This observation can be explained by a sessile splitting or by the existence of a deep Peierls valley in {110} planes. In either case, kink and jog nucleation are likely to be difficult so that creep can be controlled either by kink or jog formation. This interpretation implies that different activation energies should be associated with the different glide systems. It is in agreement with the fact that the activation energy for creep is not that for oxygen diffusion.
Tides and the midnight temperature anomaly in the thermosphere
Authors: Mayr H. G. , Harris I. , Spencer N. W. , Hedin A. E. , Wharton L. E. , Porter H. S. , Walker J. C. G. , Carlson H. C.
Published: February 2008

Spectral analysis of the midnight temperature anomaly observed on AE‐E indicates that the phenomenon can be adequately represented with wave numbers 1<m<5. Theoretical results from a multi‐constituent circulation model suggest that this feature and associated variations in composition are the result of a complex interaction between the semidiurnal tide generated in the lower atmosphere and ion‐neutral momentum coupling associated with the diurnal variation of the ion density which in turn also generates higher order tidal modes. The semidiurnal tide from the lower atmosphere and the ion drag induced component excited in the thermosphere are out of phase and of comparable magnitudes. Variability in the tidal excitation source and the prevailing wind system of the lower atmosphere as well as in the ionospheric density (which itself is sensitive to tide‐generated dynamo electric fields) are presumably responsible for the observed lability of the midnight temperature anomaly.
Voyager spacecraft radio observations of Jupiter: Initial cruise results
Authors: Kaiser M. L. , Desch M. D. , Riddle A. C. , Lecacheux A. , Pearce J. B. , Alexander J. K. , Warwick J. W. , Thieman J. R.
Published: February 2008

Jupiter's hectometric (HOM) wavelength radio emissions have been detected by the planetary radio astronomy instruments onboard the two Voyager spacecraft. The emission is surprisingly similar in morphology but opposite in polarization to the decametric (DAM) wavelength Jovian radio noise that has been observed with ground‐based telescopes for more than two decades. The HOM emissions are predominantly left‐hand polarized and their occurrence is modulated by the rotation phase of the planet but not by the location of the satellite Io. Several possible explanations for the behavior of the HOM emission are examined, but none of them are completely satisfactory.
Whistlers observed by Voyager 1: Detection of lightning on Jupiter
Authors: Gurnett D. A. , Shaw R. R. , Anderson R. R. , Kurth W. S. , Scarf F. L.
Published: February 2008

During the Voyager 1 encounter with Jupiter a number of discrete signals were identified in the wideband plasma wave data with characteristics similar to whistlers generated by lightning. In this paper we show that the calculated whistler‐mode travel times from Jupiter to the spacecraft are in good agreement with the measured dispersion characteristics, thereby confirming that the signals are caused by lightning on Jupiter and substantiating the Voyager 1 photographic evidence for lightning on Jupiter. A quantitative estimate of the north‐south thickness of the Io plasma torus is also obtained from the measured whistler dispersion.
Preliminary observations of lightning radar echoes and simultaneous electric field changes
Authors: Szymanski Edwin W. , Rust W. David
Published: February 2008

Measurements of radar echoes from lightning discharges within intense thunderstorms in Oklahoma have been made with a 10 cm Doppler radar. Also measured was the electric field change associated with the lightning. The lightning echoes were analyzed by displaying echo intensity at a particular range versus time. Temporal comparisons could then be made with the electric field changes. Radar echoes were detected from both intracloud and cloud‐to‐ground discharges. Relatively abrupt increases in lightning radar echo intensity sometimes appeared related to the occurrence of return strokes, K‐type electric field changes, and during continuing currents. The radar antenna beam width was 0.8°, and we undoubtedly often did not receive echoes from the entire discharge process during any given lightning flash. Lightning echoes were detected at ranges of 30‐180 km and at altitudes of 0.8‐9.8 km in regions of storms with reflectivity factors of up to 58 dBz. Lightning echoes were 10‐25 dB stronger than the precipitation echo in which they occurred, and they generally were observed in regions where the precipitation echo was less than the maximum for the storm. The mean duration of the observed lightning echoes is 342 ms with a standard deviation of 270 ms. The longest spatial extent of a lightning echo that we observed was 45 km.
N2O and CO production by electric discharge: Atmospheric implications
Authors: Levine Joel S. , Hughes Ron E. , Chameides William L. , Howell William E.
Published: February 2008

Enhanced levels of N2O and CO were measured in tropospheric air samples exposed to a 17.5 × 10³ joule laboratory discharge. These enhanced levels correspond to an N2O production rate of about 4 × 1012 molecules joule−1 and a CO production rate of about 1 × 1014 molecules joule−1. The CO measurements suggest that the primary region of chemical production in the discharge is the shocked air surrounding the lightning channel, as opposed to the slower‐cooling inner core. Additional experiments in a simulated Venus atmosphere (CO2 ‐ 95%, N2 ‐ 5%, at one atmosphere) indicate an enhancement of CO from less than 0.1 ppm prior to the laboratory discharge to more than 2000 ppm after the discharge. Comparison with theoretical calculations appears to confirm the ability of a shock wave/thermochemical model to predict the rate of production of trace species by an electrical discharge.
Atmospheric spectra and the temperature dependence of collisional cross sections
Authors: Miziolek Andrzej W.
Published: February 2008

Recent experimental results indicate that the collision cross sections between infrared‐absorbing molecules and non‐absorbing colliding partners exhibit considerable temperature dependence in the atmospheric temperature range. This dependence has to be taken into account when deconvoluting solar spectra into molecular mixing ratios. On the basis of experimental results for the HCl‐Ar system, a simple calculation is made to assess the magnitude of this effect for HCl‐air. The calculated temperature effect is found to be small (approximately 4 percent). However, conditions where this effect is much larger and more significant are discussed. The direction of the effect is clear. The increasing cross sections (with decreasing temperatures) lead to smaller deduced concentrations. Since this is potentially a significant correction affecting not only the absolute magnitude of mixing ratios but also the altitude profiles of HCl and other key atmospheric components, it is suggested that the definitive experiments be carried out for the various atmospheric broadening systems.
Observations of details of hysteresis loops in westerly granite
Authors: Peselnick L. , Liu Hsi‐Ping , Harper K. R.
Published: February 2008

Capacitive‐displacement transducers were used in an apparatus designed to measure the specific dissipation constant Q‐1 and to determine the details of the shape of stress‐strain hysteresis loops for rocks. For room‐dry Westerly Granite at room temperature and pressurehysteresis loops were recorded for cyclic strains having amplitudes between 0.6 × 10−6 to 0.5 × 10−5 at a period of 5 seconds. Two types of wave forms were used: a quasisinusoid at the lower strains and a distorted sinusoid having flattened peaks at the larger strains. Loops having sharp corners or cusps reported in the literature were not observed. The measured QE (for the Young's modulus mode) at 0.2 Hz and 10−6 strain amplitude was 87± 7.
Energetic oxygen: A direct coupling mechanism between the magnetosphere and thermosphere
Authors: Torr Marsha R. , Torr D. G.
Published: February 2008

This study investigates the effects of the precipitation of energetic O+ ions (0.7 – 12 keV) into the atmosphere during magnetic storms. The energetic O+ ion flux produces a splash of lower energy neutral oxygen atoms at the top of the atmosphere. As a result of the photo‐ionization and charge exchange with H+ ions in the plasmaspherethese backscattered atoms produce a low energy O+ flux that is more than 10 times larger in magnitude than the original energetic O+ flux. The energetic O+ events thus provide a potential source mechanism for the lower energy (≲30 eV) O+ ions observed in the plasmasphere. We also suggest that the energetic ion events may be self‐sustaining in that some of the ionized ‘splash’ particles (≲10%) are subsequently accelerated by an as yet unidentified mechanism to the higher observed energies. We find that 96% of the incoming energy is transferred to the neutral atmosphere in the form of heating. Measured fluxes indicate heating rates as high as ∼0.4 ergs cm−2sec−1ster−1.
The concentration of atomic oxygen in the auroral lower thermosphere
Authors: Torr D. G. , Sharp W. E.
Published: February 2008

A method is described to determine the concentration of atomic oxygen in the altitude range 100 to 160 km in an aurora from the ratio of the volume emission rates of the O(¹S) 5577Å to N2+ in 3914Å emissions. Applying the technique to previously published measurements it is found that the O density at 100 km is typically about 1 × 1011cm−3. The occurrence of densities in excess of 2 × 1011cm−3 in the aurora at 100 km is rare.
On the spatial relationship of 1‐meter equatorial spread‐F irregularities and depletions in total electron content
Authors: Tsunoda Roland T. , Towle David M.
Published: February 2008

An experiment was conducted at Kwajalein AtollMarshall Islands to investigate the spatial relationship of 1‐m equatorial spread‐F irregularities to total electron content (TEC) depletions. A high‐power radar was operated (1) in a backscatter scan mode to spatially map the distribution of 1‐m irregularitiesand (2) in a dual‐frequencysatellite‐track mode to obtain the longitudinal TEC variations. We show that radar backscatter “plumes” found in the disturbednighttime equatorial ionosphere are longitudinally coincident with TEC depletions. We suggest that the TEC depletions are probably due to the presence of plasma “bubbles” in the equatorial F layer.
Measurements of wind vectors, eddy momentum transports, and energy conversions in Jupiter's atmosphere from Voyager 1 images
Authors: Beebe Reta F. , Ingersoll Andrew P. , Hunt Garry E. , Mitchell Jim L. , Müller Jan‐Peter
Published: February 2008

Voyager 1 narrow‐angle images were used to obtain displacements of features down to 100‐200 km in size over intervals of ten hours on February 26‐27, 1979. A global map of velocity vectors and longitudinally‐averaged zonal wind as functions of latitude are presented. Denoting departures of the zonal and meridional wind from their longitudinal means by u′ and v′, respectively, the velocity correlation and the meridional gradient d/dy are compared as functions of latitude. A weak but statistically significant positive correlation is found. The implied rate of conversion from eddy kinetic energy to zonal mean kinetic energy is large and may be comparable to the fluxes of solar and internal energy.
Shock temperature measurements in Mg2SiO4 and SiO2 at high pressures
Authors: Lyzenga Gregory A. , Ahrens Thomas J.
Published: February 2008

Temperatures in the high pressure shock state have been determined by measurement of optical radiation from pure samples of forsterite (Mg2SiO4), α—quartz, and fused silica. Shock waves of known amplitude were produced by tantalum flyer impact using a two‐stage light gas gun. Shock pressures in the ranges 150‐175 GPa and 70‐115 GPa for Mg2SiO4 and SiO2 respectively were achieved, and temperatures in the range 4500‐6800 K were measured. The observed temperatures in Mg2SiO4 are consistent with the occurrence of a shock‐induced phase transition with a transition energy of ∼ 1.5 MJ/kg. Measured Hugoniot temperatures versus pressure in both fused and crystalline SiO2 shocked to the stishovite regime suggest the occurrence of a previously unknown transition, beginning at pressures of approximately 107 GPa and 70 GPa for α—quartz and fused quartz, respectively. The energies and temperatures appear to be consistent with the onset of melting of stishovite under shock loading.
An average parallel electric field deduced from the latitude and altitude variations of the perpendicular electric field below 8000 kilometers
Authors: Mozer F. S. , Torbert R. B.
Published: February 2008

The average equatorward component of the perpendicular electric field between the dusk plasmapause and polar cap has been determined at seven altitudes below 8000 kilometers by averaging large scale electric field measurements made on 166 passes of the S3‐3 satellite through the dusk auroral zone. The observed variation of the perpendicular electric field with altitude and latitude requires the presence of an upward pointing parallel electric field over a latitude range of a few degrees centered near 70° invariant latitude, and with a maximum parallel potential of several kilovolts.
The influence of NO and CℓO variations at twilight on the interpretation of solar occultation measurements
Authors: Boughner Robert , Larsen Jack C. , Natarajan Murali
Published: February 2008

Measurement of short‐lived photochemically‐produced species in the stratosphere by solar occultation is difficult because the rapid variation of such species near the terminator introduces ambiguities in interpreting the measured absorption in terms of meaningful atmospheric abundances. These variations produce tangent path concentrations that are asymmetric relative to the tangent point, as opposed to the symmetrical distribution usually assumed in most inversion algorithms. Neglect of this asymmetry may yield an inverted profile that deviates significantly from the true sunset/sunrise profile. In the present paper, the influence of this effect on solar occultation measurements of CℓO and NO is examined. Time varying altitude profiles of CℓO and NO were calculated with a time‐dependent photochemical model to simulate the distribution of these species during a solar occultation measurement. These distributions were subsequently used to calculate simulated radiances for various tangent paths from which mixing ratios were inferred with a conventional technique that assumes spherical symmetry. These results show that neglecting the variation of CℓO in the retrieval process produces less than a 10 percent error between the true and inverted profile for both sunrise and sunset above 18 km. For NO, errors are less than 10 percent for tangent altitudes above about 35 km for sunrise and sunset; at lower altitudes, the error increases, approaching 100 percent at altitudes near 25 km. The results also show that average inhomogeneity factors, which measure the concentration variation along the tangent path and which can be calculated from a photochemical model, can indicate which species require more careful data analysis.
Long‐term 1.5 GHz amplitude scintillation measurements at the magnetic equator
Authors: Basu Sunanda , Basu Santimay , Mullen John P. , Bushby A.
Published: February 2008

The diurnal and seasonal behavior of long‐term (approximately 20 months) 1.54 GHz amplitude scintillation measurements under low sunspot conditions observed at Huancayo, Peru are presented. The measurements refer to a low elevation geometry in the E‐W plane at the magnetic equator. The data show clear equinoctial maxima of occurrence and confinement to the pre‐midnight hours. There is a total absence of scintillations during the May‐July period.

The present results are critically compared to previously reported GHz measurements in the context of geometry of observations, equatorial irregularity strength variation and spatial structure information obtained from in‐situ data.
Geomagnetic excursion in late‐glacial basalt outcrops in south‐western Iceland
Authors: Kristjansson Leo , Gudmundsson Agust
Published: February 2008

Three hills in the active volcanic zone of the Reykjanes peninsula, SW‐Iceland, are largely composed of volcanic tuffs and thin lava flows having stable, shallow reverse directions of magnetization. These hills are most probably contemporaneous and of late Wisconsinan age. Their mean virtual pole position is at 254°E, 12°S. Along with a geomagnetic event of similar age recently discovered elsewhere in SW‐Iceland, this excursion may define a useful stratigraphic horizon in studies of the Mid‐Atlantic ridge crest in Iceland.
Pulsating aurora: The importance of the ionosphere
Authors: Stenbaek‐Nielsen H. C.
Published: February 2008

A number of different, but mainly optical, observations made in pulsating auroras are presented. These observations indicate that active ionospheric processes are likely to play an important role in causing and/or modifying pulsating aurora.
Laboratory measurements of the O+(²D) + N2 and O+(²D) + O2 reaction rate coefficients and their ionospheric implications
Authors: Johnsen Rainer , Biondi Manfred A.
Published: February 2008

Rate coefficients have been measured at thermal energies for the charge transfer reactions of metastable O+(²D) ions with N2 and O2. At an effective temperature of ∼ 550 K we find k(N2) = (8 ± 2) × 10−10 cm³/sec and k(O2) = (7±2) × 10−10 cm³/sec. These drift tube‐mass spectrometer measurements employ the reaction He+ + O2 as the source of the metastable O+ ions, and evidence is presented that the ions thus produced are in the ²D state rather than the ²P state, a possible alternative identification. The O+(²D) + N2 charge transfer rate is considerably larger than that deduced in existing photochemical model analyses of Atmosphere Explorer observations. Some of the ionospheric implications of the laboratory measurements are discussed.