bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical properties of the ash from El Chichon Volcano
Authors: Patterson E. M. , Pollard C. O. , Galindo I.
Published: February 2008

We have measured visible wavelength optical properties of the ash from the 1982 El Chichón eruptions. These measurements were made on ash samples collected at three surface sites at distances between 12 and 80 km from the volcano. The most distant sample is taken as most representative of the silicate ash injected into the stratosphere.

The measured optical properties are expressed as a complex refractive index n, with the aerosol absorption expressed as the imaginary component of the refractive index, nIM. Each of these samples showed quite low values of absorption, with nIMat 500 nm ranging from 1.5×10−3for the 12 km sample to 1.0×10−3for the 80 km sample. Based on these measurements, we estimate that n for the stratospheric silicate ash is given by n = 1.53 ‐ 0.001i.
Short wavelength stabilization of the gradient drift instability due to velocity shear
Authors: Huba J. D. , Lee L. C.
Published: February 2008

A nonlocal analysis of the gradient drift instability is presented. The new effect included in this theory is the allowance for an inhomogeneous electric field which produces a sheared drift velocity. It is found that velocity shear can stabilize the short wavelength modes of the instability, and preferentially excite a longer wavelength mode than would be expected based upon local theory. This result may explain the observations of dominant, long wavelength irregularities in the equatorial electrojet [Kudeki et al., 1982; Pfaff et al., 1982] and be relevant to the formation of auroral arc elements.
The supersaturation of carbonyl sulfide in surface waters of the Pacific Ocean off Peru
Authors: Ferek Ronald J. , Andreae Meinrat O.
Published: February 2008

Carbonyl sulfide (COS) was found to be supersaturated by a factor averaging 2.6 with respect to the atmosphere in surface waters of the continental shelf of Peru. The degree of supersaturation was correlated with dissolved dimethyl sulfide (DMS) concentrations indicating a possible biogenic source of atmospheric COS. The oceanic source of COS could account for a substantial fraction of the COS flux to the atmosphere.
The relationship of total Birkeland currents to the merging electric field
Authors: Bythrow P. F. , Potemra T. A.
Published: February 2008

The sun‐synchronous orbit of the MAGSAT spacecraft has provided us with a new means to study the temporal response of large‐scale Birkeland currents to variations in interplanetary parameters. We examined magnetic field data from 32 MAGSAT crossings of the northern auroral zone selected from 6 days in November and December, 1979. On each day at least 5 consecutive orbits were studied.

The objectives of this study were to examine variations in the gross features of magnetic field disturbances observed on consecutive MAGSAT orbits, to investigate their relationship to interplanetary quantities, to estimate the total Birkeland current magnitude and correlate this current with various IMF parameters, and to study the relationship between the total Birkeland current and the inferred merging electric field EM. Inspired by recent calculations (Siscoe, 1982; Cornwall, 1982) a total Birkeland current (Itot) versus EM relationship was deduced. The results of our study indicate the following: (1) On an orbit‐to‐orbit basis, the most marked variation in the characteristics of the magnetic field disturbance was observed in amplitude rather than latitudinal width or location. (2) There is a consistently high correlation R ∼ 0.80 between either the observed average magnetic field disturbance ΔB or Itot and various IMF parameters, with the highest correlation coefficient (0.82) for Itot vs VB sin² θ/2. (3) The fit of Itot vs EM allows us to estimate a total auroral zone conductance of ∼18.7 mho. (4) The functional relation Itot = A(EM)p + B provided a good fit between Itot and EM for values of p ranging from 0.5 to 2.5, with the best fit for p = 1.0 to 5/3.
On the extraction of tidal information from measurements covering a fraction of a day
Authors: Crary David J. , Forbes Jeffrey M.
Published: February 2008

The errors incurred by extracting tidal information from data covering only a fraction of a day are investigated quantitatively as a function of fit span and tidal period. Assuming a noise component in the observational data with standard deviation σ, errors in the diurnal and semidiurnal Fourier components equal to σ occur at fit spans of 15.5 and 13.5 hours, respectively, for hourly data points. Errors increase at an exponential rate for shorter fit spans. Assuming nominal values of tidal amplitudes and standard deviations applicable to 12 hours of daytime mesopause region winds that might be obtained from MST radar measurements, it is shown that data is required at approximately 5‐minute intervals to determine with acceptable accuracy tidal Fourier components from a single day's measurements. Alternatively, one to three weeks of daytime data at 30‐minute intervals would enable determination of diurnal and semidiurnal components to roughly the same accuracy.
Ion acceleration in the suprauroral region: A Monte Carlo Model
Authors: Retterer John M. , Chang T. , Jasperse J. R.
Published: February 2008

The acceleration of ions and the formation of ion conics in the suprauroral region is studied using a model which includes the effects of wave‐particle interaction, the inhomogeneous geomagnetic field, and field‐aligned potential drops. Particle acceleration by interaction with turbulence is treated as a random process in a simplified way using a Monte Carlo technique. Applying the model to ion acceleration by lower‐hybrid turbulence between 1000 and 5000 km, we find that the observed amplitudes of the waves are sufficient to accelerate ions to the energies often found in conics.
Late Cretaceous apparent polar wander of the Pacific Plate: Evidence for a rapid shift of the Pacific hotspots with respect to the spin axis
Authors: Gordon Richard G.
Published: February 2008

Paleomagnetic data from the Pacific plate show that the average azimuth of the Pacific plate decreased by ∼12° between 90 Ma and 81 Ma, whereas trends of Late Cretaceous seamount chains suggest that the Pacific plate moved northwestward relative to the hotspots with little change in azimuth during the same time interval. This difference is used to infer a 13°±4° shift of the spin axis relative to the hotspots in the Pacific Ocean basin. This shift occurred within 5 m.y. of the occurrence of anomalous behavior of the paleomagnetic field recorded in anomalies 33 and 34. This coincidence in timing suggests there may be a causal link between these three phenomena.
Comparison of spherical double probe electric field measurements with plasma bulk flows in plasmas having densities less than 1 cm−3
Authors: Mozer F. S. , Hones E. W. , Birn J.
Published: February 2008

Point‐by‐point comparisons of ISEE‐1 spherical double probe dawn‐to‐dusk electric field measurements and ISEE‐2 plasma flows, converted to electric fields, are presented during a three hour time interval in the magnetotail when the plasma density varied from less than 0.1 to about 1 cm−3. The zero lag cross‐correlation coefficient between 768 second averages of the two data sets was 0.93. The cross‐correlation coefficient decreased with shorter averaging intervals due to the increasing magnitude of statistical uncertainties, becoming 0.49 for 9 second averages. A statistical relative uncertainty between pairs of points in the two data sets, estimated by inclusion only of counting statistics in the plasma measurement and time variations of the observed electric field during the measurement interval, is able to account for at least 75% of the deviations between the two data sets. During this three hour interval, the spacecraft potential (measured by the double probe instrument) varied as the logarithm of the product of the plasma density and square root of electron temperature (measured by the fast plasma analyzer), in agreement with expectations from simple Langmuir probe theory.
Equatorial ionospheric currents derived from MAGSAT data
Authors: Roy Manashi
Published: February 2008

The MAGSAT data on the three components of the geomagnetic field are subjected to ring current correction and crustal anomaly elimination near the dip equator. The evidence of a strong west east electrojet current below the satellite height (∼ 350 km) is confirmed. Strong evidence of east west component of the field suggests the existence of a vertical current originating at the jet level and extending upwards. A model calculation shows that such a current system can explain the satellite data as well as the ground data.
Regolith Breccia Allan Hills A81005: Evidence of lunar origin, and petrography of pristine and nonpristine clasts
Authors: Warren Paul H. , Taylor G. Jeffrey , Keil Klaus
Published: February 2008

MnO/FeO ratios in pyroxene, texture (abundant brown, swirly glass, in general typical of lunar regolith breccias), and overall composition (∼75% plagioclase) all indicate that Allan Hills A81005 is of lunar origin. It is presumably from a heretofore unsampled region of the Moon. It differs in detail from other regolith samples, e.g., it has exceptionally low contents of Na and KREEP. A pristine clast contains exceptionally coarse augite, compared to similar Apollo samples. ALHA81005 is not perceptibly more shocked than typical Apollo regolith breccias. Therefore, its discovery on Earth lends further credence to suggestions that SNC achondrites were derived by impact ejection from Mars.
Petrology of ALHA81005, the first lunar meteorite
Authors: Simon S. B. , Papike J. J. , Shearer C. K.
Published: February 2008

Petrography and mineral compositions show that ALHA81005 is a lunar highland regolith breccia and is the first known lunar meteorite. Lithic clasts are abundant and most are members of the anorthosite‐norite‐troctolite highland suite. Plagioclase compositions in lithic clasts and single grains are calcic (An94‐98). Pyroxene compositions, Al‐Ti and MnO‐FeO relationships support a lunar highland origin. A non‐KREEPy source region is indicated, and the unexplored far side of the moon cannot be ruled out as a potential source.
ALHA 81005: Moon, mars, petrography, and Giordano Bruno
Authors: Ryder Graham , Ostertag Rolf
Published: February 2008

Meteorite ALHA 81005, a glassy regolith breccia, is beyond any reasonable doubt of lunar origin, according to its petrographic, chemical, and isotopic characteristics. The sample was shocked at most to 15 GPa during ejection and supports the possibility of some meteorites being of Martian origin. Most lithic fragments are feldspathic granulitic impactites, cataclastic anorthosites, and impact melts, all typical lunar lithologies. Mineral fragments are derived from plutonic troctolitic and noritic rocks, varied mare basalt‐like extrusive rocks, and the identified lithic fragment types. Neither petrographically nor chemically are there significant components in ALHA 81005 which were previously unknown. A mare basalt component restricts the origin of the sample: with remotely‐sensed data, which eliminates most frontside, as well as farside groundtrack regions, it makes the probability of ejection from Giordano Bruno, near the Moon's NE limb, far greater than from any other lunar crater.
Thermoluminescence and nuclear Particle tracks in ALHA‐81005: Evidence for a brief transit time
Authors: Sutton S. R. , Crozaz G.
Published: February 2008

Thermoluminescence and nuclear particle track measurements were made on the Antarctic meteorite ALHA‐81005. No nuclear particle tracks were found in lithic fragments indicating that the clast material never resided at the very surface of the parent body. The unusually low natural thermoluminescence of this material is interpreted as being due to a combination of anomalous fading and thermal decay. The thermal decay could be due to very long terrestrial age or heating either during atmospheric entry, in a near sun orbit or during a parent body impact event. Impact heating is considered the more likely of these possibilities for this meteorite. If the impact heating interpretation is correct the thermoluminescence data constrains the space exposure time of the object to be less than 2,500 years. Such a brief Earth transit time is consistent with a lunar origin for this meteorite.
Possible lunar source areas of meteorite ALHA81005: Geochemical remote sensing information
Authors: Pieters Carle M. , Hawke B. Ray , Gaffey Michael , McFadden Lucy A.
Published: February 2008

Antartic meteorite ALHA81005 is a regolith breccia apparently sent to earth by an impact event in the lunar highlands. Laboratory studies of this sample provide information that is used to understand the source region on the moon using remote sensing data. The meteorites' low Thorium content is inconsistent with Thorium values measured for the central lunar nearside from orbit with Apollo γ‐ray spectrometers. Similarly, the mineral assemblages inferred from near infrared spectra of small impact craters on the lunar nearside do not exhibit the significant component of olivine and Fe‐bearing feldspar that is observed in the meteorite spectra. The existing remote sensing data suggest the most probable source region for ALHA81005 is the nearside limb or the lunar farside and that the composition of ALHA81005 represents a surface unit that has not previously been extensively sampled.
Stratospheric aerosol mass and latitudinal distribution of the El Chichon eruption cloud for October 1982
Authors: McCormick M. P. , Swissler T. J.
Published: February 2008

A coordinated aircraft flight mission to determine the spatial distribution and aerosol characteristics of the El Chichon‐produced stratospheric material is described. The mission covered 46°N to 46°S in October‐November 1982. Rendezvous with balloon‐, aircraft‐, and satellite‐borne measurements were accomplished. This paper presents the aircraft lidar data from the flight mission. From these data, the global stratospheric mass of the material produced by the El Chichon eruptions of late March/early April 1982 is estimated to be 12 megatonnes (1.2×1013 gm). The bulk of this material nearly 7 months after the eruptions resided between latitudes of from 5‐7°S to 35‐37°N, and was concentrated above 21 km in a layer peaked at 24‐25 km. In this latitude region, peak scattering ratios at λ = 0.6943 µm were approximately 24. Peak values over the latitudes 30‐45°S were 2 to 3 with the layer spread smoothly from 15 to 25 km. Peak scattering ratio values over latitudes 40‐45°N were between 7 and 13 with the layer residing mainly between 20 and 25 km.
Long‐duration Pc5 pulsations observed by geostationary satellites
Authors: Nagano H. , Araki T.
Published: February 2008

Using magnetic data from GOES 2 and 3 geostationary satellites for the year from June, 1979 to May, 1980, we found five Pc5 events which lasted longer than five hours. All these Pc5 pulsations were compressional oscillations occurring during the daytime in the recovery phase of large magnetic storms. The amplitude of the pulsations observed by GOES 3, which was located near 5°N magnetic latitude, was larger than those observed by GOES 2 near 10°N. The source region for the Pc5 waves seems to be limited in latitude and extended in longitude. The mean wave period was longer in the morning and evening than near noon; moreover the period changed quasi‐periodically with the average period of about one hour. This fact may indicate a Doppler shift in frequency due to the motion of the source or a variation of plasma density at the source.
Correlated particle and magnetic field observations of a large‐scale magnetic loop structure behind an interplanetary shock
Authors: Sanderson T. R. , Marsden R. G. , Reinhard R. , Wenzel K‐P. , Smith E. J.
Published: February 2008

We present one example of correlated particle and magnetic field observations of a large‐scale magnetic loop structure taken from a survey of observations on ISEE‐3. Approximately 12 hours after the passage of the interplanetary shock of 11 December 1980 and directly after the passage of a discontinuity, bidirectional proton fluxes were observed for a period of 40 hours in the energy range 35—1600keV. In each of the eight logarithmically spaced energy channels, a three‐dimensional anisotropy analysis showed streaming along both directions of the magnetic field. During the same 40‐hour period, the magnetic field rotated slowly but steadily through approximately 180°, consistent with the passage of a loop structure. This event is unique, in that both the particle and field measurements are clearly consistent with the existence of a large‐scale loop, with extent greater than 0.5 AU. Our observations indicate that the particles are being injected into the loop sunward of the spacecraft, and appear as bidirectional fluxes in the outermost regions of the loop due to a combination of focussing and near scatter‐free transport.
The minimum mantle viscosity of an accreting Earth
Authors: Cooperman Stephen A.
Published: February 2008

The minimum mantle viscosity in an earth accreting from planetesimals is estimated. A plausible distribution of planetesimal sizes deposits enough energy to melt the outer nine‐tenths of earth's mass; however, vigorous convection keeps temperatures near the solidus. Viscosity is significantly lower than prevails now. The temperature‐dependent viscosity provides self‐regulation so there is a continuing balance between accretional energy input and heat transfer out. This allows calculation of the minimum viscosity necessary to transfer out heat by a Nu/Ra‐number relation. Typical viscosities are 10−1 to 106 m²sec−1, lowest at mid‐accretion when the mass growth rate is largest. Terrestrial planets are compared, and minimum iron descent times to central lithospheres are calculated.
Phosphine photochemistry in Saturn’s atmosphere
Authors: Kaye Jack A. , Strobel Darrell F.
Published: February 2008

The phosphine photochemistry on Saturn is studied with a 1D photochemical model. The PH3 concentration is rapidly depleted with height (scale height 3.5 km) in the upper troposphere. Formation of P, a probable precursor of P4, (a potential red chromophore in the atmosphere), is highly improbable unless the rate constant for the recombination reaction PH + H2 + M → PH3 + M is less than 10−41 cm6 molec−2 sec−1. Coupling of PH3 and hydrocarbon photochemistry, specifically the C2H2 catalyzed photodissociation of CH4, is important. Column production rates of the organophosphorus compounds CH3PH2 and HCP of ∼3 × 108 cm−2 sec−1 are predicted, with potentially observable column densities of >1 × 1017 cm−2.
On the plasma conditions at the dayside magnetopause of Saturn
Authors: Lanzerotti L. J. , Maclennan C. G. , Lepping R. P. , Krimigis S. M.
Published: February 2008

The energy densities ϵP of the low energy ions measured by the Low Energy Charged Particle (LECP) experiment on Voyager 1 and 2 are compared to the magnetic field energy densities derived from the magnetometer (MAG) instrument during the crossing of the dayside Saturn magnetopause. The ratios of the proton to magnetic field energy densities are ≳0.5 during the Voyager 2 crossing when the magnetopause was at ∼18 RS. During the Voyager 1 crossing of the magnetopause at ∼23 RS, the ratios were ∼0.1, although they approached one as the spacecraft entered the region near 18 RS. The observations show that the dayside Saturnian magnetopause can at times have high beta plasma conditions, similar to the situation found at Jupiter.
Long‐path absorption measurements of tropospheric NO2 in rural New Zealand
Authors: Johnston P. V. , McKenzie R. L.
Published: February 2008

Tropospheric concentrations of nocturnal NO2 measured at our rural site in New Zealand (45°S, 170°E) are presented. We also describe the long path spectroscopic absorption technique used. The system features a beam splitter just before the exit slit of a scanning monochromator, and the broad spectral band signal seen at a second detector is used to remove the effect of amplitude modulations caused by atmospheric flicker. A signal ratioing technique produces nearly 2 orders of magnitude improvement in this noise. With a one hour observation period detection thresholds of 20 ppt have been achieved from absorptions over a 9.2 km path. The results display a wide range of mixing ratios from the detection threshold, up to in excess of 1 ppb on isolated days. A strong absorption feature at 442.6 nm is identified as a water vapour absorption, and the absorption cross section is found to be (3.1±0.3) × 10−26 cm² molecule−1 at 0.5 nm resolution.
Spectral analysis of 10m resolution scalar velocity profiles in the stratosphere
Authors: Dewan E. M. , Grossbard N. , Quesada A. F. , Good R. E.
Published: February 2008

Vertical profiles of scalar horizontal winds have been measured at high resolution (10m) in the 13 to 37 km region of the stratosphere. This resolution (at that range of altitude) represents the state‐of‐the‐art, and is unique. Our goal was to ascertain whether or not the internal waves of the stratosphere behave consistently with the Garrett‐Munk model which was originally created for oceanic internal waves. The power spectral densities (PSD's) of five profiles are presented and it is found that (a) they closely fit a straight line on a log‐log graph even to wavelengths as small as 40m, and (b) the average slope is −2.7 ± .2 (standard error = 0.1). We conclude that (a) stratospheric internal waves obey the Garrett‐Munk model for vertical wave numbers, and (b) there is no statistically significant evidence for a break in the curve at high wave numbers when due allowance is made for aliasing effects.
Measured vertical motion and converging and diverging horizontal flow of the midlatitude thermosphere
Authors: Biondi Manfred A.
Published: February 2008

Interferometric measurements of nightglow 630.0 nm doppler shifts and widths have yielded determinations of the meridional, zonal and vertical velocities and the temperature in the midlatitude thermosphere during the Priority Regular World Day 18 May 1983. Both the meridional and zonal velocities exhibit a diverging flow in the early night, changing to a converging flow in the later night. Associated with this are apparent, large vertical velocities (20‐30 m/s), upward in the early night, downward in the later night and back upward at the end, which also correlate with decreases and increases in the neutral temperature. While the sense of these observed effects is in agreement with the behavior predicted by existing hydrodynamic models of thermospheric flow, the magnitudes are either much larger (vertical velocities) or much smaller (temperature changes) than the model predictions.
Stratospheric sources of CH3CN and CH3OH
Authors: Murad Edmond , Swider William , Moss Robert A. , Toby Sidney
Published: February 2008

A common source is suggested for the acetonitrile (CH3CN) and methanol (CH3OH) observed in the stratospheric ions [CH3CN·H+·(H2O)n] and [CH3OH·H+·(H2O)n)]. Our chemical scheme originates with the three‐body association of HCN and CH2O. Rate constants needed to explain the observations are estimated. An astrophysical application is briefly noted.
Voyager 1 evidence for ion‐cyclotron instability in the vicinity of the Io plasma torus
Authors: Thorne R. M. , Scarf F. L.
Published: February 2008

A pronounced enhancement in low frequency wave activity was observed as Voyager 1 traversed the Io plasma torus. Wave intensification was particularly strong in the frequency range below the proton gyrofrequency. The data are interpreted as evidence for the excitation of ion‐cyclotron waves over the same radial range, L ≳ 6, where energetic ring current ions exhibit a pronounced depletion in phase space density owing presumably to strong pitch‐angle scattering loss to the atmosphere. While the average wave intensity observed by Voyager was typically an order of magnitude smaller than the level E′SD ²/Δf ∼ 10−7 to 10−6 (v/m)²Hz required for strong diffusion there were several prolonged intervals where the waves surpassed this critical value. Because the Voyager trajectory was far from the predicted source region (λ ≳ 15°) for ion‐cyclotron instability, the lower intensity of most waves reaching the spacecraft could be evidence for significant resonant absorption by thermal electrons and ions in the torus. If the more intense emissions, observed intermittently by Voyager, are representative of waves in the high latitude source region, the resulting pitch‐angle scattering would be rapid enough to explain the observed energetic ion losses and the excitation of intense Jovian auroral emissions of field lines passing through the torus.
Archean mantle fractionation
Authors: Condie Kent C.
Published: February 2008

Nd isotopic data require that most Archean igneous rocks are derived from depleted or undepleted mantle sources while geochemical model stuides necessitate enriched sources for most Archean tonalites. This apparent contradiction can be reconciled if the enriched sources are produced by short‐lived (≤150 m.y.) enrichment of depleted sources. Extensive depleted mantle reservoirs were probably produced during early degassing of the upper mantle (≥4 4 b.y. ago) and complementary enriched reservoirs collected at the base of the lithosphere. Sources for tonalites may be produced from short‐lived enrichment of basalt above convective downcurrents by metasomatic and magmatic components derived chiefly from depleted mantle and by degassing of sinking, short‐lived komatiitic lithosphere.
Estimates of long‐term probabilities for future great earthquakes in the Aleutians
Authors: Jacob Klaus H.
Published: February 2008

We compute probabilities for future great earthquakes in the Aleutian arc. Probability distributions are fitted to recurrence periods of great Aleutian events (Mw ≥ 7.8) since 1788. Given a probability distribution and date of the last great earthquake in each arc segment, time‐dependent conditional probabilities are determined for future periods of interest. We obtain for the next two decades high probabilities (99 to 30%) for great earthquakes in the Shumagin, Yakataga, Unalaska and Kommandorski seismic gaps. These probabilities are higher than for any other assessed region of the U.S. believed to be capable of great earthquakes. Low probabilities (17 to 9%) are found for segments that ruptured most recently in 1965, 1964 and 1957. Recurrence periods for great earthquakes measure on average about 80 years but vary substantially. Whether recurrence periods for great Aleutian earthquakes follow a normal, log‐normal or any other probability distribution is not resolved because in most arc segments the known seismic record embraces at best one or two recurrences. The resulting uncertainty affects the magnitude of estimated probabilities, especially in seismic gaps that have not ruptured for a long time. In some instances a normal distribution yields a three times higher probability than the corresponding log‐normal distribution.
A search for formic acid in the upper troposphere: A tentative identification of the 1105‐cm−1 ν6 band Q branch in high‐resolution balloon‐borne solar absorption spectra
Authors: Goldman A. , Murcray F. H. , Murcray D. G. , Rinsland C. P.
Published: February 2008

Infrared solar absorption spectra recorded at 0.02‐cm−1 resolution during a balloon flight from Alamogordo, N.M. (33°N), on March 23, 1981, have been analyzed for the possible presence of absorption by formic acid (HCOOH). An absorption feature at 1105 cm−1 has been tentatively identified in upper tropospheric spectra as due to the ν6 band Q branch. A preliminary analysis indicates a concentration of ≈ 0.6 ppbv and ≈ 0.4 ppbv near 8 and 10 km, respectively.
El Chichon volcanic debris in an Arctic tropopause fold
Authors: Shapiro M. A. , Schnell R. C. , Parungo F. P. , Oltmans S. J. , Bodhaine B. A.
Published: February 2008

A research flight with the NOAA WP‐3D aircraft revealed evidence for stratospheric‐tropospheric exchange within the Arctic through tropopause folding on the flank of the polar vortex. Observations showed descent of the tropopause and of stratospheric ozone to 700 mb along the west coast of Greenland. Measurements of condensation nuclei and analysis of high volume impactor samples documented the presence of volcanic debris probably from the 1982 El Chichon eruption, including H2SO4 droplets, within the polar vortex and associated tropopause fold.
Brominated organic species in the Arctic atmosphere
Authors: Berg Walter W. , Heidt Leroy E. , Pollock Walter , Sperry Paul D. , Cicerone Ralph J. , Gladney Ernest S.
Published: February 2008

Measurements are reported of four gas‐phase, brominated organic species found in the Arctic atmosphere during March and April 1983. Volume mixing ratios for CH3Br, CH2BrCH2Br, CHBr3, and CH2Br2 were determined by GC/MS analysis from samples taken Arctic wide, including at the geographic North Pole and during a tropopause folding event over Baffin Bay near Thule, Greenland. Methyl bromide mixing ratios were reasonably constant at 11 ± 4 pptv while the other three brominated organics showed a high degree of variability. Bromoform (2 to 46 pptv) was found to be the dominant contributor to gaseous organic bromine to the Arctic troposphere at 38 ± 10% followed by CH2Br2 (3 to 60 pptv) at 29 ± 6%. Both CH3Br and CH2BrCH2Br (1 to 37 pptv) reservoirs contained less than 20% of the organically bound bromine. Stratospheric samples, taken during a tropopause folding event, showed mixing ratios for all four species at levels high enough to support a stratospheric total volume mixing ratio of 249 pptv Br (888 ngBr/SCM).
Tropospheric circulation patterns during the Arctic Gas and Aerosol Sampling Program (AGASP), March/April 1983
Authors: Raatz Wolfgang E.
Published: February 2008

Tropospheric circulation patterns existing over Eurasian industrial areas and over the Arctic during the Arctic Gas and Aerosol Sampling Program (AGASP), March/April 1983, are described. It is shown that rapid and organized transport of aerosols takes place within transport zones from Eurasia into the Arctic, and that these transport zones are part of distinct and quasi‐persistent circulation patterns.
Generation of large scale potential difference by currentless plasma jets along the mirror field
Authors: Serizawa Yoichi , Sato Tetsuya
Published: February 2008

A new mechanism of producing auroral electrons is proposed. Field‐aligned plasma jets, presumably generated by magnetic reconnection in the magnetotail, give rise to charge separation along the mirror field whereby electrons are accelerated by the parallel electric field. The analysis shows that the potential difference can be expressed by eΦ=W∥ i (1‐1/γ)R/(1+R) where W∥ i is the ion parallel flow energy, γ is the mirror ratio and R is the ratio of the electron to ion temperature. In the magnetotail, W∥ i≃10keV, R≃0.2∽0.5 and γ≃10³, so that the potential drop can reach several kV which is reasonable to make auroral electrons.
Abundances and spectra of suprathermal H+, He++ and heavy ions in a fast moving plasma structure (plasmoid) in the distant Geotail
Authors: Gloeckler G. , Scholer M. , Ipavich F. M. , Hovestadt D. , Klecker B. , Galvin A. B.
Published: February 2008

Rest frame distribution functions have been deduced for 3 to 150 keV/amu H+, He++ and (Q≥3) ions (Q is the charge state) during a 16 min particle intensity increase in the distant magnetotail (>200 RE) using data from the University of Maryland/Max‐Planck‐Institut ULECA sensor on the ISEE‐3 Geotail Mission. This event was characterized by isotropic electron distributions and has been identified as a tailward moving plasmoid. We show that these suprathermal ions are convected nearly tailward at an average speed of 1000±50 km/s. From the measured dependence of distribution functions on velocity v, f(v) ⧜ exp(−v/v o ), we derive a number density ratio for n He ++ /n H + of 0.033±0.003 and for n(Q≥3)/n He ++ of 0.057±0.010, indicating that the solar wind is a dominant plasma source for these ions and that they are likely to be accelerated by a velocity dependent process. The energy density of these suprathermal ions is 150 eV/cm³, accounting for a large portion of the total pressure. Our observations combined with typical values for the thermal plasma in the near and far plasma sheet suggest that adiabatic cooling of the plasma has taken place as the plasmoid propagates tailward and expands, and indicate a crosstail expansion speed of ∼80 km/s.
Properties of SiO2 in a high‐pressure fluorite structure phase
Authors: Carlsson A. E. , Ashcroft N. W. , Williams A. R.
Published: February 2008

The equation of state and volume‐dependent band gap are calculated for SiO2 in the fluorite crystal structure. The equation of state is in considerable disagreement with recent shock magnetic compression results. Its form also suggests that if SiO2 is present in the earth's core in uncombined form it can only be so in relatively small amounts. The band‐overlap transition occurs at a density four times that of quartz at zero pressure.
Thermal ion composition measurements of the formation of the new outer plasmasphere and double plasmapause during storm recovery phase
Authors: Horwitz J. L. , Comfort R. H. , Chappell C. R.
Published: February 2008

Thermal ion composition measurements from several successive dusk sector passes by the DE‐1 satellite show the formation of the new outer plasmasphere and double plasmapause following a sharp decrease in geomagnetic activity. In less than one day after the magnetic activity decrease, the outer plasmasphere formed and consisted of cold, essentially Maxwellian plasma with ion composition and thermal energy characteristics generally similar to those of the inner plasmasphere, albeit at significantly lower densities. There is also evidence that at times the thermal O+ density is comparable to the H+ density within the plasmasphere.
On the reversal from “sunward” to “antisunward“ plasma convection in the dayside high latitude ionosphere
Authors: Jorgensen T. S. , Friis‐Christensen E. , Wickwar V. B. , Kelly J. D. , Clauer C. R. , Banks P. M.
Published: February 2008

Preliminary observations of dayside high latitude ionospheric plasma convection with the Sondrestrom incoherent‐scatter radar indicate that plasma can be observed to enter the polar cap region through rotational reversals at most local times between dawn and dusk and not just in a narrow region around noon. Assuming that rotational reversals are signatures of a solar wind‐magnetosphere interaction which drives magnetospheric convection, the observations indicate that this interaction occurs over a longitudinally wide area of the dayside magnetosphere. The observations also show that the distribution of F‐region plasma in the polar cap is dependent on ionization sources anywhere between dawn and dusk in the dayside high latitude ionosphere.
The influence of the interplanetary magnetic field Y component on ion and neutral motions in the polar thermosphere
Authors: McCormac F. G. , Smith R. W.
Published: February 2008

Neutral thermospheric winds and ion‐drifts at F region heights, observed at Longyearbyen, Spitsbergen (78.2°N, 15.6°E, 75°Λ) show a definite dependence on the sign of the interplanetary magnetic field Y component (IMF By). The neutral and ion measurements were made near winter solstice in the period 1979 to 1983 and were derived from optical interferometric observations of the Doppler shift of the oxygen emissions, OI 630 nm and OII 732 nm respectively, which occur in the aurora and airglow. The hourly averaged components of the wind and ion drift in the magnetic zonal direction were found for the 4 hour period spanning magnetic local noon. These zonal components were both westward when IMF By was positive, the neutrals reaching half the zonal speed of the ions. When IMF By was negative, the average zonal ion drift was eastwards but the neutral wind had a less symmetrical response, reaching only one sixth of the averaged ion zonal speed. These observations demonstrate that in general the ion convection is well coupled to the neutral thermosphere on the dayside at high latitudes but that clockwise vorticity is more readily generated in the northern hemisphere than anticlockwise vorticity.
Recent global changes in sealevel
Authors: Lambeck Kurt , Nakiboglu S. Mete
Published: February 2008

Tide gauge records indicate that a global rise in sealevel has occurred over the past 80 years at a rate of about 1.5 mm yr−1. Because of the poor geographical distribution of the tide gauges, this rise may be partly a consequence of a redistribution of water in the oceans without there being an increase in volume of the oceans. A principal contribution to this redistribution arises from the ongoing rebound of the crust to the melting of the Pleistocene ice sheets, a contribution that is of global significance even far from the limits of the original ice sheets. Model calculations indicate that this contribution may explain between 30 and 50% of the published estimates of the secular rise in sealevel.
Measurement and theory of the spatial distribution of excitation by high‐current electron beams injected into the ionosphere
Authors: Kofsky I. L. , Villanucci D. P. , Sluder R. B. , Chamberlain M. T. , Chang C. L. , Ko K. , Papadopoulos K.
Published: February 2008

Spatial distributions of energy deposition rates in EXCEDE Spectral's 3 keV, 7 A electron beam injection at E region altitudes derived from onboard photographic images of the air fluorescence are presented and compared with a time‐dependent computational model of the collective beam‐plasma interaction. The volume excitation rates decrease with a scale length of order 1 m near the rocket, are ∼2 orders of magnitude greater than predicted from single particle transport calculations, and at fixed distances from the accelerator vary by less than a factor 3 over an ambient density range of at least 40. The data are consistent with a discharge model in which the driving beam plasma instability is an absolute hydrodynamic instability with energy deposition controlled by trapping and axial dimension by ambipolar expansion of the plasma.
Simultaneous observation of the plasma sheet in the near Earth and distant magnetotail: ISEE‐1 and ISEE‐3
Authors: Scholer M. , Gloeckler G. , Hovestadt D. , Ipavich F. M. , Klecker B. , Baker D. N. , Baumjohann W. , Tsurutani B. T. , Zwickl R. D.
Published: February 2008

We present particle data from the spacecraft 1981‐025 and 1982‐019 at geosynchronous orbit (6.6 RE), from ISEE‐1 in the near‐earth geomagnetic tail and from ISEE‐3 in the distant geomagnetic tail at ∼ 130 RE obtained during the first half of March 22, 1983. The spacecraft observations are supplemented by ground‐based magnetograms from near local‐midnight stations. Two substorm particle injections were detected at ∼ 0715 and 0806 UT at geosynchronous orbit. At the same time suprathermal plasma sheet protons are observed at ISEE‐1. Multiple entries and exits into and out of the plasma sheet are recorded at ISEE‐3 in the distant tail. A substorm recovery is indicated by a poleward leap of the substorm electrojet at 0900 UT. After 0900 UT ISEE‐1 and ISEE‐3 entered the plasma sheet simultaneously within a few minutes. At the boundary of the recovering plasma sheet strong earthward streaming (ISEE‐1) and tailward streaming (ISEE‐3) suprathermal protons are observed, indicating that the two spacecraft were on opposite sides of the particle source. This represents the first measurement of ion beams at the plasma sheet boundary occurring simultaneously in the near‐earth region and in the deep tail flowing in opposite directions.
Detailed examination of a plasmoid in the distant magnetotail with ISEE 3
Authors: Hones E. W. , Birn J. , Baker D. N. , Bame S. J. , Feldman W. C. , McComas D. J. , Zwickl R. D. , Slavin J. A. , Smith E. J. , Tsurutani B. T.
Published: February 2008

A detailed description of a plasmoid is presented based on plasma electron data, energetic particle data, and magnetic field data from ISEE 3. The plasmoid, 75‐150 RE long, traveling tailward at 500‐1000 km/sec, appeared at ISEE 3, ∼220 RE down‐tail, 27 minutes after a very strong intensification of the auroral electrojet was recorded at several ground stations. The plasmoid was overlaid by a "separatrix layer" within which energetic particles, probably originating at a near‐earth reconnection region, streamed freely tailward along the field lines, the slower particles being encountered deeper within the layer. The plasmoid contained plasma of uniformly high temperature and its boundary was ≲ 1 RE thick.
The two‐lobe structure of the distant (X ≥ 200 Re) magnetotail
Authors: Tsurutani B. T. , Jones D. E. , Sibeck D. G.
Published: February 2008

The results of an analysis of ∼ 8 months of ISEE‐3 data to determine the structure of the distant tail at distances from X = 60 to 238 Re are presented. It is determined that the tail has a two‐lobe structure with embedded plasmasheet. No evidence of filamentary structure was found. From the second deep tail pass data, it is determined that at 200 to 238 Re, the maximum thickness of the plasmasheet at its center is ∼ 9‐15 Re, similar to near‐earth observations. The total north‐south dimension of the tail is ∼ 53‐59 Re. From an analysis of the first deep tail pass data, the east‐west dimension of the tail is determined to be ∼ 45 Re. Maximum tail deviations in the north‐south direction are only ∼ 6°, as measured from the earth.
On the relationship between the sea surface temperatures in the equatorial Pacific and the Indian monsoon rainfall
Authors: Khandekar M. L. , Neralla V. R.
Published: February 2008

There has been a resurgence of studies relating to Sea Surface Temperature (SST) variations in the equatorial Pacific and variations in atmospheric flow patterns over tropical as well as over middle latitudes. In this note, the SST variations over the equatorial eastern Pacific and the variations in the Indian monsoon rainfall (June ‐ September) are re‐examined with particular reference to drought and flood years. Our analysis reveals that major drought (flood) years are associated with warmer (cooler) than normal SST values before and after the monsoon season. A possible connection with a feedback mechanism between the SST variation in the equatorial Pacific and the monsoon rainfall over India and vicinity is hypothesized.
The EUV spectrum of H2O by electron impact
Authors: Ajello J. M.
Published: February 2008

We present the vacuum ultraviolet (VUV) spectrum of H2O produced by electron impact at 200 eV. A total of 25 spectral features is identified at a resolution of 0.5 nm over the wavelength range of 40 to 280 nm. Absolute emission cross sections were measured for each of these features. These features are all attributed to excited states of the dissociation products (H, O, O+). The Lyman‐α feature which is the brightest spectral feature for electron induced fluorescence of H2O from the UV to near‐IR has a cross section of 6.3 ± 1.0 × 10−18 cm² at 200 eV and contributes 74% of the total measured emission cross section in the EUV.
Mobility of water ice on Callisto: Evidence and implications
Authors: Spencer J. R. , Maloney P. R.
Published: February 2008

Voyager images of Callisto reveal evidence for the accumulation of a bright volatile, presumably water ice, on north‐facing slopes in the north polar region. The geometry of these accumulations suggests that ice migration in Callistoan high latitudes is dominated by thermal sublimation, controlled by insolation‐dependent surface temperature contrasts. Such sublimation‐dominated migration may result in the cold‐trapping of most of the surface ice in discrete high‐albedo regions.
Computation of tsunami amplitudes resulting from a predicted major earthquake in the Shumagin Seismic Gap
Authors: Kowalik Zygmunt , Murty T. S.
Published: February 2008

A time‐dependent two‐dimensional numerical model was developed to study the generation and propagation of a tsunami resulting from a major earthquake predicted to occur in the Shumagin Seismic Gap area of the eastern part of the Aleutian Island chain. The grid size is approximately 28 km in the latitudinal direction and 36 km in the longitudinal direction. The leading wave of the tsunami took only about three hours to arrive at the southern British Columbia coast and the northern part of the coast of the state of Washington. On the other hand, it took about eight hours to propagate into the Bering Sea. Two important results emerged from this study. The tsunami waves show very strong directionality, and the presence of the so‐called lateral waves can be inferred. In the deep ocean, tsunami amplitudes up to one meter appear to occur. To deduce the detailed distribution of the tsunami amplitudes at the coast, the present large area model has to be coupled to a coastal model which uses either finer rectangular grids or irregular triangular grids.
Geothermal exploitation and the decline of the Rotorua Geothermal Field Rotorua, New Zealand
Authors: Turner Gary J.
Published: February 2008

Within the past five years all the groups of continuously flowing chloride springs in Whakarewarewa have had some interruption to, or cessation of, flow. This indicates that the geothermal field is in decline. An historical survey establishes that formerly the response time of the springs to minima in cumulative deviation of rainfall was about 8 years consistent with an analogue model of the field. The recent response time, less than one year, is consistent with the model only when the effects of exploitation are included, indicating that withdrawal from wells is causing a major decline in the field.
Three‐dimensional adjustment of trilateration data
Authors: Sung Li‐Yu , Jackson David D.
Published: February 2008

We adjusted the three‐dimensional locations of the monuments in the USGS Hollister trilateration network to fit line length observations observed in 1977. We used a Bayesian approach, incorporating prior elevation estimates as data in our adjustment procedure. We found no significant discrepancies in the measured line lengths, but significant elevation adjustments (up to 1.85 m) were needed to fit the length data.
A search for presolar organic matter in meteorite
Authors: Yang Jongmann , Epstein Samuel
Published: February 2008

The D/H ratios and the 13C/12C ratios of acid‐insoluble organic matter of 4 meteorites, Ochansk (H4), Plainview (H5), Gladstone (H6) and Odessa (IA), were measured, δD values for hydrogen extracted by stepwise combustion were negative, down to −280‰. δ13C values were also negative except in the case of the carbon coming off at the highest temperature steps for Plainview and Odessa meteorites. The concentrations of 13C‐rich carbon were 3‐5 orders of magnitude smaller than those found in Murchison meteorite, suggesting that relic grains of stellar condensates were mostly destroyed in the meteorites examined.
Surface sulfur measurements on stratospheric particles
Authors: Mackinnon Ian D. R. , Mogk David W.
Published: February 2008

The surface chemistries of three particulate samples collected from the lower stratosphere have been determined using a Scanning Auger Microprobe (SAM). These samples are typical of the most abundant natural and anthropogenic particles observed within the stratosphere in the >2µm diameter size fraction. Successive sputtering and analysis below the first few adsorbed monolayers of all particles shows the presence of a thin (<150A) sulfur layer. These sulfur regions probably formed by surface reaction of sulfur‐rich aerosols with each particle within the stratosphere. Settling rate calculations show that a typical sphere (10µm diameter) may reside within the aerosol layer for ∼20 days and thus, provide a qualitative guide to surface sulfur reaction rates.